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Magpick user manual

1. Figure 37 Some profile data recorded with turns the goal is to remove them keeping data in polygon Note that you can adjust polygon by selecting its nodes and add new nodes by right clicking on 1ts border while polygon is selected for editing You can add multiple polygons Note that initially line names are assigned as they were during the survey For instance Profile browser dialog may look like shown on picture 40 To start profile splitting all profile views must be closed Proceed to the Profiles Cut profiles menu from the grid window as it is shown on picture 41 To start profile splitting all profile views must be closed Proceed to the Profiles Cut profiles menu from the grid window as shown on picture 41 If any of the profiles views are still open program will post a warning picture 42 If this is the case close all profile windows and repeat Profile cutting dialog will appear 1 How to split this tells the program what part of the profile lines to keep Possible selections are inside and outside of polygon s and Split by distance First two options require polygon to be drawn on the map last option works the same way as distance split in the profile loading 2 Split distance m This is only available if Split by distance is selected above In this mode program detects gaps
2. Central meridian degrees 123 00 Base projection parameters central meridian and scale factor Scale factor 0 9996 for UTM 0 999600 False Northing m 0 00 False northing and easting to be added Note that if you want to cut coordinates these values should be negative False easting m 0 00 Note Nortnihg and Easting are added to projected values Load Save UTM calculator 7 Longtitude 123 309 Ok _cancet_ latitude 3110 14 5 Lon Lat format deg min sec N Enter here Lat Lon of the point to be projected hing aaezo follow format specification for example if A EA format deg min sec enter 3 numbers separated Easting 452351 92 by spaces or read here result of UTM gt Lon Lat Zone 10 Central meridian 123W Dr Read here UTM coordinates or enter UTM Lon Lat gt UTM UTM gt Lon Lat to be transformed in meters For inverse transformation make sure that central meridian is correct This invokes particular forward or inverse projection Figure 81 UTM setup and UTM calculator in magpick The following is an example of the data processing e Prepare your data in the form X Y field columns with northing easting and data Northings and easting may be in full or short form If they are full you should apply fa
3. aos Read here the results eg 20 25 Inclination deep angle Total field nT 49874 41 Declination and absolute value nT 4 Accept parameters for inversion If you wish to keep these parameters and use them for inversion purposes check k Cancel o _Cancel_ this button Figure 82 IGRF model in magpick Magpick has an embedded IGRF model and an external file with coefficients igrf dat The model was obtained from http www ngdc noaa gov The user may need to get a new file igrf dat from the site as soon as it becomes available Dialog 82 shows how the IGRF model can be used It gets called from Inversion IGRF model You should enter the data and geographical position The main magnetic field changes from point to point smoothly therefore the high precision of position and date is not required It is acceptable if you are in the 25 km range and within a few month from your place and date of measurements you can check how the field changes by entering different positions and dates The western longitude and southern latitude should have a negative sign As soon as you entered these values press Calculate button and read the results If you want to use result for an inversion have these values automatically appear in inversion dialog box check Accept parameters for inversion MagPick will store the last calculated values These values also affect reduction to the pole group This is list of typical problems
4. l z h 7 E He i y MEE Uf AA R AS H 4 y EA q at oe CA ERA ERPE AG ooo i i EXA SAO l i fz A A A as NA Se A ee es Figure 44 Result of profile splitting in polygon second split line 1 2 was split in two parts now new line names are 1_1 1 2 1 3 1 3 14 1_5 but not 1_1_1 etc In the case a line was not split its original name is used If this option is not selected the program simply remunerates lines Original line names are not available in this case Operation is carried in memory so results must be saved into a file at some point or saved as a magpick project After operation is complete the map will look like picture Now user can remove polygon as it is not needed anymore Launching profile view and profile browser yields the following new line names 80 Profile data transformations Profile Browser Xx gt 1 file Martinhal_201210_03 Survey INTERPOLATOR INT _1 file Martinhal_201210_03 Survey INTERPOLATOR INT _1 file Martinhal_201210_03 Survey INTERPOLATOR INT Mile Martinhal_ 201210_03 Survey INTERPOLATOR INT il Martinhal_201210_03 Survey INTERPOLATOR INT il Martinhal_201210_03 Survey INTERPOLATOR INT Martinhal_201210_03 Survey INTERPOLATOR INT Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR IN lt SubSet
5. 4 After inversion has been completed the results appear in the work sheet table and are plotted on the top of all maps with numbers For inversion based on the grid sign is used 5 The interpreter analyses the results and decides whether or not to repeat inversion with different parameters The interpreter can open output grids with synthetic and residual fields to estimate quality Then initial depth susceptibility etc can be changed and Run step is repeated 6 By repeating the above steps with different initial parameters the interpreter can get an idea how stable estimation procedure is and what are reasonable estimations and their errors If results are close to each other procedure is stable and location can be estimated If not the interpreter may re select or even abandon the area as non interpretable 7 After a number of inversions it is possible to discard all or part of the results obtained in a given window To do that go to Inverse Remove results Here there is a list with locations obtained in the particular window To remove select all or part and press Ok The work sheet and map views are altered to reflect new results table To find magnetic dipoles information about the Earth s magnetic field and orientation of the local coordinate system has to be provided These values have to be filled in using the Inversion parameters dialog box To understand what they mean refer to figure 86 Here is complete
6. Additional information comes in wide variety of formats like USGS DLG AutoCAD DFX DLG ArcInfo files etc It is beyond MagPick s abilities to support all this world of digital data Instead MagPick offers its own but very simple format for external features It is your responsibility to transfer your data into this format For example there is a way how to transfer essentially any picture presented as PostScript file into MagPick representation this is not easy involves outputting some simple form of PostScript and then parsing it and scaling with your own shell script But here is just a simple example which does not involve the transformation questions Do next e With your favorite ASCII editor in many cases it will be the ugly program called notepad create a new file say line dat e in this file type gt UTM GRAY 5 10 10 10 7 70 7 70 1 10 1 Oo ooo The sign gt should be in first position and you have to press the cartridge return after last string Save this file e In the map view go to Options Drawings press the button Add select Type of the file Lines press OK select your file line dat Then press OK once more e You should redraw the picture in order for the changes to take effect Go to Edit Redraw A fat grey rectangle appears at the left bottom corner of your map e It s probably too fat Use your editor in line dat again and change gt UTM GRAY 5 to gt UTM GREEN 0 Save file Redraw
7. Format SURFER BINARY cor If this box is checked then output files are added to the history list for easy access Set output format here Figure 83 Upward continuation dialog Because these operations can be numerically unstable you have an option of simultaneous upward continuation to cope with possible noise increase Again you may need several attempts to find the best result 15 3 Reduction to the magnetic pole and pseudo gravity transformation It was shown see for reference that total field anomalies can be reduced to anomalies on the magnetic pole if the direction of the Earth s magnetic field and the direction of object magnetization are known Observed magnetic field Field o gt cay A a Ss e Transformed to the pole magnetic field Pseudo gravity field PI9y 9nauSeu s ye aq Distance Ns O a Depth Figure 84 Relation between observed reduced to the pole and pseudo gravity fields Figure 84 shows the relation between the field measured at the middle magnetic latitude a at the magnetic pole b and the gravity field c from the same object Curve a has a complex shape and the real location of the object is somewhere between minimum and maximum The actual location depends on the Earth s field inclination and declination as well as magnetization direction of the object On the magnetic pole b the Earth s field is directed
8. 1 Start MagPick and load all information Start MagPick Before doing anything else go to Options Settings and make sure that Color map and Contours are not checked We are not going to use the map in this tutorial We will load the dummy grid it is worth checking file dummy grd with the ASCII editor Set coordinate grid steps to 100 m for X and Y Press Ok Now go to File Open and pick file dummy grd An empty grid appears on the screen The size might be to small Go to Options Size and set X cell Y cell as 5 and enlarge window to see whole area This is our empty map 234 Tutorial Now go to File Profiles Load list Select file lines 1st MagPick reports that 6 profiles were loaded in this case each profile is represented by its own file Press Ok You can now redraw the picture Edit Redraw If this is not what you wanted go to Options Settings click on Show profiles to invoke profile configuration dialog Here check Plot stack profiles enter Datasets to draw 1 enter Data scale 10 this is value magnetic field divided by before plotting Check as well Use fixed direction and enter Fixed direction azimuth 55 Choose Fill type Positive fill the color you like and uncheck Clip stack plot We are done press Ok and one more to close Common parameters You should see stack profile plot now Profile inversion window If you try to start an inversion procedure from the map window then the map data wi
9. 22 zooming map appearance map data limits map resolution mass estimation 137 netCDF format palette color palette export gradient gradient editor uniform pick picks automatic delete all delete one export export into BNA 36 export into DAT export into DXF export into magpick lines export into magpick points export with inverse UTM export with linear transform file structure rectangular show crosses 23 simple snap to grid polynomail trend Grids Profiles Potential field transformations 125 potential field transformations gradients 125 ill posed problem solution 125 pseudogravity 126 reduction to the pole 126 upward continue 125 printing convert to bitmap convert to PDF 178 Postscript Print to scale 176 printing via GS View 178 Using GSView 178 profile marker accept transformation result activate browse cutting ends cutting parts data data loading data operations data smoothing 67 data transformations description list file 242 INDEX direction discard transformation result easy load export handling in magpick linear data transformation list file examples list file format load with templates Middle line approximation operations with positions plot parameters position drag position shift position spline smooth position transformations project on direction resolution save acti
10. Delete Close AEE h Profile information Total samples 3390 Figure 45 New profile names Note names like 11_1 81 Profile data transformations 7 5 Profile data export It is possible to export data along profile lines at some user defined intervals Say water depth has to be saved each 10 meters along the line to be used later for presentation or some other data processing This can be done by using File Profiles Export menus as shown on the following screen shot 46 File Edit Inverse Options Oper New Open Save Profiles Load list Simple load Open pick Save Save pick Export Pick export Figure 46 Profile export menu The dialog 47 below controls profile export procedure Export data along profile lines x Profiles to export Selected profiles Font size 72 1 gt 100 Output format Magpick lines Color RED E Annotation type Data Mark size m lo Interval im fio Median smpl 5 aia i Channela i ips wa Decimals after dot DATA a Export File d data mark dat nn T Append to file I Save as Longitude Latitude UTM parameters Ok Cancel Figure 47 Profile data export control dialog Left part of the dialog controls what to export and has the following input fields 1 Profiles to export controls what to export Possible selections are selected
11. Distance to shift drag along profile 7 Distance to shift 90 deg to profile lo Distance to find direction ls File key v Line numbers names Note Distance to find direction can not be 0 Preview Color creen y Ok Cancel Figure 34 Profile XY dragging dialog e Then chose the color to plot shifted positions This allows you to preview the result of trans formation and compare it with the original positions Note that the stack is not plotted if you have a shift preview 1t may obscure all the picture e Finally specify the shifts along X and Y axis Units are the same as original position informa tion After you press the Ok button the program redraws a current map view any other maps you have to redraw by hand You now have a chance to compare the result of transformation with the original track If you want to repeat it you just do it again The previous result will be automatically discarded To accept changes go to Profiles Accept All original profile data is replaced with the transformed data only for profiles where you did transformations You must save the profile data or the result will be lost after you exit MagPick To discard transformation results go to Profiles Discard The grid view will be redrawn and transformed part will disappear 7 3 2 Spline smooth Similar to the profile data profile X Y positions also can be smoothed with a cubic spline A good example of
12. Leveling tie lines Profile spatial filtering x Model type Linear m1 m2 x m3 y X PRAE Channels hr Estimation type Least squares L2 z Preview color SPRING_GREEN Present results as Show as preview Figure 52 Profile polynomial background dialog 2 Present results as The options are Show as preview Difference grid model and Model replace with model Two last options were explained in the grid operation section Option Show as preview works the same way as Smooth option in the profile view it presents user result of the operation which can be accepted or discarded 3 Preview color Color name to be used for the preview graph in the profile window Once again L1 estimate can take considerable time therefore L2 is recommended in most cases When estimation is completed status dialog is displayed showing method used L1 or L2 and model fit If options Difference grid model or Model replace with model have been used operation is complete If option Show as preview was used user should inspect results in the profile window Go to New and select Profile view or All profiles in the window Typical view is presented on figure Here is original field shown with red line and result of the polynomial modeling with green line or what ever color was selected in the dialog It is recommend to browse through the rest of the profiles to ensure acceptable results After inspect
13. _ And see sample here You can create delete change color and data value for the nodes Nodes are clickable by mouse and can be draged There is also pre defined set of palettes Click right button to see the menu There are different menus o node and space FF Equalize colors Cancel 37 Cancel Requare magpick to do color equalization so each color occupies approximately the same space on the map between nodes Figure 10 Uniform and gradient palette setup MagPick has a flexible tool to deal with a gradient palette see figure 1O but uniform palette has the advantage ability of color equalization The goal of equalization is constructing of image where 29 Basic operation of MagPick single color occupies the same area as each other Equalization provides an enhanced color image and even small details can be seen immediately To cover this gap MagPick has ability to transform equalized color palette into gradient one To invoke these options click on Change palette button in the Common parameters dialog box You will be prompted for the type of palette you are going to use Then end up with either dialog figure 10 You can zoom part of the window if you wish To do so choose Edit Zoom You will see that the mouse cursor has a shape of a magnifying glass Press the left button and drag the mouse around area you would like to zo
14. c B ry Z g RE i o a o 2 o oO A E X1 Y1 Y D H 0 0 D 0 o o xk 0 H to Geographic projection East Figure 72 Rotation transformation in MagPick e Full UTM refers to the projected coordinate system on the left part of figure 72 Note that both full UTM numbers change when mouse cursor moves vertically or horizontally e Latitude Longitude refers to the actual geographical position of the point the same as in no rotation case While converting from longitude latitude the sequence is 1 Apply forward UTM or PROJ 2 Rotate the result 12 4 Using built in UTM transformation Projection settings are available from Options UTM setup or UTM PROJ setup They are also available while using Simple profile load or Template Profile load In the latter two cases MagPick tries to auto detect appropriate projection parameters based on actual data being loaded For Western longitude and Southern latitude entered values should be negative Figure 73 shows the UT M setup dialog in MagPick User should specify an ellipsoid name di rectly enter the ellipsoid parameters if ellipsoid is not listed central meridian scale factor normally 0 9996 for UTM 1 000 for Gauss Kruger latitude of origin 0 in most cases origin is on equator and False Northing and Easting as discussed above Note that ellipsoid should match geodetic datum used to record data For user convenience and easy
15. 156W 150W 35 027E 024E 030E 6 147W 150W 144W 36 033E 030E 036E 7 141W 144W 138W 37 039E 036E 042E 8 135W 138W 132W 38 045E 042E 048E 9 129W 132W 126W 39 OSIE 048E 054E 10 123W 126W 120W 40 057E 054E 060E 11 117W 120W 114W 41 063E 060E 066E 12 111W 114W 108W 42 069E 066E 072E 13 105W 108W 102W 43 075E 072E 078E 14 O99W 102W 096W 44 O81E 078E 084E 15 093W 096W 090W 45 087E 084E 090E 16 087W 090W 084W 46 093E 090E 096E 17 081W 084W 078W 47 099E 096E 102E 18 O75W 078W 072W 48 105E 102E 108E 19 069W 072W 066W 49 111E 108E 114E 20 063W 066W 060W 50 117E 114E 120E 21 057W 060W 054W 51 123E 120E 126E 22 051W 054W 048W 52 129E 126E 132E 23 045W 048W 042W 53 135E 120E 126E 24 039W 042W 036W 54 141E 138E 144E 25 033W 036W 030W 55 147E 144E 150E 26 027W 030W 024W 56 153E 150E 156E 27 021W 024W 018W 57 159E 156E 162E 28 015W 018W 012W 58 165E 162E 168E 29 009W 012W 006W 59 171E 168E 174E 30 003W 006W 000E 60 177E 174E 180W Table 1 Standard UTM zones 111 Geographic projection transformations UTM and PROJ 12 5 Using projections provided by PROJ library Starting with version 3 20 MagPick support Open Source Cartographic Projection Library PROJ PROJ is used in almost all Open Source
16. A lo Text color a Font size 10 1 4 _ gt 32 Annotation type Annotation text Figure 149 Text label annotation properties Here the user can adjust the following properties e Draw solid rectangle or not and define rectangle color e Draw border or not and define border color e Set border width in pixels User may want to set it above O for PostScript output Set label font size e Set annotation text Depending on Annotation type selection the following annotations are available 1 User text Any text user can type in the dialog Note that multi string annotations are available 2 Time stamp System automatically assigns text to be current date and time Text is updated each time map is drawn This is shown as H above on figurq148 3 UTM parameters Using current UTM projection parameters program prepares projection time stamp This is shown as F above on figurq 148 Note that if 2 or 3 is selected time or projection information remains in the dialog after 1 is selected thus allowing user to customize those values 202 Map annotations 25 1 2 Color Scale B This feature is available under Add color scale menu Color scale size can be adjusted manually after initial placement Color scale properties are shown on figure 150 Orientation rage y Level interval i Digits after dot bo M Use custom values Font size ae mi ee Annotation Magnetic
17. Grid data editing such as lifting or lowering parts of the grid Grid data transformations such as upward downward continuation gradient computation reduction to the pole Grid smoothing using relaxation technique and resolution increase using bi linear or spline interpolation Color palette export into GMT and SURFER formats 13 History and features of Magpick 2 4 Version 2 8 3 00 2004 2009 Some major improvements has been made during that period Read write SURFER 7 grids Floating map annotations These include color scales text north arrows scales stack scales polygons and lines The annotations can be saved into the file and transmitted this way between maps and projects Ability to call external programs for instance GMT utilities to smooth profile data Results are displayed and handled the same way as built in smoothing Another quick gridding method is added Ability to clip data using profiles is added Latitude and Longitude coordinate grid is added to the map views Export into GeoTIFF geocoded TIFF format is added Export to PDF is added via external programs ghostscript and gsview This enables Mag Pick to produce to scale paper output with appropriate annotations Quasi Analytic profile based signal computation has been developed Simplified version of profile inversion for two and more data channels was added This was done with help of maginvlib library The library itself was
18. To restrict the data do the following Under map window go to Edit Polygon then go with the mouse to the point 5800 2800 approximately Click the left button Draw a polygon as it is shown on figure 165 4 Close polygon by hitting the first point one more time If you clicked the left button by mistake the last node can be removed by a right click Choosing Edit Polygon removes current polygon completely As soon as you draw the polygon your profile inversion window changes too It shows only data inside the polygon try for example to draw very narrow polygon and see what happens Defining initial pipe location in XOY plan For a non linear inversion we have to define the initial location of the object In MagPick Simple pick serves for this Go ahead and set the pick as it is shown on 165 5 for the first try you even can set it close to anomalies Opposite to the dipole inversion pipe inversion allows just only one pipe at once for dipoles you can have several of them estimated simultaneously 235 Tutorial 1d ads 000 0 08 868Z E0 EZL9 15114 JOJE9Ipul SSaJBOJd 8 sas l JO S INSSI UUM JOBS 9 Lo 8186 b 6 BL LPSSOE 168679 OL 9OLZ LS BEBS N2 A ZA cx TA EN Buiyeoo adid 40 pesn eJep yu 0 UoBA Og Y LO 910 Z bo ase9 b L p6Sl SEbZOE 627579 8 Z 8BEZZ 2 8585 d LO 8PEZ Z PO 8072 b L 88 9L 8090 60 LSZ9 SL E9GZ 10 8595 d LO a0pO Z t0 aS8S t L EZ 9L pae4oe bl
19. Z of its geometrical location In addition a simple function to fit background field can be found Because of it method can be applied directly to the measured field without calculation of the residual field In general searching of the magnetic dipoles is an iterative process which requires knowledge of their initial positions MagPick uses the locations of the middle points of the simple picks as initial locations All picks done in the current map view are involved in the estimation If user does not pick any points the inversion procedure can not be started 16 1 Magnetic modelling based on grid data With a magnetic map loaded into the one of the map views the process of inversion involve following steps 1 Interpreter visually analyses all areas and makes a decision about the approximate number of dipoles The interpreter decides where to start and how to proceed through the area 2 Part by part the interpreter selects subwindows by means of the zoom facility The aim is to get a subarea with one or more clear magnetic anomalies Subwindows also can be zoomed into if needed 3 The interpreter does one or more simple picks to hit approximate locations of the magnetic dipoles Then Jnverse Run is invoked inversion parameters are set see description below and the program does iterations During this step the user interface is blocked and the inter preter has to wait until it finishes 128 Estimation of magnetic sources
20. in this case file selection dialog is displayed or Automatic list file name In this latter case the user is not prompted and the list file name is simply created from first data file name by appending extension st 7 Filter by signal signal column signal level There values are identical to thoise in the Simple Load dialog They control data acceptance based on signal level applicable for Geometrics cesium magnetometers Data with signal level below the threshold defined in the dialog is discarded When the user presses Ok the profile data is loaded into the program in the same manner as they are loaded using Simple Load The user may be prompted to define the list file name if this option was selected in the above dialog box 5 5 4 Operation with profiles on the map After loading a new object appears in the program list of the profiles This enables plotting of geometrical positions on the maps if this feature is enabled see figure B viewing of the profile data as linear graphs and allows putting marks on them Each profile can be in an active and inactive state This is shown by color An active profile is shown in the profile view window if any and highlighted on the map When you choose New in any window a small dialog box appears which allows choosing the type of view you want Depending on where you choose New in map window or in root window of the program there will be two or three choices They are 45
21. s gone Remove all picks you have done and make a new clean one 4 Saving and loading of pick file We certainly want to keep this information Go to File Save pick and select a file say pick out Press Ok Save Exit MagPick start it again and load the file bomb grd Go to File Open pick and select pick out We have it again You can interrupt your work save your picks and resume it later You might be interested in looking at the pick out file with an editor probably notedad Each string in this file represents a pick I will not explain all the fields in that string see the complete manual for that but here is what s important e Last number is always 0 000 you do not need it Two numbers before the trailing 0 000 horizontal X and Y position of the middle of the pick You are probably interested in this point 5 Notes about picking It s a tedious process if you have a large field You generally should not work with the whole map at once Instead zoom into different places to see them better pick anomalies there the close the zoom window and go to the next place Certainly you should cover the area gradually say west to east and north to south In some cases if shape of an anomaly is complicated a rectangular pick is not what you need you have to go with a simple pick The result of your picking is a table with X Y Z locations you want to check with digging or diving The pick file also hold
22. s magnetic field in the area we are working in There are some models and tables which can be used to find these values The well known IGRF program is one of them IGRF stands on International Geomagnetic Reference Field see for example IAGA Working Group V 8 1995 International Geomagnetic Reference Field 1995 revision Submitted to EOS Trans Am Geophys Un Geophysics Geophys J Int J Geomag Geoelectr Phys Earth Planet Int and others MagPick includes IGRF model for easy computation of Earth s magnetic field elements MagPick is capable of estimating of total magnetic moment of the object Dependence between magnetic properties and mass is quite complex and based on remanent magnetization Je and sus ceptibility K The last two values vary even for one kind of material Nevertheless MagPick tries to find mass based on these two values but results are not so good in many cases because of wide range for Jrem and xK This task is non unique it has two solutions So do not pay too much attention when you see some weird values for mass during MagPick operation Goal We will learn how to find the position and magnetization of the point source s if we have a map of magnetic field Files Use the file bomb grd from previous lesson We need parameters of the magnetic field for Hamburg Germany Trotar 49011 nT D 0 1 1 68 3 Here D denotes declination 7 denotes inclination Parameters of the object Je 0 24cgs Kk
23. the targets and updates map views e Undo Undo last deletion Up to 50 undo calls are available 16 4 Option of mass estimation In case of known K Jem and a given vector of total magnetisation an attempt to estimate the mass of the body can be made MagPick does it automatically after each inversion One should understand that mass estimations can be incorrect in many cases due to the difference between assumed and real magnetic properties of the object In some cases the problem can not be solved mathematically see below Nevertheless MagPick will always give two values for the mass which correspond two roots in a square equation In case the equation can not be solved the value of extremum of the quadratic function replaces both roots and a message is printed on the console Unix version In the last case a predicted value of J can be calculated and compared with the MagPick estimation The relative difference in arrears in the column Discr 16 5 Automatic estimation of magnetic sources You should note that the estimation procedure requires good deal of manual work It involves selec tion of the area of interest setting pick s by hand or by some simple procedures as rectangular pick or even autopick running estimation and inspection of results This should be repeated for all points of interest To avoid this MagPick has a simplified routine which allows it to interpret all anomalies at once It should be noted that the result
24. units below User than is responsible for selecting correct length to match the map 2 Scale units There are five available selections meters feet kilometers miles nautical miles This also controls scale annotation 3 Tics Controls how many white and black bars to use for the scale 4 Hight pxls Map scale hight in pixels The rest of the Map scale properties dialog is the same as for annotation label When scale is plotted in the postscript file MagPck appends annotation in form 1 xxxx to indicate paper scale of the plot 205 Map annotations 25 1 5 Polygon E This is not only an annotation feature but one of the tools as well Polygon allows data clipping using data in the inversion etc It is available under Add polygon menu User should set first polygon point by clicking left mouse button and then sequentially left clicking all remaining corners of the polygon To undo last corner press right mouse button To complete drawing left click the first point of the polygon Polygon appears on the screen and its properties become available the same way as for all other annotation types figure 153 Polygon properties xj Hatch Diagonal Border width lo MV Use polygon to clip data Ok Cancel Figure 153 Polygon properties dialog Here user can define polygon hatch if any fill and border colors as well as border width Check box Use polygon to clip data is important It allows
25. volume of the body cm In the case all distances are measured in cm then x in cgs units J em in gauss and J in nTesla 17 2 Basic inversion To estimate position and magnitude of the source we have to model the observed magnetic field Mathematically it means that function N Y TAROT riveted e i 0 has to be minimized Here is T observed magnetic field r points of observations total number N in case of the grid interpretation they are nodes of grid in case of profile interpretation they are points of actual measurements T expression of the magnetic field from M magnetic dipoles Generally the problem is non linear but can be divided in two steps a linear step to find J and a non linear step to estimate positions The flow of execution is the next First fix the positions of dipoles and estimate J Then fix J and improve the positions and so on Thus J are linear parameters and can be found in one step by inversion of the matrix AJ T In the case of one dipole A is the matrix 3 x N where N is number of data points and T is data itself Columns of A have meaning of the magnetic field calculated from the dipole with a unit magnetic moment sequentially along X Y Z axis This task is overdetermined and J can be found by simple least squares method MagPick uses this in the modification of the singular value decomposition In most cases there is a significant background regional field in the observed field which can
26. www remotesensing org libtiff is the Copyright c 1988 1997 Sam Leffler Copyright c 1991 1997 Silicon Graphics Inc GeoTiff library http www remotesensing org geotiff geotiff html QUIKGRID gridding software by Perspective Edge software http www galiander ca quikgrid under the terms of the GNU general license Info Zip compression software http www info zip org pub infozip license html under terms of Info Zip license 239 Tutorial 8 PROJ lib cartographic projection datum transformation software http trac osgeo org proj under terms of MIT license 9 LibCurl free and easy to use client side URL transfer library http curl haxx se libcurl under terms of MIT Xlicense References 1 B Yanovsky Magnetism of Earth Leningrad 1978 2 FGoltzman Physical experiment and statistical conclusions Leningrad 1982 3 Smith W H F and P Wessel Gridding with continuos curvature splines in tension Geophis cis vol 55 pp 293 305 1990 4 Watson D F ACORD Automatic contouring of raw data Computers amp Geosciences 8 97 101 1982 5 IAGA Working Group V 8 1995 International Geomagnetic Reference Field 1995 revision Submitted to EOS Trans Am Geophys Un Geophysics Geophys J Int J Geomag Geo electr Phys Earth Planet Int and others 6 Snyder J P 1982 Map projections used by the U S Geological Survey U S Geological Survey Bulletin 1532 313 p 7
27. 27 in US survey foot 118 12 6 4 California Zone 2 NAD 83 in US survey foot 119 Ed hae a 119 a rr 119 A 120 AS E AA oe Re a 120 ig aia they a 120 13 UTM Gauss Kruger transformation in magpick OBSOLETE 121 14 Earth s magnetic field model IGRF 124 125 EEE ER Ea ae Ra ew EERE ER Ge REESE ES 125 15 2 Synthetic horizontal and vertical gradients o o 125 ate 126 128 NAAA a Pe BAe oe ae e 128 snendcad Sead Sard Sead tracy se 131 16 3 Magpick worksheet results of inversions o o 133 ee IR AREA 134 16 5 Automatic estimation of magnetic SQUICES o 134 135 17 1 Solution of forward probleM o e e 135 A o a Gee Bue A a pare oe 136 lodo 137 8H AR EE RE OER ORE RG Ee ee eh eg aed 137 Soi a ah Wee aa ROH Be Rae Ge aa es ah Be Qe ee ee 138 18 Using single magetometer data for inversion in MagPick 140 Pio Cle Cte E Oe rosati 148 149 20 Estimating location depth and electrical currents for HVDC cables 155 RR ARA AAA AA AA o A 155 Si A 157 20 3 HVDC inversion Results 52 is rua A ee eS ESS 159 21 Pipe line Total Field and Analytic Signal data treatment 161 A a a a ee ee 161 21 2 Approximation formulas lt 4 162 AER IR 162 165 pata da 165 AAA AAA a d 170 22 2 1 MagPick Image Overlay o e 172 ih ede Rig Bi ias ARA 173 aR Ree ee Re ee Ee ee
28. 4 b A q are parameters to be estimated to approximate QAS curve xo is horizon tal location of the pipe line along the profile The method does not take into account possible variation in height along the data profile Parameter z is not used as depth program takes width of the approximated anomaly at certain user defined level instead The formula above serves for sole approximation purposes to avoid influence of the data noise which could be particularly substantial in case of Quasi Analytic signal To estimate width of the anomaly at certain level only first term of formula is used J x x9 22 therefore results are slightly different from direct measurements using data curve A x 2 For Total Field Ji x x0 z Jo x x0 2 x x0 22 x x0 27 5 Similar to the QAS formula Total field serves for approximation purposes not for inversion Parameters J1 J2 x0 z 5 a b Ty are to be estimated The second term of the formula Toti a x xo b x xo Tac J E Da 2 ry 20023 x x9 22 is used to estimate width at certain amplitude level therefore the best results are obtained for bell shaped total field data also called positive and negative monopoles 21 3 Data processing To start with inversion first draw approximate location of the pipeline using polyline feature see picture an an example This is important because 1 Program will
29. 8 GPS protocol Select appropriate protocol supported by your GPS device Four different protocols are supported by GPSBabel to upload waypoints Most tested is Garmin 9 Port Select appropriate port Some GPS receivers have USB connectivity some have serial RS 232 and some have both Which port should be selected depends how your GPS is con nected to the computer 10 GPSBabel executabl This file name should point to gpsbabel exe For Windows its is typically located in a subfolder of the Program Files folder For Linux you just could use name gpsbabel if the location is included in the path If wrong name is used or gpslabel location is not in the path no upload will take place After Ok button is pressed program saves GPX file first and then launches GPSbabel if requested Running progress bar with option to cancel shows that data is being transferred Note that serial connection is typically slow and it could take time to upload long way point list After transfer is completed success message 135 is shown 190 Target position export ET x GD cPsbabel successfully uploaded waypoints into GPS Figure 135 Waypoint upload success message If for some reason transfer cannot be completed error message similar to the message is displayed ME tt ex GPSbabel has Failed to upload waypoints into device Please check if GPS is connected and has correct mode GPSbabel message ERROR GPS_Packet_Read Timeout
30. Automatic pick s ac e coad 64 ibid daria A 37 Cea RSE AED 38 5 5 1 Profile loading 3 46 h4 ee ea GRP ER ERE ES See RHR EES 38 5 5 2 Simple profile load ooscorcirsroosrrar Ree ee ees 40 sh ae Sah Se See SR SS A SSS 43 Ck ER DER SE REER ES GASH A SSS 45 5 5 5 Parameters of the profile VieW o o eee eee 47 5 6 Latitude and Longitude coordinate grid 2 2 0 2 ee 49 3 PUM secs sare sos at gh dr aoe roa A a oR ee 51 1 6 Grid operations 6 1 Making grid out of profile data o o 000000008 6 1 1 Triangulation with linear interpolati0O o ae E EN A A A E A a det Pee Dee Pe e a 9 a 6 3 Create clip path we au ias AR AA RAR CALI AAA A A a we a ea R 6 5 Clipping grid file using profile information 200 6 5 1 Clipping the grid using triangulation o 6 5 2 Clipping the grid using profile data points o 6 6 Exporting grid data as XYZ file and mosaicking in MagPick 66 1 Export ito XYZ sac ee ee pra Se eR EEE RR AS EASES 6 6 2 Creating and overview map from number of grids 6 6 3 Exporting data from MagPick to Geoplot 3 00 experimental 7 1 Saving and re loading profile data o a A A e A AR IR E A a E 7 2 1 Cutting profile parts socios ocurre er eek eees 7 2 2 Removing turns from profile lines 7 2
31. Basic operation of MagPick Load profiles using template xj Available templates TYG MagLog INT with altimeter on sensor 1 TVG MagLog INT with altimeter on sensor 2 Add template Remove template Set all default templates Apply UTM on input positions in Lon Lat EGS yaa UTM parameters How to save list file Prompt user for a file 7 Filter by signal Signal column fo Signal level foo Ok Cancel Figure 17 Main load with template dialog e Grid view Create a normal window for map displaying That is the same as without profile loading If profile data is loaded at time map created MagPick creates a fake empty grid to allow viewing of their positions e Profile view This allows to see profiles as linear graphs one by one There are four possible types of presentation as T X T Y T d T p Where X and Y is local coordinates d distance along profile always starting from zero and p projection on user defined axis The last type of graph is possible when the profile view is opened from map view window with plotted direction of a new axis If there are several data sets in one profile file they are shown by curves of different colors All profile view windows share the same data global list of profiles When you are working with one window the results can appear on all the map windows All profiles in the window Profile inversion Show all profiles which cross the parent map window in the
32. Bt lt H ue i E 44 60m 43 28 61m 43 24 09m 43 26 39m 43 26 03m 43 26 31m 43 0 meters 100 3200 3300 3400 3500 3600 n 1 5000 X m Figure 48 Example of how exported data could be used to annotate profile lines 5 Decimals after dot DATA Controls resolution of saved data You might want to trim it to 1 if depth is exported The bottom of the dialog defines where to export the data and how represent position 1 Export file Press button to browse for folder and name 2 Append to file Append new information to the existing file It is particular useful in case of MagLog formats 3 Save as Longitude Latitude Perform inverse UTM transformation before exporting the data For MagLog formats this is done automatically but note that there should be sufficient number of decimal places to accommodate Longitude and Latitude 4 UTM parameters Shows projection parameters used to export the data Here is an example 48 how this feature could be used Here is sum of depth sensor and altimeter was exported each 100m as MagPick points marks Line number was also included in the export Resulting file was re loaded using Options Drawings menu It can be seen now that profile lines are annotated each 100 meters with water depth The same can be done with MagLog background survey plan file 8 Removing polynomial background for profiles and grids Starting with version 2 92 MagPick allows simple polynomial backgro
33. Change palette how to draw color map noaes calls dialog box Click on items to change feature parameters 9 Call dialog box to 6 Calls dialog to choose set contour isolines color sheme plot parameters 8 Set profile stack plot 7 Show small crosses at the ends of parameters calls dialog box the picks Figure 3 Common parameters dialog box Data min Data max User defined limits for plotting of the grid data Unless autoscale is checked color palette is scaled to that range all data above Data max is drawn with maximum color all data below Data min is drawn with minimum color This parameters has no effect if autoscale is checked Data min Data max have different meaning if you choose Wrap color scale Autoscale If checked the color palette is scaled to the real minimum and maximum of the data in the current window Note only the data into window is used to determine min and max Wrap color scale This provides a color scale wrapping and the ability to see fine details in the map It works like this say your data is in the range from 0 to 2000 You have set Data min 0 and Data max 200 This means that all the available color scale gets mapped into this range Now what happens when we need to map cell with value 201 It gets mapped the same way as a cell with value 1 And so on The map obtained in this way has ambiguous colors but allows more structure to be
34. Fast sequencing of these buttons can cause crash under X windows You also can select data directly from the list box by mouse Now we will show how shrink works select first line and go to Parameters Settings Uncheck shrink to canvas and set T scale as 1 and X scale as 0 1 Press Ok and go to profile browser Go thru profiles again Dou you see a difference Data is always presented in the same scale therefore it is easy to recognize large and small anomalies Check shrink again You can have as many profile windows as you wish Just go to File New to create them Add another file to the profile list We have file g 858g dat which is worth looking at Create new empty grid view we need it just to access File Profiles Simple Load Select g 858g dat now Choose split by LINE and data as BOTTOM_RDG Press Ok and press Ok again Answer Yes to Append to previous profile list The total number of profiles loaded is 102 now Create a new profile view the old one does not know you loaded new data Now you have both second one has very large numbers as X Y coordinates This creates a some problem that we will describe later You can browse two files with profile data now You can have as many files as you need Saving file list for future use What happens if you have 200 files Add them all one by one every time you need to load in formation No When you go to File Profiles Simple Load you have a check box Save
35. GIS projects such as GDAL OGR QGIS GRASS etc and covers almost every imaginable cartographic projection and datum transformation MagPick loads PROJ as dynamic library proj dll For MagPick Windows distribution proj dll and support files are included in the distribution for Linux version user is re sponsible for installing PROJ most modern Linux distributions have binaries available for simple install PROJ overlaps with the built in UTM projection originally used in MagPick code in fact it is not necessary to use built in UTM at all Figure 75 illustrates relation between built in UTM and and PROJ library Build in UTM Transverse Mercator only PROJ LIB All GIS projections in the world plus datum transformations Figure 75 Built in UTM and PROJ It is possible that in the future MagPick would drop built in UTM support and only PROJ would provide projection capabilities It is highly recommended that user downloads PROJ manual from its web site and at least gets accustomed to the common proj command line syntax because this is the way how projection pa rameters are defined in MagPick as well One of the key differences between built in UTM and PROJ is that latter actually defines two projections input data projection and internal MagPick projection The first one in most cases is trivial such as longitude latitude projection in WGS84 datum The second projection describes how data is represented in MagPick along with fals
36. No data received GARMIN Can t init comi Figure 136 Here GPSBabel message shows error information reported by GPSBabel In this partic ular case serial port COM1 was requested instead of USB After transfer is completed use your GPS navigation functions to navigate to the target locations 191 Anomaly plots with gnuplot 24 Creating anomaly plots with Gnuplot and including them in the Google Earth export file 24 1 Download and install Gnuplot Third party software is required download and install Gnuplot for Windows from For Linux use your distribution software managment system to install gnuplot If self extracting distribution file like gp46rc1 win32 setup exe is downloaded gnuplot will be installed in the folder C Program Filesl gnuplot If zip archive such as gp444win32 zip is downloaded its content should be manually extracted into separate folder such as C gnuplot and no further installation is required Path to the folder where gnuplot is installed is needed for MagPick to operate correctly 24 2 Keep protocol files and point magpick to the correct protocol folder During inversion user should enable protocol feature and keep protocol files in specially designated protocol folder Make sure Create protocol DAT file in the inversion folder option in the inversion dialog is checked Protocol folder selection also available from the grid Inversion menu as shown on figurd137 4 Magnetic map picking patch1_tf_as_
37. Profiles Smoothed field values All profiles Difference original smoothed values Active profile s Smoothed field values Active profile s Difference original smoothed values Ok Cancel Figure 54 Background field selection dialog number of intersections should be more that twice number of lines Here is an example say survey consist of N lines going South North and M tie lines going West East Total number of intersections are M x N Total number of lines is M N Therefore the condition is M x N gt 2 x M N This means that if N gt 6 then minimum number of tie lines M 3 4 After all intersections are computed minimization problem could be solved by linear least squares method or by robust L1 estimate It should be noted that problem formulated above does not have unique solution For instance if arbitrary spatial linear function or even simple DC offset is added to the profiles discrepancies at the profile intersections remain the same Therefore solution is non unique To resolve this problem the following treatment of the data is used 1 Prior to the leveling linear background of the data is computed It is assumed that even raw data can represent correctly linear geological trend in the given area Trend coefficients are stored for future use Due to complexity of the operation L2 least squares estimate is always used for the trend 2 Data is leveled using approach described above 3 Becau
38. Richard J Blakely Potential Theory in Gravity and Magnetic Applications Cambridge Univer sity Press 1995 414 p 8 Roest W R Verhoef J Pilkington M Magnetic interpretation using 3 D Analytic Signal Geophiscis vol 57 pp 116 125 1992 9 Salem A Ravat D Gamey T J Ushijima K Analytic Signal approach and its applicability in environmental magnetic investigations Applied Geophysics vol 49 pp 231 244 2002 10 Tchernychev M Snyder D 2007 Open source magnetic inversion programming framework and its practical applications Journal of Applied Geophysics 61 184193 11 Tchernychev M Johnston J Johnson R Empirical transverse gradiometer data processing method Quasi Analytic Signal approach AGU proceedings 2008 12 Tchernychev M Johnston J Johnson R Transverse total magnetic field gradiometer ma rine survey in Hawaii the Quasi Analytic Signal approach and multichannel total field dipole modeling SAGEEP proceedings 2009 240 Index 2D inversion 138 additional drawings clipping color names lines order points 32 polygons 33 annotations annotation types 195 color scale 197 label 196 Map annotation map scale 199 north arrow 198 polygon 200 stack annotation 201 text annotation 196 anomaly plots from worksheet in Google Earth balloons 191 autoscale clipping around profiles using triangulation 55 color scale compilation
39. The dialog is displayed on the screen All required parameters are separated in four groups 1 Main Earth s field parameters These can be taken automatically by computing IGRF model for data geographical location and time or entered by hand Latter also can be used if project does not utilize geographical coordinates 2 Data used for inversion a Data Three different selections available i All profiles All data in all profiles are used Unless window option below is checked this selection implies that unnecessary parts of the survey lines were cut the by user and only useful HVDC anomaly remains Program will use all data The results will be sorted along the polyline used for initial approximation ii Active profile The same as above but only one active profile is used 157 HVDC cable inversion DC Cable Total Field Inversion x M Use IGRF for Earth field rData for inversion Data an profiles Main field Declination deg 13 8514 Polyline name Line 1 X axis azimuth deg lao Y Use data window 2 m 200 Channel for inversion hr Main field Inclination deg Model Miscellaneous M Use sensor depth Cable type Pair of conductors i Use sensor atnuda Conductor separation 11 Y Smooth sensor depth w spline How to report depth From sea floor Smoothing parameter 1 00e 004 Model background Linear Iterations 2000 Initial XY seed Automatic Derivatives
40. as profile list If this box is checked MagPick will ask you to save the list of your profiles into a separate file For example load g 858g dat Check the box press Ok enter file name g 858g 1st Now exit MagPick and start it again Go to File Profiles Load list Select file g 858g 1st The result will be the same as with a simple load but we do not need to go through all the pevious steps again You also can create profile list file by hand using you favorite ASCII editor small shell script or your program Note that profile list file gives you more control on data loading For example 220 Tutorial MagPick can accept few data sets in one file but this feature can accessed only using profile lists 27 3 Putting things together map and profile data Goal MagPick is designed to work with two types of data map grid data and profile data Here we will be given profile data as initial information We will grid the data by MagPick Then we will load the created map into MagPick to see them together For a better understanding of the field structure we will present the profile data as a stack plot on top of the magnetic map Some optional learning material is included here to show how any geometrical information can be included in the view After completion of this part you should be familiar with the creation of magnetic maps using MagPick Files File g 858m dat is the only one we need here 1 Load profile data Start MagPick
41. at specific profile points There can be only two user marks at a time and their shape is different if you are working with global sign 4 or local sign A profile list If a polygon has been drawn on top of magnetic map you have two more choices e All inside polygon This means only profile parts inside polygon will be saved e Active inside polygon Only active profiles are will be saved and only the parts inside the polygon will be saved Figure 27 illustrates how this feature might be used to cut profile ends and produce new set of profiles 7 2 Profile data operations These operations are used to change profile data not their positions They include simple profile editing by cutting part of the profile and data smoothing with cubic spline Latter there can be used as low pass or high pass filters 62 Profile data transformations Figure 27 Profile cutting by saving an active inside the polygon Active profiles are red inactive profiles are blue Function All profiles in the window has been used While loading profiles back they become split by distance Cut from start of the line to the UP marker Cut part after UP marker to the end of the line direction of profile direction of profile Cut outside UP and DOWN markers Cut between UP and DOWN markers direction of profile direction of profile Figure 28 Different profile cutting modes 7 2 1 Cutting profile parts These operations are applied to t
42. be used for computation In most cases it is just sensors 1 and 2 3 Vertical middle channel This is the vertical channel number if three sensors are used This value is not used for Quasi Analytic signal computation 4 Gradient type specifies value to compute The choices are 97 Quasi Analytic Signal Operations Profiles Window Help ca e ae Interpolate grid gt Shift XY Smooth XY External smooth xY Drag profilefs Compute gradient Remove turns Remove short lines Auto Max Min pick Background Level using tie lines Accept Discard Figure 64 Analytic Signal menu e Magnitude of the horizontal gradient In this case program will not attempt to estimate vertical gradient it will just use the transverse gradient and history to compute amplitude of horizontal gradient component e Quasi Analytic signal This is primary case for transverse configurations only two sen sors are required The vertical component is estimated using potential field theory e Analytic Signal This is the case when third vertical sensor is available Program com putes true analytic signal no approximations are made 5 Vertical Separation meters This is two fold value e For Quasi Analytic signal it s additional upward continuation parameter It makes an estimate of the vertical gradient a bit smoother depending of the value The recommended value is the same as for ho
43. bin gnuplot exe G wx166Evc samplesimagpick v 2 3 gnuplot_hd gpl En Marine PNG z z0 B50 _Cancel Figure 140 Gnuplot output file creation dialog O Created 13 plot requests out of 13 targets Figure 141 Gnuplot completion message 195 Anomaly plots with gnuplot 01NOS y 0 1sasojo JUIOd eyep wo w aeoue sip OV 0 oz OL 0 OL 0z o Or 0 0S 0 00p 0 0Sp 0 00S 0 0SS oe n pi i 0009 Z oneyju s 2H ouueyo L onoyju s e L ouueyo N 21 H1d30 Y3LYM Sb 30N_LI1 VW HSI4 8 H1d30HSI3 09 ANI1 081 10 7 80 Z0 1 60 N 87 87098 leole LV1 M 91v8959 89 2S 1 NOT 8 E991 SSVIN v 1 Z 0 618c 9 S A 6 c0S909 X L dI 0 0S9 0 00Z 0 094 0 008 0 098 Lu pjay onoubeyy Figure 142 Sample plot created by gnuplot 196 Anomaly plots with gnuplot 24 4 Using Anomaly Plots in the Google Earth balloon annotations Using gnuplot software it is possible to include data graphs into annotations while exporting into Google Earth In this case Google Earth displays target information along with anomaly plot in the balloon when user clicks on the target See an example on figure Dipole ID 1 Longitude 157 58 365584 W Latitude 21 21 860481 N Depth 1 40m Mass 1663 75kg Amplitude 463 70nT Count 1 Fidelity goodness of fit 95 88 Model fit 5 25nT Angle w Earth s field 21 29 Dipole Inclination 17 58 Dipole
44. built in PDF conversion does not produce high quality graphics but Adobe Writer Add On for MS Word does 1 Google for pdftool epstool CutePDF to obtain these tools 185 Export and printing 5 After editing of the word processing document is complete create PDF version by printing to the appropriate driver You may adjust driver settings to reduce file size Look for JPEG compression and for DPI 300 DPI reduces file size dramatically However for quality paper lossless or no image compression is better because this does not smear color images created by MagPick View result with Adobe Reader Zoom on graphics to insure high quality 22 6 4 Converting PS file to high resolution bitmap Use the same menu as above File Convert Select tiff24nc device This produces uncompressed 24 bit color TIFF file which can be quite large You might want to convert this file later on into something compressed for instance PNG file Enter Resolution in DPI dots per inch You ming want to set higher resolution to get good printing quality however this can result in a huge bitmap Set the options how it is shown on figure 132 x Device Resolution Pages lt tiff24nc A Cancel Properties Help Variable Page Size y F Reverse Odd Pages Options dText lphaB its 4 dGraphicsAlphaBits 4 Figure 132 Converting PS file into high resolution bitmap e dTextAlphaBits 14 controls text anti alias
45. button Load in UTM setup For a good reference on UTM and other projections see 6 There are a lot of references on the Internet for example http www cnde iastate edu staff swormley gps gps html http everest hunter cuny edu mp Note for users in the Southern hemisphere by convention we should add 10 000 000 m to UTM northing for points located south from equator Magpick does not do it To do so you should reflect that addition in False northig 123 Potential field transformations 14 Earth s magnetic field model IGRF To estimate location and amplitude of the magnetic sources parameters of the main Earth s magnetic field see also figure 86 should be known International geomagnetic reference field normally provides these values It allows you to find the main magnetic field parameters for any point on the Earth between years 1900 and 2005 This model will be extended in future as new observations which are conducted all over the planet become available Enter date as decimal number gt Date decimal year Enter longtitude and latitude as Geodetical longtitude 9 0000000 lt 7 decimal numbers Geodetical latitude 53 0000000 41 Enter elevation in meters In many Elevation m f0 cases 0 is good enough i Attention Lon Lat in decimal degrees Press this button to calculate Calculate parameters of the Earth s main a magnetic field Inclination deg 67 90
46. calculation But in some cases program can not perform optimisation i e solve inversion problem Then this number can increase or oscillate Lin 4 97e 03 Ratio between minimum and maximum singular values for linear step of in version Small numbers about machine epsilon 1 e 7 show that a problem mathematically ill posed It can occur in case of large number of sources or their improper initial locations Non lin 2 42e 01 The same as above but for non linear step Has the same meaning lev 49729 32 Constant part of background function estimated on each iteration After calculation finishes the results appear on the screen and are stored into the special list If you have opened a worksheet window see below a new line is added to the worksheet All map windows are updated automatically o show horizontal coordinates of the found targets 16 2 Magnetic modelling based on profile data Magnetic modelling based on profile data is similar to the inversion based on maps but has some significant differences 1 The start of inversion is possible only from the Profile inversion all profiles in current win dow window Only activated profiles and subsets of profiles and therefore visible inside win dow are used for interpretation It could easily happen that many profiles cross a given win dow The interpreter should decide which profiles are suitable for inversion and select them To make this happen new item is added to th
47. comma separated value CSV format MagPick has ability to export them as GPX way points Most modern GPS hand held receivers support this format to download or upload GPS tracks routes and way points MagPick can convert target coordinates into a GPX file suitable for use by many GPS receivers This makes it easier for an end user to navigate directly to estimated target location Modern GPS receiver typically appears as mass storage device so GPX data can be copied into appropriate folder in the GPS memory and used by the GPS after it is disconnected from the com puter For instance Garmin Oregon 540t receiver appears as USB flash disk connected to the com puter so it s enough to move GPX file into Garmin GPX folder so the GPS receiver software can read these waypoints on next GPS start 188 Target position export Some GPS models utilize special USB or serial protocols to facilitate data transfer Open source software is available to connect to these devices Most useful is GPSBabel www gpsbabel org The user is encouraged to download and install this package because it allows MagPick to com municate with GPS device using these special protocols thus downloading target coordinates from spreadsheet directly into device File Edit View Window 4 Magnetic map picking gpx magpick 7 10 x Export worksheet file a AAA gO I 05 Ci temp targets le 15 5 Organize 24 Vi
48. compiled into MagPick code but some of its functions are still used via external utilities Polynomial profile and grid filtering is implemented Profile data leveling using tie lines is added Ability to compute IGRF values along profile Most important is the project workspace file added in May 2009 This brings program to the whole new level because it relives user from storing separately grid and profile data as well as remembering what was going on with the project 2 5 Version 3 20 2009 2011 Inversion part has been re developed using Open Source inversion toolkit 10 This inversion greatly simplified profile based dipole matching Ability to keep inversion protocols has been added The major milestone was implementation of the project file As most modern programs Mag Pick has now ability to save everything into project file which is in fact just a ZIP archive Improvements in the Transverse Gradiometer TVG data handling IGRF model has been included as built in part No need for external file igrf dat 14 Installation e Adding Google Earth export e Adding GPX way points export and load into external GPS device with GPSBabel software should be downloaded and installed independently e Adding ability to rotate coordinate system and export rotated GeoTiff e Additional function to load profile data using templates stock templates and created by the user e Implementing interface to PROJ library to
49. continued by calling the Operations Upward continuation menu If function is called for zoom window only data in zoom window is used not the whole grid The next dialog box appears on the screen see figure 83 15 2 Synthetic horizontal and vertical gradients As you saw above the potential field can be upward continued and therefore a vertical gradient also can be calculated Magpick allows you do to this operation as well as a calculation of horizontal gradients This option is available under Operations Gradients Here you can choose the type of gradient vertical horizontal or absolute value of horizontal gradient For a horizontal gradient you have to enter the direction positive clockwise from your Y axis 125 Potential field transformations Elevation positive up negative down 0 500 Z Require regularization Parameter 1 0000e 01 Elevation to continue field Positive up negative down For downward continuation regularization is needed Check this box and enter parameter You may need to try with different parameters File with continued field data misha projects magpick upward grd Z Upward continued file name Press button for browser File with original continued data misha projects magpick org up grd f JF Add files to the history list File with difference original minus continued field Will reperesent residual anomalies
50. coordinates along with current coordinate system information 6 Load Loads previously saved objects This way user can standardize his or her annotations Note however that objects are tired to the current UTM coordinates 7 Stick loaded to borders This option is very useful when you try to load annotations pre viously defined for other maps Using old and current coordinate systems programs tries to tie objects to the same places relatively to the borders as they use to be It is recommended however to have the same margin sizes as for the plot annotations were originally developed In fact menu options Add all frame annotations works exactly this way There is file in magpick distribution called frame txt located in the same folder as magpick exe When user selected Add all frame annotations MagPick tries to load this file with stick to borders option Result may require some moving by the user Each annotation has context menu Menu is displayed when annotation is selected and user right clicks inside selection handles Annotation context menu is shown on figure 147 Delete Move to Front Move to Back Figure 147 Annotations context menu 1 Edit calls annotation properties dialog This dialog is unique for each type see below 2 Delete removes annotation The same as Delete key 200 Map annotations 3 Move to Front Moves annotation in front of other annotations It can be useful if for instance user wants t
51. data can be decimated during reading To enable profile features you have to prepare a special file with file names and column numbers or use the Easy profile load feature The latter greatly simplifies access to profile information but has limited application for example each file can have only one data set if you need several data sets then you need to read the file two or more times What you use for profile loding depends on the format of your data and your expirience with a computer For example people with little expirience using Unix tools and with a task to process thousands of profile lines not unusual case with marine magnetic surveys may find it easier to write a simple script This would create a MagPick profile list file Users familiar with Microsoft Excel should assemble such a list manually Aslo all Unix tools are available under MS systems nowdays for free Probably one of the ways might be loading a few lines with Easy profile load and saving them as a profile list Such a list can be used then as a template This manual starts with a descpiption of the profile list file format hard part Users who want it fast can read Easy profile load Each line of the file consists of description of information loaded from one data file Description fields are separated with one or more spaces Here is the format of the line 1 It may contain or may not words SPLIT NN Here is SPLIT all capital letters key which indicates tha
52. data which are in the rectangle created by two mark positions and extension distance below applied to the left and right of the current line Thus if extension is 10 m and distance between markers is 50 m the program uses rectangle of 20x50m and everything in it is used Please refer to the map view for the distance to adjacent lines Inspect parallel profiles after inversion becaue they also will have synthetic field which should match observed 3 Circular Similar to above but circle is used to include additional data The diameter of the circle is the distance between profile markers Inspect adjacent lines if this type of constrain is used 4 Polygon Use polygon s on the map to constrain the data The polygon should be drawn by hand and have clipping property to be considered Inspect all lines included in the polygons after inversion is complete Extension distance This is the distance used to create rectangular constrain if it is selected Try off line locations It this value is O program puts initial location seed on the data line between the markers This could lead however to the poor convergence if target is actually sideways off line which is typical case Try off line location options enables automatic in versions with different XY seeds Assuming distance between markers is 50 m and off line location value is 20 program will try initial XY seed which 10 m left on the line and 10 m right The initial value which de
53. discuss MagPick workshe 99 142 Single magnetometer inversion Figure 92 Polygon on the map Here are most important values presented Note that positions can be formatted as full UTM or Lat Lon to be used to export into CSV file for Excel or other worksheet applications Depth is denoted as Z and it is positive downwards Because we used Depth from the sea floor option this is burial depth in meters Fit is RMS difference between observed and modeled field in nT Mass1 is an estimation for mass in kilograms Note that mass estimation is very approximate and may way by order of magnitude because magnetic properties of the target material are not known Angle is the angle between target magnetic moment and Earth s magnetic field degrees Discrepancy is the measure of similarity between model of observed data should be above 80 Amplitude is an amplitude of recorded anomaly in nT In this example two inversions are presented first with line 7 and second with lines 4 and 5 only Note that depth estimate is different even similar Standard deviations of the position are presented in the table as DX DY and DZ In this paricular example one can see that estimated position standard deviation is 0 5 m and depth standard deviation is 0 8 m Practically it means that object could be buried between 1 to 2 m Note that depth estimate only uses median water depth in the target area without taking into accou
54. distribution This is particularly useful when the data has spikes It allows you to see details better The gradient method gives you much more control on coloring but does not work with color equalization When you choose this option you can use the color scale editor to compose the best palette Show crosses If checked picks are shown as black lines with two small crosses at the ends Show profiles If profiles are loaded they are normally drawn above the magnetic field In some cases the can completely obscure the picture Check it off to avoid drawing This checkbox calls as well Profile plot parameters dialog which controls the stack plot 1f you need it see below Isolines If checked the contour plot is drawn on top of the magnetic map When you check it an additional dialog pops on the screen to specify plot parameters see below for details Snap to grid The program shows only positions of the centre of the cell where mouse pointer is default This way picking is limited only by centres of the nodes of the grid To avoid this check box off Grid color allows changing the coordinate mesh color Show X Y grid If checked the coordinate mesh will be drawn on top of the map Mesh steps This were intervals for coordinate meshes are entered Here is a description of the isolines contour plot parameters dialog box see figure 4 1 3 Fixed values Automatic To draw isolines you can choose pre defined level
55. disturb or even completely destroy the solution To avoid that linear function can be fit simultaneously with estimation of J T Ax By C or in the case of a profile based interpretation where Z values are important T x Ax By C Dz E2 There is total of 3 x M 3 or 3 x M 5 variables for the linear step which does not require iterations and can be solved at once To estimate position of the dipole the non linear problem has to be solved MagPick employs the simple Newton s method to estimate xo yo zo Given an initial guess and magnetization magnetic field can be calculated The discrepancy between observed and calculated field can be expanded into the Taylor s series truncated to the linear terms and written as the following equation gt oT g T OP 0 9020 E Bate 0 X0 Yo Z0 136 Implementation of inversion oT where x0 Y0 lt 0 9 X0 90 Z0 correction of the position and ate is the field calculated at the point of initial guess Then the new improved position can be found as is the matrix of partial derivatives of T at the point of the initial guess dd is the 71 79 6 The magnetization vector has to be estimated again using a new position The process has to be repeated till the discrepancy between the observed and calculated field becomes small and stable 17 3 Estimation of susceptibility and remanent magnetisation For mass estimation susceptibility and remanent magnetization of the body must be
56. downwards Induced magnetization 126 Potential field transformations is directed downwards too In this case b the main maximum of the field located right above the object Thus the horizontal location can be easily found Plate c shows the gravity field from the same object It is similar to field on the magnetic pole but does not have side minimums Theoretically when you apply reduction to the pole transformation all the specific maximum minimum shapes of the anomalies should change into simple ones However to do so you must know the direction inclination and declination of the object s magnetization which is generally unknown In some cases you can assume that objects have only induced magnetization and use the IGRF model to find it in this case the direction of magnetization coincides with direction of Earth s magnetic field Different objects also can have different directions of magnetization Because of this and other reasons do not expect that a transformed picture will be fairly simple Some anomalies could be transformed some not Reduction to the pole also might be an unstable operation on the equator see 7 for details Similar to the reduction to the pole the magnetic field can be reduced to the different direction of magnetic Earth s magnetic field and magnetization reduction to the pole just a special case of such a transformation In this case you should enter explicit directions of new field and magn
57. dummy grid you might find it useful to check out the Snap to grid option in the Settings dialog box MagPick can create dummy grid for you internally After you load profile information just create grid view with File New menu Program will show profile map faking underlying map internally There is no need for dummy file in this case 30 Basic operation of MagPick 5 1 1 Transforming equalized color palette into gradient One of the strong MagPick features is ability to produce rich colored maps using color equalization routine This feature was inspired by GMT system B However presently MagPick lacks color scale printing on the map There were requests to provide ability to export color scheme into other popular programs such as GMT and Golden Software Surfer for Windows This is now possible by transforming equalized palette into gradient and export latter one into CPT GMT B or CLR Surfer formats It should be noted here that Surfer at least at version 8 is not very robust in handling non linear color schemes A highly non linear palette with large number of color nodes can cause it to fail The following procedure is given to transform color equalized palette into a cpt or clr file After the grid of interest is loaded go to Settings dialog and press Change palette button The dialog with the following choices of Palette type is presented 1 Uniform This would let you select uniform palette a
58. export starts in SW corner and goes vertical first line starts in left bottom corner and is going North Second line starts in the North and is going South Line Decimation Depending of the slider value each column row of the grid can be exported or each other column row can be exported For instance if slider value is 4 only each 4th line is exported reducing amount of exported data by factor of 4 Sample decimation The same as above but relates to the sample rate along each exported line If 1 is selected every sample is exported If another value n is selected each n th sample is exported For instance if line decimation and sample decimation are both set to 4 amount of exported data is reduced by 4x4 16 times Coordinate decimals Number of decimal places in exported coordinates Please select this value to match your coordinates For instance for Latitude and Longitude in degrees the number should be 7 8 decimal places Data decimals The same as above but for the data For most of magnetic data 3 decimal places would suffice Export as Lat Lon inverse UTM Select this box to save data coordinates as Longitude and Latitude In this case inverse UTM projection is applied to each grid point coordinate pair prior to export It implies that original data was loaded as Lat Lon and UTM was applied during load Do not use this option for the data recorded in a local coordinate system 58 Grid operations e UTM setup A con
59. field nT Ok Cancel Figure 150 Color scale annotation dialog 1 Orientation Color scale can be oriented vertically or horizontally 2 Digits after dot Controls annotation format 3 Font size Size of the font used for annotation 4 Annotation Additional text used printed above the color scale Note that 1t should be short of color scale is oriented vertically 5 Level interval Annotation interval in data units Program tries to annotate in multiples of this value but not exactly in these intervals Because color scale is typically non linear some of the annotations can be omitted 6 Use custom levels If this option is selected user can type values to be annotated in the color scale one value per row 203 Map annotations 25 1 3 North Arrow C MagPick allows variety of north arrow types The option is available under Add north arrow context menu This adds default arrow to the map It can be modified as usual North arrow properties dialog is shown on figurg151 North arrow properties x North arrow type Simple v Simple Arrow direction Geographic North Azimuth lo IV Fill with solid color Fill color M Draw border aaa a Pen width lo Text color x Font size fo m gt 100 Ok Cancel Figure 151 North arrow properties dialog 1 North arrow type This value can be Simple to draw single large arrow in user def
60. file functionality To save your current MagPick workspace use File Projects Save or Save as menus Please select new or existing file with extension magpick If an existing file is selected its contents is overwritten however if zip archive includes files not used by MagPick they are not altered Most but not all workspace features such as window placements zoom level palettes etc are saved with the project The user cannot usually interrupt or cancel saving process To close the currently loaded project and remove all the currently open and minimized windows use File Projects Close Project menu This will remove all views and all data stored in the memory such a as profiles dipoles pipes manual targets etc To load a new project use File Projects Open and select existing MagPick project MAGPICK file If the file does not follow MagPick workspace conventions an error message is displayed and no data is loaded If file is a valid MagPick project file its content is loaded loading cannot be interrupted by the user Under MS Windows additional functionality is provided e If magpick extension is registered during program installation double click on the project file launches new copy of MagPick and loads project file e Drag and drop functionality is provided User can drag magpick file from the windows ex plorer into MagPick main window Program attempts to load the file after it is dropped into main windo
61. file requires manual file editing and a clear understanding of the list file format For these reasons Simple Profile Load function has been developed to facilitate data loading entirely via dialog box entries A step by step description of how Simple Profile Load works follows e Go to File Profiles Simple load Dialog box shown in Figure 14 appears on the screen e If you are using local coordinates only no Latitude and Longitude from GPS enter appropri ate False Easting and False Northing before picking any data files you also can use individual values for different data files You only need False Easting and False Northing if your coor dinates are expressed in large numbers such as UTM Note that the usage of false Northing 40 Basic operation of MagPick File already prepared for load gt Load X Data profiles x SPLIT 22 XFALSE 0 00 YFALSE 0 00 TIME1 Add Attention Set before adding data into list Delete Delete all Add channel iil V Save as profile list False Easting 10 00 False Northing fo 00 Note false Easting and Northing are to be added to your positions IV Filter by signal Signal column 2 Signal level f200 Ok Cancel E U Use signal values to reject the data gt Signal rejection level Data below this level is rejected If checked user is prompted to save configuration as a list Signal
62. for Corpse 27 Tutorial A aa Oi ce Sis o BERS ES a o Gade Gos Ee Se GR eG noS pete re epee ne We eae Se ee oe oe Sue eee eh ae ets ede as 27 5 Finding magnetic dipoles 2 20 00 ee ee 27 6 Finding magnetic pipes oo oe fee ee ee ee ER wR eR 217 1 Reduction to the Pole e us Gear drt cteg eet oh Bo Gh He ab He Shae He Ga SH A 28 Acknowledgments 29 Licenses and Trademarks 199 201 202 203 204 205 206 207 208 208 208 208 215 215 218 221 226 228 233 238 239 239 241 Copyrights 1 Copyrights 1 1 MagPick Copyright Notice Copyright C 1997 Mikhail Teherychev This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 3 of the License or at your option any later version This program is distributed in the hope that 1t will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along with this program If not see http www gnu org copyleft gpl html 1 2 PROJ lib Copyright Notice Copyright c 2000 Frank Warmerdam Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal
63. for the map inversion Change Positions file and Output file Press Start iterations wait till the discrepancy stabilizes and press cancel You can see a new location of the dipole on magnetic as cross x and number You can inspect the results with a workshee First worksheet column shows P if this is result of profile inversion The grid based inversion is shown with G On the profile inversion view you can the see result of calculations as dashed lines See figure 163 50000 50000 49800 49600 49400 49800 49600 49400 49200 49000 48800 49200 49000 48800 T nT 48600 48400 48600 48400 48200 48200 48000 L 48000 6 7 8 9 10 11 12 13 14 observed synthetic Figure 163 Inversion of profile data Now we can work with the profile inversion as we did it with the map inversion Note that nothing prohibits as from applying the map inversion The results come to the same worksheet but it has G in first column Set the initial position depth in the different places of the map 232 Tutorial and try to invert the data by profile inversion You may note that MagPick reports depth about 0 6m Take a guess why Hint what was the separation between top and bottom sensor You can note as well that when you set initial depth to less than 0 6 the process does not converge This is because it s less thanthe real depth of the object It is recommended to start with the
64. go to Options Drawings and press button Add Choose file the type Clip Pick the file you have just created Press Ok and press Ok once more to close the dialog e To reflect clip redraw the picture Edit Redraw Please note that Additional drawings list is not saved when you exit MagPick Therefore you should load the clip file again when you start MagPick next time 54 Grid operations Y km Y km siria 1 200 Jenne neee 1100 100 200 300 400 100 200 300 400 X km X km Figure 23 Result of grid clipping Draw polygon then go to Operations Clip grid 6 4 Clip the grid Clipping the grid does not create an additional file If you are doing clipping in the zoom window the area you see in this window is affected Therefore you must save the grid file if you want to use 1t in the future The following is the procedure to do a real grid clipping Operations is next e Go to Edit Polygon The mouse changes its shape to the pen Draw a polygon the left button adds a node to the polygon the right button removes latest node To close the polygon click on 1ts first point To draw a new polygon go to Edit Polygon one more time existing polygon will be erased e Goto Operations Clip grid Choose the part you want to be blank inside or outside polygon Press OK e The program clips the grid in the current window and in the all windows which share the same data array MagPick red
65. in place of gnuplot executable Gnuplot header file This is part of MagPick distribution which describes how plots are to be created It is gnuplot text file which can be edited by hand to alter colors line widths etc File is located in the same folder as the program magpick exe User can copy it from there and edit to change appearance of the plots changing path to the file accordingly Plot output folder Place where output files are created It is suggested to have empty folder because program creates one file per plot Type Marine or Land The difference is in the header For marine type fish depth altitude is reported Output format Available selections are PNG PDF Postscript JPEG SVG Xfig DXF These formats are supported by Gnuplot no MagPick Default is PNG Canvas size Size of the bitmap file in pixels This only takes effect for image files not for vector files such as PDF After Ok button is pressed program creates special task file for gnuplot and calls it with the header required format and canvas size Gnuplot starts reading protocol files and creating output graphic files in the designated folder Progress indicator is displayed based on time going from 0 to 100 and then again depending on how long it would take User can cancel at any time with some files possibly created If Gnuplot encounters errors for instance because of errors in user supplied header file these are displayed in th
66. in the data and assigns new lines if gap is longer than split distance 3 Keep original line names with numbers If this option is selected each new segment of the T11 Profile data transformations EAS Redraw Select Pan map Simple pick Rectangular pick Delete pick Zoom Delete Direction Pick profile i i Set marker 6750 6800 6850 Find marker New Ad color scale Add annotation Add polygon Add polyline Add map scale Add stack scale Add north arrow Add all Frame annotations Edit All Figure 38 Menu for polygon drawing Polygon properties x Horizontal Fill color Border color Border width 2 Y Use polygon to clip data Area 82890 376 Ok Cancel Figure 39 Make sure Use polygon to clip data is checked existing line is assigned a name in the format line number where line is original line name and number is sequential number of the segment For instance if original line 1 was split into 3 sections new lines with names 1_1 1 2 and 1 3 would appear Note that split operation can be applied multiple times in this case original line name is still kept For instance assume after 78 Profile data transformations Profile Browser Loaded profiles Alle Martinhal_201210_03 Survey INTERPOLATOR INT Alle Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinh
67. includes position shift along and perpendicular to the track Dragging recalculations can be used for repositioning It is simple simulation of the object being towed behind the vessel There are some note worthy facts about the way profile data is handled in MagPick e All data is stored as floating numbers 4 bytes This may lead to loss of accuracy if you are operating with large numbers Typical examples are full UTM coordinates or a full magnetic field while looking for anomalies less then 0 05 nT In the magnetic field this is negligible but you could note difference after saving data with MagPick It is not recommended to use full UTM use false northing and easting to reduce the accuracy requirement There are two profile views in MagPick One is simple Profile view where you can see one profile at a time This kind of view operates with the common profile list Therefore changes of this view could be seen on each other view If you do All profiles in the window from the map view Profile inversion in older magpick versions MagPick duplicates all profiles which are inside current map view Note that only one All profiles in the window can be opened at a time for one map view When you close this window the data is not copied back into the main profile list Therefore you should save profiles before closing this window if you did modify them MagPick will usually warn you about it 61 Profile data transformations e Profile oper
68. internal there is no view which shows T n most similar is view T distance but this is not the same T n gets approximated with a cubic smoothing spline with the smoothing param eter Large parameter values provide an interpolating spline typical values like 1 10 100 or more while small values typically 107 or less give a smoothed curve The latter is of interest because it works as a low pass filter MagPick provides a view of both original and the smoothed curve a typical result of a smoothing is shown on figure 32 As soon as the user is satisfied with the result he should commit changes and replace the original values with smoothed ones There are two choices the original curve gets replaced with a smoothed one which is an equivalent to low pass filter or the original curve is replaced with the difference of the original curve minus the smoothed one thus providing high pass filter Smoothing also can be applied to the part of the curve between marks In this case the value of the smoothing parameter is specified by the user It is related to the middle of the interval The ends of the interval have high smoothing values which essentially give an interpolating spline then parameter decreases by the Gaussian law to the middle of the interval Therefore the middle gets smoothed ends stay similar to original values thus discontinuity at the ends is not introduced One typical smoothing usage is stressing of the high frequency comp
69. interpolate grid data go to Profiles Interpolate and pick an interpolation method A new map window created automatically during interpolation see refmakeagrid 5 5 3 Loading profile data using templates The third profile option available is profile load using template This option combines the flexibility of list load and simple load and is very useful when a significant number of files need to be loaded It is assumed that all files have the same internal structure which matches one of the stock templates or to a template created by the user To create a template the user can load one of their data files using simple load then save list file and then convert that list file into template Templates can be stored as part of the MagPick installation and used to load additional data files The option is available from Files Profiles Load with template menu figure 15 After selecting Load with template the file selection dialog opens It is important to know that multiple files can be selected here Under Windows hold Shift or Ctrl keys to select multiple files Under Linux simply click on file names All selected files must have the same internal structure 43 Basic operation of MagPick _ _ _ ____ 4 Magnetic map picking File Edit Inverse Options Operations New Open Save Export XYZ Projects Load list Simple load Ta Load with template Save pic
70. into State Plane California zone 2 US survey foot The sequence of operations is the following 1 Go to Options UTM setup and click on Use other projections button 2 Enable Use proj Click on Match UTM to automatically fill to field as proj tmerc lat_0 0 lon_0 123 k_0 0 999600 x_0 500000 ellps WGS84 datum WGS84 It also fills in false Northing and Easting 3 Enter from field by typing init epsg 2226 Press Ok to close the dialog and then Ok to close root UTM dialog It completes interesting transformation whatever is called Lat Lon in the program is actually California zone 2 State Plane For instance if you set mouse cursor status to show Lat Lon it shows State Plane in feet instead 4 Now save profile information by selecting File Profiles Save and checking Save as Lat Lon box You can also reduce number of decimal places in XY because there no need to keep extra digits after dot 5 New data file has its coordinates in State Plane header still might say Longitude Latitude 12 6 8 Example advanced Load from State Plane process in UTM save in WGS84 Lat Lon In this example it is assumed that initial data file has its position in California State Plane zone 2 NAD 27 The task is to load these data in MagPick re projecting on the fly into UTM zone 10 WGS84 do data processing such as export GeoTIFF in UTM 10 WGS84 and then save data or target positions etc as longitude and latitude in WGS84 1
71. into part of the map Note that when you do picks they appear in all widows which represent the same magnetic map Certainly you can save and use this information 2 More advanced Rectangular pick The action we just have taken with a simple pick has a problem We used our eyes to find where maximum and minimum were located MagPick can do it for you so you do not have to stare at screen This is the procedure e Go to Edit Rectangular pick The cursor changes its shape Now go to point 6 12 Look at the bottom of the main window to read coordinates Note that it says First Press left 226 Tutorial button and drag the mouse down and left up to point 10 8 Release mouse You have just showed MagPick the area to search for maximum field e Move the mouse and look at the status line It now says Second This means you have to show MagPick the second area where the minimum is located Go to point 6 14 and repeat the operation drag to point 10 10 As soon as you have released the mouse button MagPick connects the maximum point in the first area and the minimum point in the second You may note that this pick differs from what you did by hand e Important You must show the maximum area first and minimum second Areas can over lap 3 Removing the pick Consider we did a pick by mistake and we want to get rid of it Go to Edit Delete pick then move mouse to the middle of the pick you want do delete click the left button It
72. list of inversion parameters Nie Ss Depth Figure 86 Coordinate system e Main field inclination Inclination of Earth s magnetic field in the geographical system angle I of figure 86 e Main field declination Declination of Earth s magnetic field in the geographical system angle D of figure 86 Positive to the East e Azimuth of X axis Azimuth of you local X axis angle A of figure 86 In case your local X coincide with geographical east A 90 Positive to the East 129 Estimation of magnetic sources Total magnetic field Magnitude of T on figure 86 Susceptibility cgs Susceptibility per volume This value can be used for mass estimation It is supposed to be known Remanent gauss Remanent magnetisation per volume Used for mass estimation Elevation For grid inversion all data points should have the same Z coordinate You can in troduce this value here Note that you should then set initial depth of dipoles correctly Z axis goes down Margin space If you wish you can use only part of the window in the estimation by setting appropriate margin Number of iterations The limit for the iterations program to perform inversion Estimation is stopped after the iteration counter exceeds this value Limit to stop After each iteration MagPick calculates the discrepancy between observed and synthetic field If there is a difference in these values taken on two sequential iterations less the
73. magne tometer fish being dragged behind It is clear that the magnetometer position is not the same as GPS antenna position The distance between antenna and tow winch and tow cable length must be taken into account to find the real sensor position This problem is complicated and may have different solutions based on the price paid the system including usage of acoustic underwater positioning systems gyro compass on board or complex cable dynamics calculations Magpick provides two the simplest ones 1 a simple shift along the recorded GPS track 2 using simple approximation of tow system with dragging technique Neither method takes into account possible difference between ship heading based on position information and the real ship heading which can be obtained with gyro or magnetic compass 13 Profile data transformations Both methods are available under Profiles Drag profiles s in map grid view The profile data should be loaded There is no option between marks The transformation is applied to the entire line of data or to all lines To proceed with transformation perform the following e After profile data is loaded and map grid view created go to Profiles Drag profile s Choose the item you want to drag It can be or All profiles or Active profile Specify shifting method It can be Drag profile or Shift along profile In the first case the program uses the dragging method in second case it simply moves the dat
74. magnetized sphere of unit mass has the following simplest form 1 y x0 y yo 2 20 Here xo yo Zo are coordinates of the center of the sphere and x y z are coordinates of the obser vation point If the sphere has a magnetic moment with components Jx Jy J magnetic field can be expressed as X Vads Viydy Vizdz Z Vedy Vedy Verd where V denotes the partial derivatives of potential X Y Z are horizontal and vertical compo nents of the magnetic field In case of full vector measurements these values have to be projected on direction of the Earth s magnetic field Considering D declination of the Earth s field and J inclination formula for full field can be written as T XcoslcosD Ycos sinD ZsinI Note that vector J can has an arbitrary direction and value Thus to solve the forward task in the general case three geometrical and three amplitude parameters should be known for each dipole The magnetic moment can be considered as a sum of induced and remanent magnetization In this case we know these values per volume J can be expressed as J VKF earth JE JremVH rem 10 K magnetic susceptibility per volume cgs units F magnitude of Earth s magnetic field nT Nearth Unit vector in parallel to the Earth field 135 Implementation of inversion J rem remanent magnetisation of the sphere gauss Tirem Unit vector parallel to direction of remanent magnetisation v
75. magpick_xt which is executable version of the program 3 3 MS Windows installation If you have the magpick exe file the only problem you may have is with ctl3d32 dll library At least two versions for Win95 and NT exist You will need to find the right one for your platform The next step is copying of this file into a windows system directory probably C WINNT SYSTEM32 under NT and C WINDOWS SYSTEM for 95 98 like systems Please note this file can not reside in the same place as magpick exe After files are in place everything should run Later versions of magpick also have a setup program based on Install Shield 5 0 free edition 4 MagPick project files Starting with version 3 00 MagPick provides ability to save the current workspace into a single project file This project file is represented by a ZIP archive with multiple files within The ZIP file itself has custom extension magpick ZIP functionality is added to the program as described below 16 MagPick project files e For MS Windows version static library version of Info ZIP zip and unzip utilities were com piled and linked with the rest of MagPick code These utilities slightly differ from the original versions of Info ZIP to ensure static linking The Info ZIP license is included with MagPick distribution e For Linux version external Info Zip programs zip and unzip are used Those should be in stalled by the user prior to attempting to use MagPick project
76. not modify or use for other purposes SZIP implements an extended Rice adaptive lossless compression algorithm for sample data The primary algorithm was developed by R F Rice at Jet Propulsion Laboratory SZIP embodies certain inventions patented by the National Aeronautics amp Space Administration United States Patent Nos 5 448 642 5 687 255 and 5 822 457 have been licensed to ICs LLC for distribution with the HDF data storage and retrieval file format and software library products All rights reserved Revocable in the event of breach by the user or if required by law royalty free nonexclusive sublicense to use SZIP decompression software routines and underlying patents is hereby granted by ICs LLC to all users of and in conjunction with HDF data storage and retrieval file format and software library products Revocable in the event of breach by the user or if required by law royalty free nonexclusive sublicense to use SZIP compression software routines and underlying patents for non commercial scientific use only is hereby granted by ICs LLC to users of and in conjunction with HDF data storage and retrieval file format and software library products Copyrights For commercial use license to SZIP compression software routines and underlying patents please contact ICs LLC at Address ICs LLC 2040 Warren Wagon Road P O Box 2236 McCall ID 83638 Phone 208 315 2877 Fax 208 634 7720 Email support ics4chip
77. one see below Dn nF ug N attempt to estimate mass root two see below 7 accuracy of the fitting of the total magnetization during mass estimation 8 X coordinate of low left corner of the window where inversion has been made 9 Y coordinate of low left corner of the window where inversion has been made 10 X coordinate of upper right corner of the window where inversion has been made 11 Y coordinate of upper right corner of the window where inversion has been made 133 Estimation of magnetic sources 12 Inclination of the total magnetization vector in the geographical system degree 13 Declination of the total magnetization vector in the geographical system degree positive to the east 14 Magnitude of total magnetization possibly divided by scaling factor 15 X component of magnetization vector in the local system cgs units 16 Y component of magnetization vector in the local system cgs units 17 Z component of magnetization vector in the local system cgs units Some simple operations are available in the work sheet All of them can be reached by window menu or popup menu right mouse button Here they are Load Load file content into the work sheet Previous content will be lost e Save Save work sheet content into the file You are encouraged to do it periodically during the session e Delete Delete current row normally highlighted but not necessary Program re numerates all
78. only UTM When the survey consists of multiple areas it is advisable to use the same short projection for all of them This can be achieved by selecting projection once along with its false northing and easting and saving projection parameters into the file with extension utm This file should be loaded each time a new portion of data or new survey area is loaded Figure 71 shows typical layout in case of multiple survey areas It is assumed that areas are not too far from each other tens of kilometers Using common projection parameters allows to keep short projection coordinates consistent between the areas this is useful even if they are not loaded This also may include datum transformation starting with MagPick version 3 20 107 Geographic projection transformations UTM and PROJ 4 E 2 S 3 S E a Area 2 16 Area 1 Xfalse Y false 0 0 Short Easting Figure 71 Selecting projection parameters in case of multiple survey areas into MagPick at the same time Using its own false Easting and Northing for each of the areas is error prone because coordinates could be confused between areas Direction to the Geographical North is shown to remind user that in general projection North also called grid North does not coincide with the direction to the Geographical North 12 3 Locally rotated coordinate system In certain cases it could be beneficial to rotate coordinate system
79. proj uses different con vention for rotation 12 6 6 Example Gauss Kruger zone 9 Pulkovo 42 North Caspian Sea with 7 parameters Input data ordinary GPS in WGS84 from statement proj latlong datum WGS84 Output data Gauss Kruger Pulkovo 1942 EPSG code 28409 meters to statement init epsg 28409 towgs84 43 82 108 842 119 585 1 455 0 761 0 737 0 548 Note that EPSG code definition here does not include datum to datum transformation WGS84 to Pulkovo 1942 therefore transformation parameters must be added to the to string Control point 50E 45N Easting 9421246 81 Northing 4985511 01 meters Note This is the case when datum transformation not included is EPSG specification and therefore needs to be specified with towgs84 parameter with no spaces between values By convention 9 is added in front of Easting to reflect Gauss Kruger zone number In the above example if inversion results are saved as Full UTM they are in Pulkovo 1942 Gauss Kruger zone 9 if they are saved as Lat Lon they are in WGS84 To save them as Lat Lon in Pulkovo 1942 load the data and then replace from as proj latlong omit datum 119 Geographic projection transformations UTM and PROJ 12 6 7 Example advanced from built in UTM to State Plane In this example it is assumed that data has been originally loaded using built in UTM and Simple load option The data was recorded in San Francisco Bay and user wants to convert them
80. projection to 114 Geographic projection transformations UTM and PROJ save the data Match UTM button expands built in parameters into to string For instance for UTM with central meridian 123W WGS84 the string is expanded as be proj tmerc lat_0 0 lon_0 123 k_0 0 999600 x_0 500000 ellps WGS84 datum WGS84 Note that this 1s complete Transverse Mercator specification 2 Rotation button enables function to rotate coordinate system It works the same way as in case of built in UTM except that points X1 Y1 and X2 Y2 are to be specified in the to system Note that false Northing and Easting are set to zero for rotated projects 3 Expand button provides expanded information about selected projections using PROJ syntax It pops up information window and shows all projection parameters It is most useful for ex panding EPSG codes and checking if they provide datum transformation parameters Use What to expand selection to select from from to to For instance for EPSG 2801 full expanded projection looks like the following Expanded Projection x What to expand to v tinit epsg 2801 proj lcc lat_1 30 7 Hat_2 29 3 lat_0 28 5 lon_0 91 33333333333333 x_0 1000000 y_0 0 ellps GRS80 units m no_defs Figure 78 Expanded projection parameters Here complete projection string is init epsg 2801 proj lcc lat_1 30 7 lat_2 29 3 lat_0 28 5 lon_0 91 33333333333333 x_0 1000000 y_0 0 ellps GRS80 un
81. recorded with GPS locations or transformed into latitude longitude positions A UTM meters transformation is applied upon loading the data into MagPick and then Google Earth requires a reverse UTM transformation back into latitude longitude for geo referenced export An example of the Google Earth export is shown on figure 118 e Image US Geological Survey f rr y a y j 0 2010 Google Fa s a Google Imagery Date Feb 28 2006 29 36 305 N 82 48 230 W elev 16m Eye alt 293 m Figure 118 The MagPick map is overlays the satellite imagery available from Google Earth n the simplest case MagPick exports a georeferenced Window s bitmap and then launches Google Earth 1t must be installed on the computer prior to export The user sees the same information in the Google map as was displayed in the MagPick map Other more detailed export features include the option to create a semi transparent bitmap or make one color preferably white fully transparent Other options include export of interactive vector elements like profile locations target and dipole positions and information and user surround drawings etc The export is available from the map window under File Picture Export Google Earth menu shown on figure 119 170 Export and printing Magnetic map picking s3 s5 w inversion File Edit Inverse Options Operatio New Save Export XYZ Projects gt Profiles Open pick Save pi
82. scale now Make sure Induced only and Linear only are unchecked Set Grid type as GS ASCII grd This is a well known Surfer ASCII grid format Now change file names Set Position file to be position dat Calculated grid this is where synthetic field from the source is written to be calc grd and Difference ob served field minus calculated diff grd Set Object type as Dipole s You are done here Press Start iterations e You will see a small progress window with Iteration number and Discrepancy Discrep ancy value is decreasing When it stops decreasing for these data it is about 3 6 press cancel You have just found the magnetic source MagPick shows the horizontal position of your dipole as sign with a number To see it better zoom to the central part of the map and turn off the color map You can see that it was not placed not on the middle of the pick but close e There is another form of data representation called the worksheet Go to Inverse Work sheet Dipoles You will now se a table with one row which represents the location of the source you have just found Inspect the synthetic field Create a new empty grid view and load file calc grd This file was created during calculation You may need turn on the color map for that view Compare the observed and calculated fields Inspect the difference observed minus the calculated If the case is a good fit it look like random picture Again create a new veiw and load fil
83. screen show the process View results As soon as a calculation is completed you have two choices go to the Files Recent files and pick you file if you checkedAdd files to the history list or simply open a new window and load the calculated file Examine the result of calculation in a new window Exercises Try to recalculate this field with different directions of the magnetic field and magne tization To do so uncheck Use reduction to the pole button and enter for example new declinations and inclinations as zero case of magnetic equator and see what you get 28 Acknowledgments I thank everyone who participated in this project by using or testing MagPick My many thanks to Dr Jannis Makris and Rainer Kasig from the University of Hamburg who has inspired this program My special thank you to Dr Dennis Wilkison and George Tait of Geometrics who sacrificed their spare time checking and editing this manual Without their effort this software would never been released to the public 29 Licenses and Trademarks The following third party software packages are used in MagPick 1 2 wxWindows version 1 68 library under wx Windows license Generic Mapping Tools GMT http gmt soest hawaii edu by by Paul Wessel and Walter H F Smith University of Hawaii under GNU General Public License NetCDF Network Common Data Form library http www unidata ucar edu software netcd by UniData LibTIFF library http
84. setup be applied before export If checked inverse UTM will want this feature Check UTM parameters if you you wish to export min max or middle Select here which elements of the pick point or all of them Select format decimals degrees and minutes or degrees minutes and seconds Choose number of digits after dot Press this button to see if inverse UTM transformation and scaling are set Note check it anyway AS E Inverse UTM on output UTM parameters Linear scaling on output X scale 1 000000 X offset 0 000000 Y scale 1 000000 Y offset 0 000000 calls this dialog Export type Segments Linear scaling will be used if this box is checked It takes effect after UTM transformation Cancel Includes segments points or both Hingar transformation parameters scale and offset E of export DXF and BNA only Figure 12 Export picks as DAT file Export results can be loaded into MagPick if you export them as Magpick points or Magpick lines These represent the internal MagPick format for additional drawings on top of a magnetic map In the first case middle of the picks gets exported in the second case picks as lines You can choose the color and size of annotation for these elements 5 4 Automatic pick Besides manual anomaly selection MagPick has a tool for automatic finding
85. the map This way you can virtually present any vector information on top of the magnetic map Key word UTM stands for UTM projection This means that coordinates in the file are expressed in UTM Other keyword is GEO which means that position are represented by longitude and latitude Because MagPick normally operates with short form of UTM projection proper UTM 225 Tutorial parameters should be set to allow program conversion from longitude and latitude to Northing and Easting See the full manual for complete set of features and format description 27 4 Detecting of magnetic bodies Goal MagPick was no originally designed as a visualization tool but rather as an instrument for locating of magnetized objects This tutorial shows how you can use MagPick as alocating tool do it This introduction section is very simple it explains why MagPick is called MagPick Files As an example we will use the magnetic field of a real bomb from World War II GP 500 ISS UK General Purpose 500 Libs excavated out of Kuhwerder hafen Hamburg Germany in September 1997 Its mass is 226 5 kilograms the field was measured with G 858 magnetometer two sensors top and bottom on grid 17 x 20meters Susceptibility was estimated as 0 87 cgs and remnant magnetization as 0 24 gauss we will not discuss here how it was done see rest of the manual for that Files we need are located in subdirectory bomb 1 Simple pick of magnetic o
86. the paper Output MagPick has three output modes e Printer this sends PS file directly to the printer In fact this option is never used e File allows user to select file to save PS file This is used when user is certain about picture appearance e Preview most commonly used option When selected Magpick completes PS output into temporary file and then starts external program typically GSView to show the file Using GS View controls user can convert PS file into PDF high resolution TIFF or just print it Fit paper size This option makes Magpick to fit plot size to paper size regardless of scale Resulting picture will fit on the page but most likely have odd scale X magin Y margin Margins in paper size to fit picture on the page Printer command Command to send PS file to the printer It s used under Linux Preview command Name of the program to be called when Preview option above is selected For MS Windows environment the recommended program is GS View Include full path here After PS output is complete Magppick starts this program to view the result Note that Mag pick interface is not blocked when program starts However temporary PS file is removed when Magpick exits and therefore GS View loses its picture Complete all necessary GS View opretaions before closing Magpick Titles Duplicates Magpick Titles dialog With introduction of floating annotations this option is mostly obsolete It allow
87. the project This Figure 1 Error messages shows that MagPick cannot use temporary folder Possible workaround is to define environment variable MAGPICK_TEMP_ FOLDER Here is how it can be done under Windows 7 or Vista 1 Use Windows Explorer or other program to create an empty folder with full access for the user For instance create C magpicktemp folder Go to menus Control Panel applet and press system Click on Advanced system settings link and then on Advanced tab In this tab press Envi ronment variables button Use upper part of the dialog to define new user variable by pressing New button Enter new variable as shown on the example 2 Answer Ok and close all dialogs sequentially Exit MagPick it it running Start magpick again Hopefully it fixes the problem User also could disable erasing of temporary files by setting RemoveTempFiles 0 in Mag Pick INI file 19 Basic operation of MagPick Edit User Variable x Variable name MAGPICK_TEMP_FOLDER Variable value C Imagpicktemp cme Figure 2 Error messages shows that MagPick cannot use temporary folder 5 Basic MagPick operation Here is some basic ideas behind MagPick MagPick works with information that can be presented as a grid files in SURFER ASCII BIN and NetCDF format and with information presented as set of profiles simple ASCII files with space tab separated The grid information is compulsory it p
88. to use a base station in offshore surveys where there is no place to setup the sensor at all One of the substitute methods is using the tie lines survey lines crossing other lines in the perpendicular direction Ideally the field at the line intersections should be the same if not these discrepancies can be used to level the data In certain cases this method greatly improves overall magnetic map thus removing certain distortions MagPick offers some solution to this problem which is not universal It uses the following simplified approach to level data using tie lines 1 Program searches for all profile intersections and computes field differences at each intersec tion as well as intersection position 2 It is assumed that there is linear background function for each profile This can be function of time if time is recorded or function of fiducial number sample number This is only true if recording time was short enough so magnetic time variation can be considered linear If these conditions are met the goal is to estimate bias and rate for each profile to minimize discrepancies at the intersections Therefore 2 x N variables have to be estimated 3 There should be sufficient number of intersections to estimate unknown rate and bias for each line First of all each line should have at least two intersections with other lines Then total 88 Leveling tie lines Accept smooth results x What to accpept All
89. to Common parameters and press Change palette Choose Uni form set palette number you like see how the picture changes after you pressed Ok in Com mon parameters dialog Mapping of data into color is linear if Equalize colors box is unchecked and non linear based on your data distribution if Equalize colors box is checked This last method provides a col oring where each color occupies the same area on the screen as any other color Therefore the picture is much richer Try for example with palette 34 Use with color equalization and without See the difference A second method gradient palette gives you more control on the color you wish to have It does not provide color equalization Go to Change palette Gradient You are seeing the gradient palette with control points You are free to move these points change their colors and values with a mouse Press the right mouse button to see a menu There is a pre defined set of palettes for your convenience For example choose Land and Sea and then choose Revert colors The gray is large To reduce it move the second from the top color point up You can move other points as well to provide the same interval for each color Press Ok now and see what happens Advanced mapping techniques The mapping methods include shaded relief and illuminated color map The last may as good for magnetic data than for topography It takes a considerable time to calculate and plot the picture Let s star
90. to feel a difference e Average data depth This value is for information only Program calculates the average elevation of all the data points to get an idea about the possible initial source depth specified by the interpreter Initial depth should be bigger than the average depth It is possible that in the case of improper initial depth during iterations the program can move sources above the observation level Change the initial depth and repeat calculation in that case e Induced only Linear solution only not implemented for profile inversion e Output file Instead of creating calculated and observed grids the program writes an ASCII file file with that information It stores the calculated field inside the profile structure This means you are seeing the calculated field immediately after calculation This information disappears if you repeat calculation or close profile inversion window During the calculation itself the program posts on the screen the same messages as in the case of a grid based inversion Unix version After the program finishes it creates an ASCII file with the following structure 132 Estimation of magnetic sources e Line sign F space and name of the file e For all datasets activated in this file trough two empty lines six columns of numbers X coordinate Y coordinate Original Z coordinate Smoothed Z coordinate Original magnetic field Nn Bo NY Calculated magnet
91. top of a magnetic map See Drawing and clipping on top of the map All these are available under Files Export pick menu During the export to DAT BNA and DXF pick positions can be trans formed two ways e Linear transformation along X Y axis can be applied This includes scaling and offset Inverse UTM transformation can be applied see Universal Transverse Mercator Gauss Kruger in MagPick This result can be presented in geodetical latitude and longitude while MagPick works with Northing and Easting Figure shows sequence of dialog boxes for exporting dat files It is important to check if the UTM transformation is used it may be not what you want to keep old and exported data in the same coordinate system Option Degrees and minutes and Degrees min and sec makes sense only if your data was loaded in MagPick using Lat Lon not recommended or you do inverse UTM transformation on the output In addition to UTM transform you can apply a simple linear scaling and shift Exporting DXF and BNA formats are similar except you have less choice in what you can export You can export end or middle points or picks as line segments or both Please note that the results of a DAT DXF and BNA export are not loadable back to Magpick 36 Basic operation of MagPick Export fields rA mum X minimum Y minimum Z minimum X middle Y middle Z middle Format Decimals Positions after dot 8 Transformations
92. top of the map was added The profile graph view was was developed The observed magnetic field can be viewed as set of linear graphs such as T x T y T 1 and T p Here T field x y planar coordinates of observed points distance along profile p projection of the profile on given line Inversion based on profile data was implemented This means that all or part of profiles cross ing a given window can be used to estimate the position of the magnetic source Calculated and observed curves are plotted to see the quality of the solution Point marking on graph map profile view was added The mark on the profile automatically appears on the map view and vise versa Thus the space location of interesting points can be easily found Printing previewing on postscript printer was implemented MagPick was then used to process data of Hamburg harbor area which was collected during summer autumn of 1997 Some places were examined by divers in most of the cases the magnetic source was found around 30cm in the plane from the predicted point Thus MagPick was proven to be a good tool for magnetic interpretation Version 2 0 1998 1999 During this period MagPick was not used extensively The most significant use was designing a pipe inversion This was requested by Geometrics in spring 1998 This kind of magnetic source is more difficult for interpretation than magnetic dipole It appeared that pipe locating is far more ambiguou
93. try it few times to find the best setting 28 Basic operation of MagPick 4 Possible picture modes 4 Icon shows your current light No color map parameters Simple color map Shaded relief black and white Color illuminated map Drawing mode Color illuminated map E 2 Parameters for Shaded relief and color illuminated maps 43 Light azimuth from north and Light elevation degrees light elevation in degrees 38 Light azimuth degrees Data scale 1 00000 3 Data scale for Shaded relief and color illumination Data multiplied by this value before k Ok _cancel shade is calculated You may need to try different ones to find the best Figure 9 Map drawing mode dialog MagPick supports two coloring schemes uniform palette and gradient palette In the first case the palette is defined by all its colors Total number of colors can not exceed 255 There are a set of built in palettes which are available in Magpick In the second case the palette is based on a relative small number of color nodes each with its own color and data value Color for the intermediate data values are interpolated Gradient palettes can be saved or loaded from a file and some set of build in gradient palettes are available as well Ufiform pallete dialog box Grdient color dialog You can choose from number of pre defined color palettes by moving this slider
94. use ft Time variable Fiducial Solution type Speed up distance meters 20 Least Squares L2 T Show results as Replace original field Preview color Ok Cancel SPRING GREEN Figure 56 Profile data leveling dialog 5 Show results as This field has selections Preview as smoothed and Replace original field In the first case data is shown as smoothing results in the profile window s User should inspect them and accept or discard In the second case leveled results simply replace original profile data In both cases profile data needs to be saved if user plans to use them in the future 6 Preview color If option Preview as smoothed is selected this field controls color name used for preview in the profile view window After OK button is pressed program estimates number of profile intersections If there is sufficient number of intersections found the warning messagd57 is displayed to indicate that leveling can be started If there is no enough intersections appropriate error message is displayed and user cannot force program to start leveling quest NS gt Estimated profile intersections 122 e Can start leveling now Press YES to proceed E Warning Leveling can take long time Figure 57 Profile intersection count message After leveling is complete short results message is displayed as 58 This message states what method was used Least Squares or Robust what variable
95. use arbitrary projections 3 Installation MagPick is using the wxWin multi platform library and therefore exists in two forms Uxnix Linux and MS Windows NT 95 98 Uxnix like systems require compilation Binary is available for MS Windows platform 3 1 System requirements MagPick is C program which works under the Uxnix operating system The current version was developed and used under Linux Uxnix clone for PC s and the gcc compiler version 2 7 2 and above was used It is necessary to have X11 running because MagPick is a full windows client It is linked to the following X11 common libraries libXaw so libXmu so libXext so libXt so libICE so libX11 so libXpm so Selection of the system libraries can be different for another operating systems for Solaris2 x for instance MagPick employs netcdf library to read grid netCDF files Library is freely available A copy of the latest released version of netCDF software can be obtained using a WWW browser or anonymous FTP from ftp ftp unidata ucar edu pub netcdf netcdf tar Z Follow the instructions to install netCDF library on your machine To implement a graphics user interface GUI magpick uses wx Win C library version 1 6x which can be found on http web ukonline co uk julian smart wxwin There are different implementations of wxWin are available Libraries can be based on standard toolkits motif xview OpenLoolk or Athena widget set Xt In general ma
96. values overwrite the values defined in MagPick For ex ample the program uses the size defined here to label grid lines or draw profile direction arrows However the stack label text and arrow sizes are defined in 7 e Line width Presently not used e Color Default color for the layer If the User magpick colors box is not checked all layer entities have color by layer e User MagPick colors If this box is not checked all layer entities have color by layer If checked then the color is defined explicitely for each entity Magpick works in the short form of UTM projection Therefore all sizes above line style text and arrow are in meters If user requests transformation for example inverse UTM to present drawing 166 Export and printing in latitude and longitude see below these values are still in meters program will automatically recalculate appropriate sizes in degrees The user can enable transformation while preparing the DXF file The typical case is to have the DXF drawing in full UTM coordinates while internal MagPick picture is in short UTM just add Northing and Easting values Another case could be when the user wants to have a drawing in latitude and longitude To use this feature the user can press Transformation setup button This allows the program to transform coordinates in two ways e Linear transformation Xmagpick Ymagpick Coordinates are transformed as Xgrawing Xscale X Xmagpick Xof
97. where they all are selected Note that the dipole Ids are displayed on GE the same way as they are displayed in MagPick if they are enabled on the screen in MagPick they also appear as numbers on GE screen 22 2 4 Manual target locations This property is similar to the dipole property above but relates to the hand selected targets There fore additional information such as dipole parameters is not available and is not user selectable The user can only enable or disable this feature as well as control the ID position display in the GE balloon window 22 2 5 Additional drawings lines and polygons If user loaded an external drawings file to draw on top of the map these can be exported as separate entities into GE The following property dialog one property per one file controls the export 1 2 3 4 5 Enable drawing export Enables or disables this element for export Google Earth Folder Name Folder name for GE Line width This value overwrites value in the drawing file Minimum is 1 Use mono color for drawing Overwrites drawing color from file if checked Color When mono color is used see above this button allows user to specify color and transparency 175 Export and printing 29036 5462 H T 2936 55 Dipole ID 7 Sa Longitude 82 48 217010 W Latitude 29 36 325006 N Depth 1 23m Mass 0 62kg Model fit 1 93nT Angle w Earth s field 102 08 __ Dipole Inclination 17 72 29
98. with gnuplot using File Plot inversion graphs menu from dipole worksheet The picture shows inversion dialog Profile Inversion Parameters y 3 E x M Use all default parameters Source type Dipole s Main field Inclination deg 37 800 Background Square y Main field Declination deg 1300 Source seed Automatic y X axis azimuth deg 99 Magnetization 3D Full y Data type Profile defaut y Initial source depth m o Sensor separation m EA Sensor depth Spline smoothir o e None 1 line gt Smoothing parameter 1 0 003 Extension distance m fo E 2000 Try off line locations of length 20 How to report target depth Source depth Varible estimate From sea floor z J Create protocol DAT file in the inversion folder Select inversion folder Ok Cancel Figure 103 Profile inversion dialog Note that this is the same as for single magnetometer inversion The following controls are available 3 Alternatively user can use multiple lines in the inversion as it is done for single magnetometer This however is not very practical because of the individual positioning errors in each line It is recommended just to take line with the strongest anomaly 150 Array inversion Use all default parameters Check this to use intelligent guess about most appropriate param eters This disables all controls in the dialog Typically using all defaults is not recommended bu
99. 0 87gauss mass 226 5kg 1 Estimation based on magnetic map e Start MagPick and load file bomb grd Adjust the color and size to see teh picture better say set X Y cell sizes as 10 pixels You are now seeing a typical dipole anomaly right in in the middle of the window In real life there are another objects near by therefore we should constrain the area we are going to work with Go to zoom Edit Zoom Zoom the area from the bottom left corner 4 4 to upper right corner 14 16 You have now a second window where we will do our operations Now use the rectangular pick Edit Rectangular pick Show maximum area then min imum area The pick appears in the screen The middle point of this pick is the initial location of the dipole The mathematical solution needs to be given some initial geomet rical position which includes X Y Z e Go to Inverse Run Here you have to fill in the table Specify Main field inclination declination and azimuth of X axis latter is 90 degrees because X axis is going west east Enter total magnetic field and Susceptibility Remanent Let Margin space be 0 23To get mass estimated correctly locate file magpick ini or magpick on Unix systems and make sure that string TronDensity is set to 0 0078 228 Tutorial Number of iterations 4000 some big number Limit to stop equal zero Now important parameter is Initial depth Set it as 5 meters You should not set Density and J
100. 036 530N Dipole Inclination 170 52 an Magneic moment 310 cgs E 29936 32 aan F le a lit Hie Figure 124 Exporting dipole locations to Google Earth 6 Transparency Overall ransparency level for GE While in Google Earth the user can click on the drawing elements to display a balloon with the name of the file Individual line segments are not accessible 22 2 6 Additional drawings points This type of information is different from the segment drawing above and marks a particular point on the map Each point may have annotation text which can be displayed in the balloon and shown directly on the GE map The control dialog is shown on figure 1 Enable points export Enables or disables this element for export No point locations would appear in GE if the feature is disabled 2 Position annotation format Controls how the position is displayed in the GE balloon which appears when user clicks on the target The position can be displayed as decimals degrees and decimal minutes or degrees minutes and decimal seconds 3 Digits after dot This controls representation of the decimal part on the position balloon 4 Report positions as Depending on this selection positions can be exported as Lat Lon full UTM or short UTM coordinates 176 Export and printing External file drawing x M Enable drawing export Google Earth folder name MagPick drawing file Line width fi Transpare
101. 1 Enter inclination and declination of the Earth s magnetic field for your area If you do not know go to Inverse IGRF model and calculate it you need to know geographical coordinates of your place To use calculated parameters check Accept parameters for inversion and MagPick will use them when ever possible 2 Here is a similar set of parameters but for magnetization We recommend to start with the same values as with the Earth s magnetic field this implies induced magnetization only 3 The Azimuth of you local X axis It is 90 if it points East 4 Check this box if you want reduction to the pole and the four fields below will be filled in automatically If you want to recalculate field to the new directions you should not check box enter desired directions directly 5 You need this group if the results of your calculations are unstable Apply some upward con tinuation as a low pass filter it may help 16 Estimation of magnetic sources Along with the simple magnetic picking facilities MagPick has an internal option of magnetic mod elling Presently it supports only three kinds of sources uniform magnetised sphere magnetic dipole magnetized line and uniform infinite current power line It is possible to find a few sources simultaneously in case of dipoles or power lines Parameters that need to be estimated for each dipole are three components of the total magnetic moment of the body and three parameters X Y
102. 14 Simple profile loading 41 Basic operation of MagPick and Easting is recommended in this case because if they are not truncated to the short form loss of positional accuracy will occur If your data has position in degrees Lat Lon set False Easting and False Northing to zero In case of marine Geometrics magnetometer data Signal level field can be used to filter the data on input For 880 881 882 magnetometers low signal level value indicates possible invalid magnetic field reading To reject these readings check Filter by signal box You need also set correct column number typically 2 and signal rejection level value of 200 is a good choice for G 882 and G 880A and value of 400 is a good choice for G 881 and G 880 because this still may keep some valid data you may need to experiment with this choice Note that for multi sensor arrays only one signal from one magnetometer is used as a filter All data with signal less than this limit are not read in Press Add button and then use file selection dialog not shown here to select your data file Typical options are Surfer DAT file or Geometrics MagLog NT Interpolator file INT After file is selected program parses its first row and the bottom part of picture in Figure 14 appears Set the method to split into lines or No split if entire file represents just one line If you choose Distance then a new line is started when the distance between two points i
103. 2870 2860 2860 6010 6020 6030 6040 6050 6060 6070 6080 6090 6100 X m Figure 7 An Example of stack labeling Both realtive and absolute values are printed actual mag pick output stack labels realtive amplitude absolute Check this box to enable al to annotate value or both AFECTE i ri Use stack plot labels How to label Amplitude Label limit 10 000 Text hight 3 000 Digits jo Add text to Data units nT Color annotation Cancel Select label s color Do not label max and minimum values less then this limit Enter number of digits after dot for labels Set text high in distance units if plot in meters this value in meters too Figure 8 Stack label dialog e No color map Do not draw it at all e Simple color map There are no 3D effects here just plain color image Shaded relief Black and white shaded surface It allows you to see some details better e Color illuminated map Similar to above but colored 2 Light source parameters To draw shaded maps you must specify parameters of the light source such as its azimuth and elevation above horizon both in degrees Results are shown on the sun icon 4 3 Data scale Before the shade calculations take effect the data may need to be multiplied by some scale factor to improve the result This control sets this value You may need to
104. 3 Data smoothing 022 4654 2k be Ree Ree eRe ee RES CA AS 7 2 5 Computing IGRF values for profile data AAA AAA A RA E a 7 3 1 Simple SH 2 226 424 4 4 4 e464 62 dada Oe sc eee Beara Bo a A Be Seago Bode Ge adas cada RARA RE aa e a ERA a 7 4 Splitting profile lines in place 2 o e e TA Profile data export 4 2 oe oe me oe amp Ge EH RED ra 8 Removing polynomial background for profiles and grids 8 1 Grid operation es ok eh ere SE eek aria rr BSR ER 8 2 Profile operation lt 4 424424444 24 8 48 444046434 2748884 9 Leveling magnetic profile data with tie lines 9 1 Notes of the method implementation 2 00 4 9 2 Leveling operation 2d 2 wk ow o ohete oe oe ee 6 ew ee 10 Quasi Analytic signal 10 1 Brief introduction to the Analytic Signal o o 10 2 How quasi analytic signal is computed in MagPick 11 Simple magnetic anomaly positioning 11 1 Convert picks into targets grid OperatlOM o a 11 2 Picking targets directly from profile lines o o 11 3 Profile manual targets cae ee cba A A 12 Coordinate transformations 106 PARTE AE 106 pata dd A A 107 ci Soe eee SR ede oe ee BS we eS 108 cl a eed da Oe 109 pa o ee ee ee ee ee A S 112 atentas ie Golde deeded 115 ba oom a A RE eee 116 area 116 12 6 3 Example Louisiana South NAD
105. 561666 67 Northing 1616135 15 us ft Note the same result can be obtained with to statement init nad83 402 units us ft Note that 0402 is Corpscon projection code for California State Plane II but leading 0 should be omitted 12 6 5 Example ED50 Europe common offshore UTM Zone 31N This coordinate system also has name UKOOA and is based on ED50 datum which uses Interna tional 1924 ellipsoid Let s assume that data are already in UTM ED50 zone 31 and appropriate false Northing and Easting have been selected To output coordinates in Lat Lon ED50 we need to from proj latlong ellps intl may not need ellps intl to init epsg 23031 Here 23031 is EPSG code for ED50 UTM zone 31 Control point 52N 4E in UTM zone 31 ED50 Easting 568653 01m Northing 5761630 11m However if data is going to be presented in Google Earth Lat Lon output should be in WGS84 This means that 7 parameter transformation should be used This might be embedded in init epsg 23031 already however using Expand option shows that it is not In this case to should be modified as init epsg 23031 towgs84 89 5 93 8 123 1 0 0 0 156 1 2 and from as proj latlong datum WGS84 Here is control point of 52N 4E in WGS to EDS50 zone 31 Easting 568742 05m Northing 5761720 34m Use program PCTrans independently verify this conversion It can be downloaded from Royal Netherlands Navy website Note that rotation signs are reverted in PCTrans
106. 7 Select inversion folder Use this button to navigate and possibly create inversion folder Note for Linux users MagPick only offers simple string entry in this case Use file manager or ter minal window to obtain path as a string and then middle button to paste into magpick window path selection window MagPick distribution includes DipoleFit magpick file which is the test project for multi sensor TVG inversion The project includes real data recorded with TVG over known deployed target The pictures and shows inversion for two lines of the data one of which is about 5 m off the target Results of the inversion are shown in the dipole worksheet 104 E Inversion sheet dipoles currents etc i T X YE Z ref Fit Mass A M2 Angle Discr AMPL 1 P 7576 70 9321 54 0 34 burial 5 436e 002 3 8 33 5 96 58 7 641 2 P 7576 55 9321 15 0 23 burial 2 220e 002 3 5 24 3 97 45 2 992 Figure 104 Dipole worksheet inversion results 4Protocol files are not removed when target is reformed from worksheet 153 Array inversion Y meters 9315 F f oS ae i mai 9315 7550 7555 7560 7565 7570 7575 7580 7585 7590 7595 7600 marker DOWN X meters marker UP 7575 W y 7580 Magnetic Field nT EN E Figure 105 Inversion on the line close to the target Selected profile is shown in red on the map plot The matching profile plot is shown below Note profile markers to limi
107. 78155 rf 298 3 ModifiedFischer1960 fschr68 a 6378150 rf 298 3 Fischer1968 helmert a 6378200 rf 298 3 Helmert1906 hough a 6378270 0 rf 297 Hough intl a 6378388 0 rf 297 International 1909 Hayford krass a 6378245 0 rf 298 3 Krassovsky 1942 kaula a 6378163 rf 298 24 Kaula1961 lerch a 6378139 rf 298 257 Lerch1979 mprts a 6397300 rf 191 Maupertius 1738 new intl a 6378157 5 b 6356772 2 Newlnternational 1967 plessis a 6376523 b 6355863 Plessis 1817 France SEasia a 6378155 0 b 6356773 3205 SoutheastAsia walbeck a 6376896 0 b 6355834 8467 Walbeck WGS60 a 6378165 0 rf 298 3 WGS60 WGS66 a 6378145 0 rf 298 25 WGS66 WGS72 a 6378135 0 rf 298 26 WGS72 WGS84 a 6378137 0 rf 298 257223563 WGS84 sphere a 6370997 0 b 6370997 0 NormalSphere r 6370997 Table 2 Ellipsoids supported by PROJ library 117 Geographic projection transformations UTM and PROJ 10 11 12 13 14 15 16 17 init Most common usage is to define projection based on its EPSG NAD27 or NAD83 codes Examples are init epsg 2226 init nad27 402 a Semi major radius of the ellipsoid axis datum Datum name Most common are WGS84 NAD27 NAD83 ellps Ellipsoid name The table of all available is here 12 6 2 k or k_0 scaling factor tlat_0 Latitude of origin tlat_1 Latitude of first standard parallel Hat2 Latitude of second standard parallel tlat_ts Latitude of true scale lon_0 Central meridian proj Proj
108. A N Where Ax Az is defined in the profile coordinate system x z Now we can re write equation 1 as Az x xo 3 Axh ax h2 xx h2 Where xo is cable position along the data profile h is vertical distance from the data line to the cable J is a scaling coefficient proportional to the electrical current The values of x h J a and Toc ought to be estimated as result of the modeling The expression 2 could be re written as a x xo Toc Tinodel J 2 2 AyJz A Jy h x xo mn Ay Jy AJxz h x x0 5 2 2 x xo h x xo h Here are two unknown coefficients Jy and J define current amplitude and orientation of two parallel wires assuming that current is balanced This model is consistent with representation of two wires as a line of dipoles with magnetic moment Jy Jz Tmodel a x xo F Tpc 156 HVDC cable inversion 20 2 MagPick Inversion implementation To start with inversion first draw approximate location of the cable using polyline feature This is important because 1 Program will take intersections with data lines as initial locations of the cable crossings 2 Program will take into account angle between profile lines and the cable Figure 108 Draw polyline to approximate initial location of the cable This does not need to be precise After polyline is drawn go to the profile window and select menu Inverse HVDC cable
109. AD2 7 Arizona West Ok Cancel Figure 77 EPSG lookup dialog select appropriate projection and press OK Northing and Easting as part of proj string x_0 and y_0 However MagPick allows direct specification because of the importance of these parameters 5 Set offsets from data If projection dialog is called during data load simple load or load with template program takes data sample and enables this button It also sets false Norting and Easting automatically To restore them press this button 6 Calculator The sequence if controls resembling projection calculator User should check pro jection calculation using data available from the external source such as control points known in both coordinate systems Set False Northing and Easting to zero for this check In X Y fields on the left type data in from projection typically X is longitude Y is latitude West longitude and South latitude are negative To type in degrees and minutes or in degrees minutes and seconds separate these fields by space Press gt button to obtain projected coor dinates in to system in right X Y fields Button lt makes inverse calculation from to to from Advanced controls 1 Match UTM This button is used to switch between built in UTM projection to the PROJ re verse switch from PROJ to built in UTM normally not possible Let s assume that data orig inally was loaded using built in UTM and at some point user wants to use other
110. Altitude box is not checked MagPick may use values loaded as Depth or Altimeter channels Those are to be used with airborne surveys Selections are Fixed Loaded as Depth Loaded as Alt If box is not checked and middle point or fixed position mode is selected average elevation of each line is accepted for IGRF thus producing different IGRF values for different profiles Altitude fixed value This field is available when altitude is fixed for all profile data Altitude units Possible selections are meters feet kilometers Data Channels List all channels to be used for IGRF In most cases this field would have 1 entered For magnetometer array list all channels Example 1 2 Use fixed year decimal Check this box to overwrite date loaded with the data This box also must be checked if no time information is available for the profile data In this case approximate date of the survey should be entered as decimal year For instance September 2007 can be entered as 2007 9 12 2007 75 If box is not checked then each profile is used with its own 70 Profile data transformations date For instance if area was surveyed in 2006 and then in 2008 and data was loaded jointly with its time stamps different IGRF values are used for different profiles depending on profile date For middle point or fixed position modes average date of each line is accepted as IGRF year 9 Use Inverse UTM Because IGRF model req
111. Analytic Signal as a function of Inclination based on a dipole model This plot shows roughly how much signal is lost when a three sensor systems is replaced with two sensors and Quasi Analytic signal is computed in place of true Analytic Signal For more information please see 11 12 10 2 How quasi analytic signal is computed in MagPick At least two data channels should be loaded in the program such as it would be a case if data was acquired with the transverse Geometrics G 882TVG marine gradiometer or two concatenated ma rine magnetometers Alternatively a land G 858 sensor can be employed assuming land lines are long enough at least 100 200 samples or more Use Simple load as it is described in this manual see 5 5 and define at least two channels After the data is loaded the map window should be opened File New Grid Closely spaced survey lines for the individual sensors are typically seen The user may also open a profile view window to see field plotted in graph form However all profile windows should be closed prior to computing the analytic signal From the map window select Profiles Compute gradient as shown on figure 64 The following dialog 65 will open Below is the description of dialog 65 controls 1 Sensors separation Enter the separation between sensors in meters 2 Magnetic sensor s channel Enter the sensors to use In the general case of a magnetometer array of two or more channels any pair could
112. Analytical Initial cable depth m ho J Create protocols Inversion folder Ok Cancel Figure 109 Main HDVC cable inversion dialog 111 Active between marks Only active profile is used and user must use marks to limit data for inversion b Poly line name Name of the poly line used to approximate initial location Note that there could be multiple poly lines on grid view but only one is used c Use data window Check this box and specify data window in meters Data window is centered at polyline and survey line intersection and is counted plus minus from that point This entering 100 means that program uses part of the profile centered at intersec tion and extending by 200 m total d Channel for inversion In case of multi channel data only one channel can be used at a time Specify it here 3 Model parameters These include the following a Cable type Possible selections are pair of conductors single conductor or combination of both Note that wrong selection will produce erroneous results b Conductor separation Applicable only for two conductor cable used to estimate elec trical current in the cable c How to report depth Selections are from the sea floor from sea surface and from the sensor Note that altimeter and depth sensor are required for report from sea floor and depth sensor is required to report from sea surface If no altimeter nor depth sensor is available onl
113. CORNFLOWER BLUE CYAN DARK_GREY DARK_GREEN DARK_OLIVE GREEN DARK_ORCHID DARK SLATE BLUE DARK SLATE GREY DARK TURQUOISE DIM_GREY FIREBRICK FOREST GREEN GOLD GOLDENROD GREY GREEN GREEN_YELLOW INDIAN_RED KHAKI LIGHT BLUE LIGHT GREY LIGHT STEEL BLUE LIME GREEN MAGENTA MAROON MEDIUM _AQUAMARINE MEDIUM_BLUE MEDIUM _FOREST_GREEN MEDIUM GOLDENROD MEDIUM ORCHID MEDIUM_SEA_GREEN MEDIUM_SLATE_BLUE MEDIUM_SPRING_GREEN MEDIUM_TURQUOISE MEDIUM _VIOLET_RED MIDNIGHT BLUE NAVY ORANGE ORANGE_RED ORCHID PALE GREEN PINK PLUM PURPLE RED SALMON SEA_GREEN SIENNA SKY_BLUE SLATE BLUE SPRING_GREEN STEEL BLUE TAN THISTLE TURQUOISE VIOLET VIOLET_RED WHEAT WHITE YELLOW YELLOW_GREEN T Then you specify width of the pen O means 1 pixel pen other values show pen width in physical units of your map The line coordinates follow They can be as many segments as you need A pair occupies a separate string 2 Points If you choose to highlight some specific locations you use points To plot them prepare the file 32 Basic operation of MagPick POINTS 12 UTM 5 5 10 RED Point num 1 UTM 10 10 10 BLACK Point num 2 First line of the file has a magic word POINTS and the annotation font size in points This line should be always the same font size ca
114. CT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFT WARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE 10 History and features of Magpick 2 History and features of Magpick 2 1 Version 1 0 1996 1998 Development of MagPick was started in the spring 1996 The initial idea was to provide an interpreter with a simple tool which could perform basic operations such as e View a magnetic map with dynamic adjustment of a color scale in accordance with minimum and maximum grid data Narrowing the data interval could also be accomplished if desired Zoom of the different parts of the map and present them in separate windows automatic change of the color scale to fit data range in the particular window e Simplify magnetic picking This was accomplished by allowing the user to select two points with a mouse and store them in the file In many cases location of magnetic body 1s between minimum and maximum of magnetic field therefore two points are needed to estimate loca tion e Advanced magnetic picking The user selects regions where minimum and maximum are and program automatically finds their exact positions e The removal option erases picks that has been made This first version of MagPick was ready about one week after initial design began It was used to pick more then 1000 magnetic anomalies on map of Hamburg airport area Sophisticated options such as fitting of observed magnetic field by mode
115. Declination 16 56 Magneic moment 831876 cgs Q Right click drag to zoom T T T T channel 1 synthetic 1 channel 2 synthetic 2 E y 2 E 2 v o o 20 10 0 10 20 distance m from data point closest to the source Figure 143 Balloon with target information and anomaly graph MagPick supports two formats to include such images into KMZ files 1 PNG portable network graphics format In this case static image is included user have no ability to interact with it 2 HTML CANVAS guplot 4 5 or above is required This clickable zoomable image with mouse position reported in the left top corner example above It is Java script file created by gnuplot with HTML wrapper from MagPick with some common scripts from gnuplot installation to be included in the KMZ file as well Below this latter option is discussed Google Earth should be specially configured to allow this information to be displayed Without this configuration blank window shows up In the Google Earth please go to Tools Options menu and click on General tab Under Placemark balloons check Allow access to local files and personal data Without this change Google Earth blocks access to the local data for security reasons 1Google Earth manual says that it should allow access to parts of KMZ file in any case however it does not happen at least for version 6 1 197 Anomaly plots with gnuplot To enable this feature click
116. False Easting and False Northing should be applied to the planar coordinates These are values added to projected coordinates to reduce number of digits needed to represent them For the above case those could be picked as 4090000 m and 320000 m Therefore new short UTM coordinates are 6742 06 m and 2037 81 m with round off error of 0 0003 m As a rule of thumb short coordinate form must be used in MagPick by defining appropriate False Northing and False Easting There are three coordinate systems used by this software 1 Geographical coordinate system expressed as latitude and longitude with corresponding da tum This system is used to read write profile data ant to export results 2 Full projected planar coordinate system such as UTM State Plane etc This system is used to export data such as GeoTIFF or DXF as well as results of inversion Note that datum must match Geographical Coordinate system or datum transformation parameters such as 7 parameters or transformation grid file name must be provided 3 Short coordinate system This is working internal system All intermediate results are saved in the short system MagPick project files are also saved as short coordinates along with matching transformation parameters utm file Historically MagPick supports UTM projection therefore term short UTM is widely used in this manual and through the program Starting with version 3 20 this term loosely applied to any projection not
117. G button on the right gives quick access to EPSG lookup table showing EPSG codes and projections names as it is shown on figure 77 There is no guarantee however that all EPSG codes are supported 4 False Norting and False Easting Those are values used to reduce projection to the short form as it was explained earlier and must be used Note that it is possible to specify false SEPSG stands for European Petroleum Survey Group see http www epsg org and also http www epsg registry org 113 Geographic projection transformations UTM and PROJ Select EPSG code x Available EPSG codes EPSG 26720 NAD27 UTM zone 20N EPSG 26721 NAD27 UTM zone 21N EPSG 26722 NAD2 UTM zone 22N EPSG 26729 NAD2 Alabama East EPSG 26730 NAD2 7 Alabama West EPSG 26732 NAD2 7 Alaska zone 2 EPSG 26733 NAD2 Alaska zone 3 EPSG 26734 NAD2 7 Alaska zone 4 EPSG 26735 NAD2 Alaska zone 5 EPSG 26736 NAD2 7 Alaska zone 6 EPSG 26737 NAD2 Alaska zone 7 EPSG 26738 NAD2 Alaska zone 6 EPSG 26739 NAD2 7 Alaska zone 9 EPSG 26740 NAD2 7 Alaska zone 10 EPSG 26741 NAD2 California zone 26742 NAD2 California zone Il 3 NAD27 California zone Ill EPSG 26744 NAD27 California zone I v EPSG 26745 NAD2 California zone Y EPSG 26746 NAD2 California zone WI EPSG 26747 NAD2 California zone Il EPSG 26746 NAD2 Arizona East EPSG 26749 NAD2 Arizona Central EPSG 26750 N
118. Go to File Profiles Simple Load Press the button Add and choose file g 858m dat Set the following e Split 8 LINE e X 1X Y 2Y Data 4 BOTTON RDG e Active color RED e Inactive color BLUE Press Ok A new string appears in the list box Check the button Save as profile list Check that False Easting and False Northing are zero Press OK The file save dialog pops on the screen Enter the file name g 858m 1st Press OK MagPick indicates that 51 profiles lines were loaded Press OK You have read all your data into MagPick 2 Loaded grid data Go to File New and choose Profile view in the dialog What you see now was discussed above Go to File Interpolate grid Splines The dialog box Interpolation parameters with many fields appears on the screen Here what to do next e Under X parameters check Data limits This means that the horizontal extent of your grid will be taken in accordance with minimum and maximum values of the X coordinate in the data e Under X parameters set an interval 0 25 This is your grid cell size along the X axis in the grid we are going to interpolate e Under Y parameters check Data limits This means that the vertical extent of your grid will be taken in accordance with minimum and maximum values of Y coordinate in the data e Under Y parameters set interval 0 25 This is your grid cell size along the Y axis in the grid we are going to interpolate 221 Tutorial e Set Low constrain
119. L2 estimate is faster but L1 yields better results In most cases L2 is recommended If L1 is selected the warning dialog50 is displayed warning p WARNING eL L1 Robust estimate may take very long time depending on amount of data hours days You may not able to cancel during estimation Would you like to proceed with Least Squares L2 Fitting instead of Robust Fitting Figure 50 L1 estimation warning dialog 85 Removing polynomial background for profiles and grids If user answers Yes then program defaults to L2 method If user answers No then L1 method is kept The same question is asked again prior to start of actual computation 3 Retain results as Program can replace original field with estimated local field selection Dif ference grid model or with model field selection Model replace with model In any case original grid is not affected and result is saved into file selected below 4 Output file name Selects file with the new grid Press button on the left to call file browser 5 Output format Defines format to be used for the output file Possible choices are GS ASCII Surfer ASCII format GS BINARY Surfer 6 binary format and NetCDF GMT grid format To store in COARDC GMT 4 format use file name extension nc 6 Add file to the history list Similar to other grid operations it is possible to add newly created file to the history list for quick load After computation is complete st
120. MAGPICK magnetic map amp profile processing User Guide Mikhail Tchernychev 16 02 98 Beta version of the manual last revised 10 31 2014 Contents 1 2 4 Copyrights 6 LI MagPick Copyright Notice ooa e 6 ke a e amp a e pa e E e Ge ae A 6 1 3 Info Zip Copyright Notice 2 22314 al ada ada a a 6 Loira rre tica ri 7 8 1 6 The NetCDF Copyright ao oaoa 8 cha i oa o E e Pe Re SG 9 Ao re io e o 9 EEE a a Ee 9 History and features of Magpick 11 2 l Version 1 0 1996 1998 ss ek Ra ra a a e 11 22 Version 2 0 19908 19008 nmi ia ea Blah a a 12 2 3 Version 2 x 2000 2004 a a aw ee 13 24 Version 2 8 3 00 2004 2009 o ee eee 14 2 5 Version 3 20 2009 2011 caridad AAA 14 15 3 1 System requirements o o ARA RR A ORR ERK RR 15 E dns Ge a aa A A e 16 aus et AA A A ee 16 MagPick project files 16 4 1 MagPick project file internals o e ee 18 AI 19 20 5 1 Magpick as map grid viewer o oa aaa ee 21 5 1 1 Transforming equalized color palette into gradient 31 5 2 Drawing and clipping on top of the map oaa o 32 5 2 1 Magpick vector formats lines polygons points clip area 32 5 2 2 Bringing an AutoCAD DXF drawing into Magpick 34 5 2 3 Using ArcInfo TM shape files in magpick 35 EA e E A E 35 A III 35 5 3 2 PICK EXPO s ca ssu bok a be See RARA 36 DA
121. Min 0 Max 2500 Interval 100 Press Calculate See that levels 0 100 200 2500 are created Now uncheck Fast drawing and check Label contours Set the distance between labels as 4000 This means you want your lines annotated every 4000 units along the contour Set label length as 1000 This means there will be a gap in the contour of 1000 units to fit annotation text Press Ok In the current program version the progress indicator is not clear for this kind of drawing you have to wait about 1 5 minutes to have job done for Pentium 200 MHz PC Printing your map Magpick printing capabilities are limited They allow you to have at least a hard copy of what you did The printed picture will always be fitted to your paper Therefore it is impossible to choose the exact scale you want this may be be changed in future versions Here is how to print Go to Options Title to set X Y titles Y title never appears under MS Windows and general text above the plot Also choose the font size in 1 72 inch units I recommend something like 10 you may pick different values depending on results Press close Now go to Preview A blank page will appear on the screen this is one of the problems to be solved This is acceptable press Print setup your printer if need page orientation size etc Press Ok The job is going to be printed Take the page from the printer when it is ready MagPick produces big print jobs mostly under MS Window
122. On data load set from as init epsg 2226 State plane NAD27 US foot and set to as init epsg 32610 UTM zone 10 WGS84 Note that you also can set to as proj utm zone 10 datum WGS84 with the same result Set false Northing and Easting 2 After data is loaded go to UTM Setup dialog and change from to proj latlong da tum WGS84 or init epsg 4326 from the EPSG look up table which corresponds to WGS84 datum Now Lat Lon in MagPick is coordinate in WGS84 If you export geoTIFF file it is referenced in WGS84 3 Save profile data using Lat Lon options Profiles now in longitude latitude of WGS84 12 7 Adjusting depth and altimeter units for non metric projections Some of the cartographic projections notably almost all US State Plane coordinate systems use foot or US Survey foot as planar units This requires other distance measurements such as depth and altitude to be in the same units for inversion to work properly The typical scenario is when data is recorded with Geometrics MagLog software in this case coordinates are recorded as Latitude and Longitude in decimal degrees and depth and altitude is recored in meters After data is loaded into MagPick coordinates becomes feet but depth and altitude is still in meters 120 UTM Gauss Kruger transformation OBSOLETE Linear transform field x Linear transformation T a filed b What to transform All profiles v Transformed color SPRING_GREEN v Dat
123. Parameters X parameters X min 0 00 X max 200 00 imi Interval Y parameters min 0 37 Y max 99 64 F Data limits Interval Format NetCDF gt F Filter data recommended Method Average value gt Output file data misha projects magpick t grd Set file name for result Set format for output file y Filter data prior triangulation to remove duplicate points and reduce total number of points for triangulation Figure 21 Gridding profile data with triangulation 6 1 1 Triangulation with linear interpolation One of the primary methods employed by MagPick to interpolate a map from scattered points profile data is triangulation that follows by linear interpolation inside triangles MagPick uses the method described in 4 to build a Delauney triangulation network Then each triangle is used to find inter polated field values into regular grid cells This method works well in case of relatively uniform distribution of data points However results may not look good if there are only a few profile lines separated by considerable distance Also note that grid nodes outside the triangulation network do not get any field value attached Thus the method provides some natural clipping of the data 52 Grid operations Potential problems arise when data set has duplicate data points or points too close to each other Triangulation
124. SE INCLUDING WITHOUT LIMITATION ANY WAR RANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL INCIDENTAL INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE AND ON ANY THE ORY OF LIABILITY ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFOR MANCE OF THIS SOFTWARE 1 9 LIB GeoTIFF Copyright notice Copyright c 1999 Frank Warmerdam Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software Copyrights THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EX PRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MER CHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRA
125. Type The selections are outlined above and the following 1 Trivial half distance between markers 2 Intelligent with signal classification 3 Approximation with signal classification For cases 1 and 2 all dialog controls except Channel and How to report depth are disabled 2 Channel to use for pick Regardless of where markers are set the channel is selected here 3 How to report depth If depth sensor and altimeter are available depth can be reduced to water surface or sea floor using median depth and or altitude between markers Note that program does not take into account possible slope in the floor topography between markers 4 Dipole to monopole ratio Value used to identify anomaly as a monopole or dipole Please see figure 88 for the concept In many cases 1 is appropriate value but could be fine tuned based on the actual data 104 Simple magnetic anomaly positioning Number of targets for approximation Program can use multiple formulas above simultane ously to approximate curve It is useful when multiple anomalies are recorded close to each other If resulting values xo z are too close to each other approximation is not accepted and warning dialog is posted Most the time 1 is used if more than one target is entered keyboard short cut always brings up the dialog Use amplitude constrain to accept result Program computes amplitude of the dipole approxi matio
126. Unix 16 contour lines isolines contours 23 automatic levels color custom 24 fast 24 interval 24 labels min and max total 23 contours isolines 23 coordinate mesh color 23 show 23 step copywrite 6 Corpscon 202 dipole DXF export from magpick using in magpick 34 export BMP 171 CAD systems 159 DXF 159 Export to Google Earth dipoles drawings 169 image 166 points 170 profiles 167 targets 169 GeoTIFE 171 GPX waypoints export TIFE 171 forward problem 135 grid mosaicking clipping grid 55 creating path 54 data filtering operations preparation save spline gridding supported formats triangulation XYZ export grid cell size 21 history IGRF 124 coefficients file 124 use for inversion 124 241 INDEX use for reduction to the pole 124 installation MS windows inverse problem 136 inversion 128 automatic batch 134 grid data HVDC cables 149 mass estimation 134 Pipe lines 155 profile data 131 output format result worksheets 133 signge magnetometer theoretical basis 135 Latitude and Longitude grid 49 layback calculations Leveling operation locating of magnetic objects magnetic line 20 magnetic properties estimation 137 makefile Unix map color color illuminated dummy information shaded relief simple color
127. Use profile markers to limit the the anomaly Try to include the whole anomaly similar as it is show on the picture above 140 Single magnetometer inversion Mag field nT 8600 8650 8700 8750 8800 8850 8900 8950 9000 o An a 0 O Ss 43050 E A 43000 Y short Norting 8600 8650 8700 8750 8800 8850 8900 8950 9000 Figure 90 Profile view of the active data line Now go back to the map view above and note marker locations Next step is draw a polygon which will include anomaly and adjustment lines We can include one or two adjacent lines On the Map view right click and select Add Add polygon as it is shown on figure 91 Use mouse to create polygon similar to shown below Note that double click closes the polygon We need to make sure that program will actually use this polygon to constrain the data Click on the polygon s border to select it and then right click inside and select Edit from content menu alternatively you can double click on polygon border or right click on the map go to Add Edit all and edit polygon properties from there Ether way polygon properties dialog will be shown as 93 Now go to the profile view and start inversion by selecting Inverse Run from the window menu Note that we can t use default and need to adjust parameters here Most important parameters are shown in red Please see MagPick manual for additional details 1 Extended area Polygon It means tha
128. WN markers This is the sum of two previous operations UP and DOWN markers must belong to the same line Then program counts points from the start of the line and removes all data before first mark and all data after second mark The mark order is irrelevant either UP or DOWN marks can go first e Cut between UP and DOWN markers This is different from the previous operation in that it acts between the marks Important Data gets removed not interpolated After you have saved the profile it has less data points then the original one it also can have a gap and can be splitted into two profiles if you load it with a split by distance Figure 28 illustrates possible cutting operations 7 2 2 Removing turns from profile lines Some surveys are recorded continuously without breaking data into set of lines This is typical for marine surveys performed with a small boat when the working environment does not permit op erator to control logging computer or for surveys were operator has to also maneuver the vehicle Magnetometer positions computed on turns have larger errors than positions when the vehicle path is linear and therefore are generally not used for interpretation and display The magnetometer can also drop on to the sea floor get too close to the boat or enter into a dead zone for Cesium units yielding unusable data For these reasons it is generally beneficial to remove turns before data pro cessing This certainly can be done by h
129. Y value Italic text shows the nodes which MagPick uses to simulate clip Shaded area is white polygon drawn to simulate the clip Normally we assume only one clip for a map 33 Basic operation of MagPick The order of points is not so important for screen clipping but for postscript output it is crucial The order of drawings in the list is important MagPick does drawing in the following order 1 Color map 2 Contours if need 3 Profiles if loaded and required 4 All drawings in the order they appear in the list It means the clip will affect only graphics which are listed before clip itself plus the colored map and isolines 5 Coordinate mesh and additional text if need 5 2 2 Bringing an AutoCAD DXF drawing into Magpick In many cases users can have their maps in AutoCAD TM format Magpick is not capable of reading directly neither DWG nor DXF formats however some simple steps and using third party software allows a DXF drawing to be brought into MagPick relatively simple To use this option the user should download DXF2X YZ program available from GuthCAD http www guthcad com au freestuff htm for free This tool working under MS Windows only allows the transfer of AutoCAD DXF files into a simple form of ASCII file Please note that the program can be used for free but not redistributed Also see its license for industrial usage The problem with this program is it can not handle AutoCAD text and ellipses The use
130. a points along the track You might check the button Apply transformation in reverse order This is useful if your data has a reversed order in the file Enter shifts along and perpendicular to the profile The latter is positive to the right if you look along the track and negative to the left To apply a perpendicular shift the program finds a normal vector at every point of the path Shift along the path is positive forward To transform first point of the track program needs to find a direction of motion at the beginning of the line To do so it uses first part of the track being approximated to a straight line The distance used for such an approximation is entered under the Distance to find direction This value also used to find a direction at every point of the line This value can not be zero Finally chose the color to plot the transformed positions This selection allows you to preview the result and compare it with the original positions Note that the stack is not plotted it may obscure all the picture After you press the Ok button the program redraws the current map view any other maps you have to redraw by hand You now have a chance to compare the result with the original track If you want to repeat you just do it again The previous result will be automatically discarded To accept changes go to Profiles Accept All the original profile data is replaced with transformed data of course only for profiles where you did trans
131. a scale a 3 28084 E 4 Data bias b lo Channels to apply Apply transformation to Depth amp Alt y jera O E EE Ta es TEE Figure 79 Scaling depth and altimeter channels from meters to feet The conversion coefficient is 3 2804 feet per meter Note that all channels should be listed and Depth amp Alt is selected To cope with this scenario user should call Edit Linear menu from profile window The dialog 79 1s used to linear scale data as well as depth and altimeter readings The dialog 79 normally used to scale the data but can be also used to scale altimeter and depth channels The scaling is cumulative it means that if scale coefficient a is applied user should use 1 a to return to the original data In case of error user is advised to re load all the data If depth and or altimeter channels are scaled the warning dialog is displayed as OOOO hl Depth and or altimeter values are selected for transformation The results will be in place immediately no need to accept Note this affects magnetic moment estimations as power of 3 of the conversion Factor from meters to other units Press Yes to proceed or No to cancel operation No Figure 80 Warning dialog on altimeter and depth scaling When user presses Yes scale and bias are applied to the depth and altimeter channels directly there is no Preview function available Note magnetic moment and mass are scaled b
132. active profiles 82 Profile data transformations all profiles If a clipping polygon is used there are two additional selections all inside polygon and active inside polygon 2 Output format Possible selections are e X Y Text General data file with position X Y and annotation text e Magpick points This format can be used with Magpick to load results as additional point drawings menu Options Drawings e MagPick lines This format can be used with Magpick to load results as additional line drawings menu Options Drawings e MagLog points Format to be used as background for MagLog data acquisition program in form of marks e MagLog lines Format to be used as background for MagLog data acquisition program in form of lines 3 Annotation type The choices are e Data Data value typical is magnetic field Depth Depth sensor reading e Alt Depth Sum of depth and altimeter readings This indicates total water depth and could be quite useful for instance water depth can be plotted each x meters along the profile line as a reference e Data Line Depth Line Alt Depth Line The same as above but line number is added after the slash 4 Interval m Interval to export the data in meters For instance if interval is 10 m one data point is produced on 10 meter distance along the line 5 Median samples If this value is not zero program exports median value instead of raw data value Half s
133. agnetization and infinite ends In addition to the properties of the central segment properties of infinite ends must be estimated too This way we try to model a situation with final segment included into long pipe e C Equidistant parts with different magnetic properties Magpick divides the pipe on number of segments with different magnetic properties and tries to find Jy Jy Jz for each segment Number of segments are defined by the user This should be used to model the case when just a few 1 or 2 survey lines cross over each pipe segment e D Equidistant parts with different magnetic properties and infinite ends The same as above but plus Jy Jy Jz to be estimated into infinite ends Similar to a magnetic dipole case the pipe determination can be based on gridded magnetic data or on profile measurements Because of asymmetry of the object we would recommend primary usage of profile data Interpolated grided magnetic data can contain considerable errors for this kind of a magnetic signature this is of course function of area coverage Goal Based on a simple example we will learn how MagPick can be used to find the location of the pipe segment We will use case B based on profile data Files under tutor pipe Find here file dummy grd line1 5 dat lines 1lst and file field txt The last one holds the parameters of the Earth s magnetic field for a place where data was taken File lines 1st is a ready list to load into MagPick
134. al_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT ile Martinhal_201210_03 Survey INTERPOLATOR INT OO ATA be gt gt lt Subset Delete ee Close Profile information Total samples 6540 Figure 40 Original line names are shown in red box Operations Profiles Window Help Interpolate grid Shift XY Smooth XY External smooth XY Drag profile s 6700 Compute gradient Remove turns Cut profiles Remove short lines Auto Max Min pick Background acces t Level using tie lines i Total profiles length Report intersections Export lines numbers Accept Discard Can not split profiles Please close all current profile views Figure 42 If some of the profile windows are on the screen program cannot proceed 79 Profile data transformations Cut Split profile lines How to split Keep inside polygon s Split distance m 5 eee eee eee ee eee See ee en ee eee eee eee re eet ee eee ee peewee eee epee A RA A 0 oe oe ee dene enn eee genes
135. all data sets or use this only once for first data set and set the rest as manual UTM see profile simple load e Load these new profiles into freshly started MagPick Decimate the data if you need to e Re grid data all together You can use Quick grid because data is already well represented 6 6 3 Exporting data from MagPick to Geoplot 3 00 experimental This section covers in details how data can be brought into Geoplot software package This software is very picky about acceptable data format therefore need to detailed description The procedure was tested with Geoplot 3 00 MagPick part Magpick can export grid files in the format to be imported by Geoplot via conversion to XYZ files Here is brief outline of the procedure 1 Load profiles into magpick see manual Now profile data can be gridded with any available gridding method but special requirements should be met e Geoplot accepts only fixed set of possible grid sizes Those are 5 10 15 20 30 40 50 100 200 500 and 1000 meters Pick grid size from this set for gridding in Magpick For instance grid size of 15 x 30 m is legitimate while 12 x 20 is not Set minimum and maximum X Y values in the gridding dialog by hand so span of the area matches above parameters 59 Grid operations e Set cell intervals from the values supported by Geoplot Those are 0 0625 0 125 0 25 0 5 1 2 5 10 and 20 m Select appropriate value for interval as any other int
136. and AutoCAD dxf files 27 6 Finding magnetic pipes Preface Some elongated magnetic objects like metallic pipes can be approximated with a simple source such as magnetized material line This line is infinitely thin and has a magnetic momentum This kind of source can be infinitely long or may have a finite length It is certainly not a real pipe but at the distances much greater than the pipe diameter it provides a good approximation MagPick employs this model for locating of pipes or similar objects Practice shows that this kind of object rarely can be considered as infinitely long therefore a simple infinite length approximation won t work Things are even worse most of the magnetic field observed from pipe sources are due to the section joints not from the linear part of the pipe To cope with this problem MagPick provides several user selectable modifications of search see figure 164 e A Simple segment with uniform magnetization To be estimated geometrical location in XOY plan we assume constant depth for all segment and 3 components of magnetization Jx Sy Jz 233 Tutorial A simple piece with uniform magnetization B simple piece with uniform magnetization and infinite ends equidistant parts with different magnetic properties de ers 1 2 3 D 1 2 3 equidistant parts with different magnetic properties andinfinite ends Figure 164 Modification of pipe model e B Simple segment with uniform m
137. and using the cut profile feature but this operation is time consuming and can be tedious Another option would be to use a polygon to clip profiles but this does not work if there are turns inside survey area Magpick allows automatic turn removal using the simple approach described below Figure 29 illustrates turn removal method 1 Using user defined turn leg distance program first should find three points A B C so distances measured from A to B and B to C along the boat track is equal or greater of the leg distance use closest data points 2 For each of those A B C points find angle a If this angle is greater than the user defined limit typically 90 to 120 then discard points A B C and find another three points If o smaller then user defined limit accept points as a turn 64 Profile data transformations Figure 29 Automatic turn detection algorithm 3 Start moving from point A to point B and from point C to point B using data points For each points A and C compute angle between vectors AA and CC If this angle is less then user defined limit keep going to the point B If angle exceeds user defined limit stop 4 Finally remove path between points A and C It should be pointed out that automatic turn removal works best if there are a sufficient number of similar turns so turn removal parameters can be tuned for a typical turn However some turns may not be automatically removed for instan
138. ap using simple pick or rectangular picks see 5 3 Now all picks can be converted into permanent targets from the Select Inverse Pick into target menu The operation sequence is the following e Program asks confirmation if all picks are to be converted into targets Note that original picks will be removed from the map e Program let user save original picks into pick file User should assign file name and save the data If Cancel is pressed program skips this step and picks are not saved e Program actually removes picks from the map and replaces them with manual targets Those are shown as where is target number The same numbers are used in the spreadsheet If there are any existing targets in the spreadsheet new targets are appended to them Program uses middle point of the pick as target location After this operation the map has target marks and the spreadsheet is filled in with targets This worksheet can be accessed from Inverse Work sheet Targets menu It s operation is pretty much the same as any other worksheet dipoles pipes in the program The figure 66 shows targets work sheet ER Manual targets sheet Grid functions G 9353 41 7270 06 16 98 Load Save Delete AAA Undo Clear all Format positions Figure 66 Manual targets worksheet 100 Simple magnetic anomaly positioning Most important are the X and Y fields Because target was acquired from
139. ap view This view dependents on the parent map view Only one profile inversion view is allowed for a given map view The last views are unaccessible before the profiles are loaded This means that when the program opens you are able to create only the map view When you choose New item a new empty window with the same menu appears on the screen If the profiles were loaded then by choosing New you can the type of view you want In the following sections a discussion is developed in detail for each mode of operation 5 1 Magpick as map grid viewer Just after the start of MagPick go to New and request a new window Then click Open and you can choose netCDF or SURFER ASCII or binary grid file to load into window After the loading is completed which take time depending upon size of the file you end up with a colored map on the screen Alternatively you can click Open point directly If you choose this option in the root menu a new window is created automatically You can change size of the window and therefore resolution by means of Options Size item Here you are able to choose three values horizontal size of one grid cell on the screen in pixels vertical and zoom factor when you are zooming in part of the map Be careful large sizes can consume all the memory of the computer You may find Autoscale on zoom is useful It means when you create new window by zooming part of the old window color scale into this new w
140. appropriate box on the dipole export property dialog while exporting into Google Earth shown on figure Dipole export xj peressesesoesssoccssesseossesosossocesocsseosossesosesseseeg AA A S Position annotation format Degrees minutes Digits after dot f Report position as Lat Lon C Full UTM C Short UTM M Report observed synthetic fit M Report approximate mass MV Report dipole angle with Earth magnetic field M Report dipole inclination angle M Report dipole declination angle M Report dipole magnetic moment cgs MV Report amplitude M Report fidelity M Report count IV Include anomaly plots Gnuplot parameters Ok Cancel Figure 144 Google Earth dipole export parameters The last check box Include anomaly plots should be checked Press Gnuplot parameters Dialog presented to the user is identical to the one for creating anomaly plots The differences are 1 Only two formats PNG and HTML CANVAS are allowed 2 In case of HTML CANVAS user must specify js folder with gnuplot provided Java script to handle mousing etc These typically reside in the gnuplot installation folder such as C Program Files gnuplot share js Under Linux this folder is typically usr share gnuplot gnuplot 4 4 js replace 4 4 with your gnuplot version User also can use his or her local copy of gnuplot js folder to modify java script files The entire content of this folder ought to be copied into KMZ fil
141. as PDF To set paper size under GS View use Media menu 183 Export and printing 22 6 Using GSView This section summarizes some GS View issues Please see Ghostscript GS View manuals for more in formation Note that you can print and convert your map into the variety of formats using Gshostscript 22 6 1 Printing via GSView To print file from GSView select File Print from Gsview menu Make sure that Printing method at the bottom of the dialog is set to Windows GDI printer Select printer and other settings and press OK button 22 6 2 Converting PS file to PDF To convert loaded PS file into PDF select File Convert from GSview menu In the left side of the dialog select Device pdfwrite as it is shown on screen shot Convert xj Device Resolution pdfwrite 2 Cancel Properties Help Variable Page Size y Reverse Odd Pages Options i Figure 130 Converting PS file into PDF uisng GSView In most cases Resolution settings do not affect the plot If you plot includes a color map Ghostscript can use JPEG compression to reduce image size This typically yields smaller PDF files However it is possible to get a blurry effect due to JPEG compression algorithm To avoid this press Properties button and scroll down to EncodeColorImages as shown on figure 131 Make sure value is set to false This will produce a much larger PDF files but with no blurry spots near the edges
142. as by min data value and High constrain as by max data value This means that the interpolated grid can not have values less or more than initial data set e Set Tension as 0 25 and Format as GS ASCII the last means Golden Software ASCII Set Iterations to 250 It should be enough for most cases e Set Convergence limit 0 Press Output file and enter name g 858m grd This is where the result of the interpola tion will be stored as a grid file e Advanced read article Smith and Wessel Geophysics 3 293 305 1990 to learn more about this interpolation method Press Ok and wait until the program completes interpolation You are seeing the progress dialog Gridding is working which shows the iteration number and discrepancy for the current step It can take from several minutes to complete interpolation View interpolated map Go now to File New and choose Grid view The empty window appears Check Options Size set X and Y sizes as 1 Then check Options Settings Here is what to do next e Check Autoscale e Check Show x grid and Show y grid Set X Y as 10 e Uncheck Snap to grid and Contours we do not need this checked for now e Check Show profiles in the configuration dialog Profile plot parameters uncheck Show profile direction and Plot stack profile press OK e Check Color map in configuration dialog Color map draw mode set Drawing mode as Simple color map and press OK e Press Change palette select Un
143. ase the temporary folder is deleted after operation is complete Files in the temporary folder are not copied into the current user folder except user drawing files and profile line shifts file The typical content of the archive magpick3 zip is show below nagpick3_1 annotations agpick3_1 ini agpick3_1 nc agpick3_1 pick agpick3_2 annotations agpick3_2 ini agpick3_3 annotations agpick3_3 ini agpick3_4 annotations agpick3_4 ini agpick3_4 nc agpick3_5 annotations agpick3_5 ini agpick3_com ser agpick3_dipoles tbl agpick3_global ini agpick3_pipes tbl agpick3_profiles dat agpick3_profiles lst agpick3_profiles_2 dat agpick3_profiles_2 1st nagpick3_targets tbl Y Ss 8 S amp S E 8S SS 4 8 063343393 0224383494832 Y 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 All file names are created with the same prefix except drawing files which keep their original names All files are saved in local short UTM coordinates The following file types can be seen 1 SER Serialization control file to load the rest of the archive Only one file per ZIP acrhive is used my MagPick This is text file 2 NC grid data saved in NetCDF COARDC format Typically each map window produces one NC file however zoom windows share the same grid information and therefore only one NC file is produced 3 DAT LST files profile data and corresponding list files Note that All profiles in the window Inversion profile data is saved into separate file
144. ata after you did Accept use Edit Reload The original values will be restored from file and result of transformation will be discarded To make a change permanent you must save the profile File Save You will need to construct a new profile list file or use Simple load to load the data next time 7 2 5 Computing IGRF values for profile data It can be desirable to compute International Geomagnetic Reference Field IGRF values for a se quence of profile data loaded into MagPick To use IFRG profile computation activate the Profile View window and go to the menu item Edit Compute IGRF The following dialog 33 is shown The meaning of each of the controls in this dialog is described below 1 Where to apply Depending on this selection IGRF can be computed for active profiles or for all profiles 2 Positions The following computation schemes are available e Middle point of all data For small areas lt 10 km IGRF value can be assumed con stant This saves a lot of computation time MagPick can use the middle coordinates of the area to compute IGRF only once and then apply the computed value to all profile data The middle point is taken automatically based on profile position data assuming that UTM projection is used User is not required to enter Latitude and Longitude This option fits best for typical MagPick data sets The computed field is constant unless date and elevation for each profile is taken individually F
145. ations can affect profile views and the map views For example if you cut part between marks using the profile view you need to update redraw map view by calling Redraw function e Also you should know that the profile data can be loaded with a different resolution decima tion For example only each 5th data point could be loaded Any transformation you do in MagPick affects only the loaded points not all the points in the original file 7 1 Saving and re loading profile data Profile data can be saved by calling File Save menu item in the profile views or by calling File Profiles Save in the map views Remember that if Profile inversion or All profiles in the window is used the operation will be applied only to the profiles in current view After the menu item is called a user should choose name of the file to save the data The next dialog appears on the screen and gives the following choices e Save all profiles This means that profile data is saved If you are operating with the global profile list all loaded data is saved If you are working with All profiles in the window profile inversion view then only profiles crossing parent map window are saved e Save active profiles Only active highlighted profiles get saved When working with a global profile list only one profile can be active at a time All profiles in the window allows you to have more than one active profile e Save between the marks You can set user marks
146. atus dialog51 is displayed Ss 8 x 1 Least Squares Estimation by SYD Model fit 57 6146 Figure 51 Computation status dialog In this example dialog states that Singular Value Decomposition L2 was used for the estimation and fit between measured field and the model is 57 6 nT After user presses OK button newly created grid file can be loaded via File Open menu or file history list 8 2 Profile operation Profile polynomial estimation is very similar to the grid estimation but does have some differences Actual profile measurement X Y locations are used to estimate the model These locations are re duced to the center of the area before estimation is started User can replace profile data with the local field or with the model right after computation is complete or can preview the results using profile view In latter case results are accepted or rejected from the profile view window menu If profile data is loaded profile based polynomial model is available from the grid window under Profiles Background menu The following dialog52 is displayed when menu is selected This dialog52 is pretty similar to the one described above for grid operation The differences are 1 Channels Space or comma separated list of the channels used in the operation if more than one data channel is loaded for instance for the transverse gradiometer with two sensors it should be 1 2 In most cases this would be just 1 86
147. ays correct under Windows but here is a trick hold right mouse button and drag A bit more go to Option Size and set X cell size as 5 and Y cell size as 1 Press Ok Notice the difference An important lesson can be learn here if your grid cell size in the file is 5 x 5 meters in order to see the picture undistorted you must choose sizes like 1 x 1 2 x 2 3 x 3 Do not choose sizes where X cell and Y cell are different If your real grid cell size is 2 5 x 5 meters the undistorted picture will appear if your choose 1 x 2 2 x 4 etc Note that unfortunately not every grid cell size can be viewed undistorted Therefore grid your data preferably with equal steps along X and Y Now go back to the 1 x 1 size Zoom a picture We just have learned how to zoom all the picture Very often all what we need is to see some part of the big map Here is how you can do it e Got Edit Zoom the mouse cursor changes its shape e Press the left button and drag release the button Part of the map appears in a new window Note that if autoscale on zoom is checked when old window is active the color scale in this new window automatically adjusts to the local in the window minimum and maximum of the data Therefore you have your full color scale in a narrower range and can see your data better This new window can be zoomed again and again There is no limit on the zoom number Unfortunately MagPick has some problems with zooming near th
148. bels Controls which parts of the map frame should be labeled 6 Digits after dot Controls annotation format It s again defined by the selected annotation type degrees degrees and minutes degrees minutes and seconds Depending on selections this defines decimal places in degrees minutes or second After dialog is completed map should be re drawn This can be done by selecting Edit Redraw menu of by right clicking on the map and selecting Redraw from content menu It is possible that geographical grid parameters should be re adjusted repeat operation with new parameters In general Latitude and Longitude lines are not straight and do not coincide with UTM grid 50 Grid operations 5 7 Printing MagPick has printing facilities which are implemented thought the Preview menu for all types of views To make a printout simply open Preview A separate window with a page pops on the screen and you can see a preliminary plot This view is not exactly the same you will get on paper To make sure print it to the postscript file and view it with Ghostscript Note that MagPick always scales the plot to fit the given paper size In Print setup dialog box you are able to choose the printer file paper type and portrait or landscape mode Landscape mode is not shown in the preview but the printout is correct Each view window has the menu Title where you can set some additional features of the plot such as axis annotations com
149. bject Start MagPick and load file bomb grd It has just 35 x 41 cells go to Options Size and set the size of X Y cells as 10 Now you can see it better If you turn off the color equalization Go to Options Settings and then Change Palette Uniform and uncheck Equalize color you are seeing a classical field from a magnetic dipole To make life better set the coordinate grid with steps of 2 x 2 meters Ok Now where is the object is really located There are minimums and maximums on the map in front of you Simple theory predicts that object somewhere in between on the line which connects these two points say half a way So we can now locate it Go to Edit Simple pick Cursor becomes Go where you think maximum is click the left button Now the dashed line is started at that point and follows the mouse Go where you think minimum is Click again A solid black line segment appears This is the magnetic pick Perfect The middle of that line is probably where bomb is Now it s time to explain some points in the Common parameters dialog box if you check Snap to grid then start and end points of the pick are snapped to the middle of nearest grid cell If you have worked with Corel Draw or Surfer this should sound familiar If it is not checked they stay where you set them Check box Show crosses enables you to draw small oblique crosses at the end of the pick Try these two features to see how it works To see the cells better you can zoom
150. case the program operates with a global list of profiles in the first case it operates with a local copy of part of the list e Set marker Put a special mark on active profile There are two kinds of the marks see figure 118 and they can be two marks of any kind only When you click first time marker 1 appears When you do it second time marker 2 Third time you click marker 1 is removed from its location and set in the new place and so on Any marker is set in the nearest profile sample and appears on the both views profile and map view Thus the location of specific points can be easily found A Y Global profile view markers A y Local profile inversion markers Figure 18 Profile markers 5 5 5 Parameters of the profile view Profile view and profile inversion view have menus types different from the map view The most complicated item is Parameters Settings When you invoke Parameters Settings dialog box shown on figure 19 appears on the screen You you can specify all necessary information to make the most convenient view of profile infor mation It is important to understand that profile view can work in two modes 1 Shrink to canvas In this mode the drawing area has a fixed size and the profile is scaled in accordance of the minimum and maximum of the data It means that the profiles of a different length and amplitude will always occupy the same area on the screen It is difficult to compare them but you see al
151. cated in SUSERPROFILE Application Data magpick The following has to be changed WINDOWS_CODING CodePage 1251 CharacterSet 204 ModernFontName CourierCyrPS SwissFontName ArialCyrMT RomanFontName TimesNRCyrMT ScriptName ArialCyrMT DefaultFontName ArialCyrMT CodePage and CharacterSet control screen fonts After change is in effect do not run MagPick while changing magpick ini user should be able to use Russian fonts in the screen annotations such as text color scales etc However this will not affect Postscript or PDF output 22 7 2 PostScript and PDF fonts MagPick handles Russian text by re coding it into KOI 8 therefore to enable Russian text KOI 8 fonts should be added to the Ghostscript distribution For more information on KOI 8 fonts please check http www 1biblio org serge1 Software postscript html Follow instructions and download the following files ftp metalab unc edu pub academic russian studies Software PS CyrPS tar gz ftp metalab unc edu pub academic russian studies Software PS CyrPS afm tar gz It was noted noted that fonts could have different names and user needs to unzip them manually into fonts folder User also needs to add new font names to Fontmap GS file by hand After this editing part of the Fontmap GS file would look like that 8This recipe has been checked with US versions of MS Windows 19Most modern systems use Unicode 187 Target position export Now t
152. ce if most of the turns are 180 and some of them just 90 or less latter may not be removed automatically If there are only a few turns in the area manual removal could be a better method Automatic turn removal is available under Profiles Remove turns menu Control dialog is shown on figure 30 Dialog parameters are the same as it shown on figure 30 1 Turn leg distance m Distances AB and BC on figure 29 2 Max turning angle deg Angle o from figure 29 If angle is less than this value points A B C are accepted as a turn gt 3 Min parallel angle Maximum allowed angle between vectors AA and CC If angle is greater that this value points A and C4 stop moving toward point B 4 Use coordinates for channel Coordinate of what channel to use for multi sensor arrays always 1 for single magnetometer unit 5 Split data into lines based on turns Assign new line number after each turn 65 Profile data transformations Automatic turn removal x Turn leg distance m 100 Max turning angle deg 120 Min parallel angle deg Fo Use coordinates for channel fi M Split data into lines based on turns Save into the file 02_1 7 OF Survey 02 17 0O7 splitdat MV Load data upon completition Warning This unloads current profiles Ok Cancel Figure 30 Automatic turn removal control dialog 6 Save into the file After turns are removed the result is saved
153. check UTM calculator is provided to convert Lon Lat coordinates into Northing and Easting and vise versa Knowledge of the central meridian or zone number is one of the problems using the UTM system Six degree zones start at 180W and go to 180E MagPick could find zone and central meridian based on data The following shows how to proceed e Check Set central meridian from first sample e Go to UTM calculator and enter Latitude and Longitude of your location e Press Lon Lat gt UTM Read Northing Easting UTM zone and central meridian The central meridian value in the main UTM setup dialog is updated automatically 109 Geographic projection transformations UTM and PROJ Allows you to save and load projection parameters from file Set of ellipsoid names to choose Itis recommended to keep this from Major axis and flattening are file with the data changed when you change ellipsoid to reflect your choice UTM Gauss Kruger transformation setup i xj r Ellipsoid parameters Ellipsoid name WYGS 84 1984 Major axis m Ellipsoid s parameters If you choose User defined you can enter these values If checked central meridian will be taken from first Lat Lon sample UTM calculator will show zone and C M Warning if you do inverse transform only do not check this box Flattening aa parameters Base projection parameters central meri
154. ck Export picks gt DXF Bitmap GeoTIFF Postscript Exit Google Earth Close Close All Recent Files gt Figure 119 Calling Google Earth export menu A detailed description of the controls are listed here 120 1 Elements to export This is list of available picture parts layers This may be changed in the future MagPick versions Each layer is represented by a separate folder under GE and can be individually enabled or disabled within GE MagPick layers selected for export are marked with an asterisk Each layer has its individual properties which can be accessed by clicking the Properties button or by double clicking on the layer description Mark All Unmark All For convenience all entries can be enabled or disabled for export at once using these buttons Note that if all layers are disabled no export occurs the Ok button will be grayed out Properties This button allows editing of a particular layer Google Earth Folder Name This is name of the root folder under GE just below GE folder with KMZ file name Apply inverse UTM Because MagPick operates with UTM coordinates and GE operates with Latitude and Longitude an inverse coordinate transformation must be applied for proper geo reference This means that in most cases this box will be checked unless the user loaded raw Lat Lon in MagPick Note that the default GE datum is WGS84 therefore coordinates in Ma
155. ck using short UTM coordinates It is also possible to prepare maps in UTM however this is not our final goal At some points we need to save data in the format acceptable byCorpscon Unfortunately Corpscon does not use negative values for Longitude in the Western Hemisphere It uses positive values because it was developed for the U S and this country is located entirely in Western Hemisphere or use Latitude Longitude postfixes such as N and W MagPick has a new option to save and load the data in this format The typical MagPick profile saving dialog is presented on figure Here are the following conditions that should be met to create a Coprscon compatible data file 1 Coordinates should be saved as Lon Lat Proper UTM parameters should be set they are typi cally set if data is loaded as Lat Lon with UTM transformation on the fly 2 Append Lat Lon postfix should be checked For instance this means that for instance 90 West are saved as 90W and not as 90 3 User can check Create list file to load data but this will only work with saved data not data transformed by Coprscon Simple load menu should be used to load converted by Corpscon data 22This section was inspered and heavily contributed by Eric Fischer Marine Surveys http silvettigroup com 208 Coordinate transformation using Corpscon software Save profile data x What to save All pro les gt How to save asxyz x Line numbers Simple line
156. column in data file Typically 2 for marine G 882 881 Add calls file selection dialog and shows this dialog Add channel allows to select 2nd 3rd etc channel from the same fil Set which samples to load each each 2nd 3d 5th etc Fie you are working with now Create profile description Name test 1 01 02 07 Survey INTERPOLATOR INT ny v Select splitting mode No split lar 17 LINE z 2 omer ir split by distance or split by line eee LINE Disens 10 00 0 Enter Distance if you are using z 13 Lon wz 7 14 Lar_me y a maci y split by distance J Xx 113 LON_M Y 14 LAT_M2 Data 1 MAG1 olas wiere are you Depth g DEPTH1 Alt fa ALTITUDE TE EIE X Y and field If file has header cr altitude r avallabIe A M Use time Time fe TIME y Date B DATE y it is displayed f z p J Date format Date and time if available Active color RED X mmay y Inactive color BLUE y If Auto short UTM is selected Set color names for active and UTM setup dialog is called automatically inactive profiles j Apply UTM on input positions in Lon Lat METIA capa med UTM parameters Calls UTM setup dialog Ok Cancel Important If position is in Latitude and Longitude they should be projected using short UTM Use Auto short UTM for projection parameters Figure
157. culate Isolines intervals won t be 5 Press this button to id updated till you press it C pi you p J Fast drawing no labels available 9 Uses fast method to D 41 Places after dot for annotations contour data but without label F J7 Label contour Decimals _0 Distance between labels map units 130 00 10 Enables contour annotations only for C slow drawing J below it may be about 30 m Text 12Space for annotation For oe L is scaled to fit into this gap Label length map units wi 13 Controls contour labeling Distance along the contour to insert label gt For example if you area is 1000 x 1000 m you may wich set it as 200m J These items have no effectif Automatic is checked Figure 4 Isoline parameters dialog box Interval Interval between contours Data levels are distributed uniformly between Min and Max with this interval Calculate After you entered Min Max Interval their values have no effect till you press Calculate Program calculates new levels you can see them in list box Contours Isolines Current list of levels for contour plot It can be calculated or loaded from file Read from file If you use custom selection of the levels you have to prepare ASCII file with desired values Only the first column of such a file will be read rest of the string is not significant Results are displayed in the Contours Color The default con
158. d depth zZ De gt Do Do gt n sea bottom TVG position in water column Estimated pipe line depth Smoothed pipe line depth A a water depth meters Vertical datum NAVD 88 SOBNAATARWONAOOMNAMAWNBOAN Nara da E kc 1 f i 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 distance along pipe line meters o Figure 111 Typical result of Magnetic Field data interpretation Raw depth locations are shown in blue Averaged depth is shown in magenta It can be seen that depth profile repeats bathymetry it also can be seen that pipe line is visible on the banks of the navigation channel which was verified with acoustic methods Data courtesy to Environmental Solution San Rafael CA The rule of thumb is that individual depth estimates cannot be trusted There should be sufficient number of intersections say 10 and above to estimate burial depth MagPick offers two empirical pipe line processing techniques based on observed Total Field and based on computed Analytic or Quasi Analytic signal Both methods treats profile data intersection by intersection and therefore both need their results averaged at the end The data processing flow is similar to HVDC cable in both cases 161 Pipeline data treatment 21 2 Approximation formulas The following empirical formulas are used to approximate data 1 For Analytic or Quasi Analytic signal A ran bale 0 b xo Aa Here J xp z 5
159. d into planar co ordinate system and then back to Lat Lon on export This chapter describes how to deal with case 2 which covers almost any land marine or air borne magnetometer survey 106 Geographic projection transformations UTM and PROJ Figure 70 shows coordinate transformation flow in MagPick Original data recorded in Lat Lon are projected during reading of the profiles recorded in the field they are presented as planar during data processing Planar data can be saved loaded from intermediate files including MagPick project file The processing results including modified profile data and target worksheets can be saved in latitude and longitude 12 2 Coordinate systems in MagPick details Planar coordinates are typically expressed as distances from some known point such as geographical equator or prime meridian For instance UTM coordinates of the point 125W 37N are Northing 4096742 06 m Easting 322037 81 m First number is the distance from the equator second number is the distance from the central meridian of the UTM zone 123W in this case plus 500 000 meters To reduce memory consumption and general PC overhead MagPick stores these values as single precision 4 bytes floats Therefore substantial round off error occurs if data is treated without appropriate False Northing and False Easting In this example round off error for Northing is 2 meters or 5 x 10 of the value To avoid these errors appropriate
160. data grid and profile clipping using the polygon as well as constraining data for profile based magnetic inversion Polygon can be dragged as a whole or individual vertices can be adjusted 206 Map annotations 25 1 6 Profile Stack Annotation G Profile stack annotation is useful when stack plot is used It is available from Add stack scale menu Its properties dialog box is shown here figure 154 Stack scale propretries x MV Fill with solid color Fill color E M Draw border Border colar K Pen width pix lo AE RON Al Font size 70 1 4 J 432 Stack amplitude field units 100 Annotation text nr Layout EAT Ok Cancel Figure 154 Stack profile annotation properties dialog This dialog is pretty similar to the sample annotation label properties In addition it has am plitude in field units annotation text and layout Layout can be vertical or horizontal Stack scale is always drawn as simple sine wave of user defined amplitude Depending on fill option int th stack menu Options Settings Show profiles dialog negative or positive part of the sine wave is shaded It uses the same color as the stack plot 207 Coordinate transformation using Corpscon software 26 Coordinate transformation using Corpscon software 26 1 Disclaimer Use the following material on your own risk The procedure below is one of the possible ways coordinate conversions Please ve
161. dated showing the smoothing result e If you are not satisfied with the result you can repeat the smoothing again The result of the previous operation is discarded e If you are satisfied then you can replace the original values with smoothed values by selecting File Accept menu There are four choices here you can replace all profiles only active profile you can take just the smoothing result or the difference original data minus the smoothed data e If for some reason you want do discard the smoothed curve go to Edit Discard menu The smoothed curve will be erased e After you smooth data and replaced original data you should save the profile data or results will be lost after you exit the program If you saved data with smoothed curve still on the screen then there is an additional column in the file called T_calc This is result of the smoothing 7 2 4 Linear data transformation Data smoothing represents a type of advanced transformation However MagPick has a simpler abil ity linear data transformation Every profile reading can be transformed with the linear formula Trew ax Toia b Here Toia denotes the original profile reading a is the scale and b is the bias of transformation Tnew is the transformed field value The function can be applied to all data to active profiles or to the part of an active profile between markers It might be useful when the data needs to be calibrated with a known coefficients or when some
162. dian latitude of origin and scale factor Central meridian degrees 123 Central latitude degrees 0 00000000 Scale factor 0 9996 for UTM 0 999600 False Northing m 0 00 j False Easting m 0 00 Note Northina and Eastina are added to transformed values Load from file Save to file UTM calculator Rotation Use other projections advanced Ok Cancel False northing and easting to be added Note that if you want to cut coordinates these values should be negative UTM calculato xj r Geodetic Longtitude 125 LL Latitude Br call Lon Lat format decimal degrees this UTM Gauss Kruger Northing 4096742 06 Easting 322037 61 Enter Lat Lon of the point to be projected here Follow format specification for example if F Ada 10 000 000 m to the Northing format deg min sec enter 3 numbers separated i for Southtern hemisphere by spaces or read here result of UTM gt Lon Lat Lon Lat gt UTM UTM gt Lon Lat Read UTM coordinates or enter UTM to be transformed in meters here For inverse transformation make sure that central meridian is correct This invokes particular forward or inverse projection Figure 73 Built in UTM setup dialog in MagPick Note that the UTM calculator is a modaless dialog box and user can do changes in
163. directions and produced map is not very informative To proceed with the leveling activate map grid window and go to Profiles Level using tie lines menu The leveling dialog is shown on figure 56 The following fields need to be set 1 Channel to use For multi channel data set select channel to be used for leveling computations Results are applied to the rest of the channels when computation is complete 2 Time variable Possible selections are Fiducial or Time if available Use Fiducial unless you are loaded profile data with time stamps 3 Solution type Possible values are Least Squares L2 or Median L1 Latter delivers better result but more time consuming However it is not so slow as in case of spatial trend removal because number of equations are much smaller Note that for linear trend removal as part leveling L2 is always used anyway 4 Speed up distance meters This is important optimization parameter which greatly reduces computing time The most time consuming operation is intersection search This parameter allows program to decimate profile data in this example go with 20 m intervals in place of real sample interval which can be very small and search for approximate location of intersections When found precise location location is re estimated using actual data sample rate Value of 20 m is sufficient in most cases 90 Leveling tie lines Profile data leveling with tie lines Channel to
164. distance behind the ship on the line New point M is the estimated position of the fish time t It can happen that distance BM is greater than BN if ship does a sharp turn In that case the position of the fish is not changed literally fish should sink in this case These calculations are repeated for each GPS point Method explained above assumes that the fish position at time fo is known but in general we do not know this Therefore to start the calculation process we need to find the initial fish position Different techniques might be employed for locating the position The easiest one follows use the initial part of the recorded path to find direction of motion by approximating these positions with a stright line using the least squares method and count the cable length along this line This gives a reasonable estimation for the initial fish position When the initial position is selected the dragging method can be used After short distance influence of initial position becomes negligible Potential problems It should be noted that this method is not designed to work with sharp turns It does not take into account the depth of the fish if fish is deep then horizontal distance is less than the total cable length Another problem is that the GPS normally is not mounted at the same point where tow winch is therefore the effective cable length should include distance thr GPS to winch offset Simple geometry calculations should be used to est
165. drawn on the same side of the XY line Choose Fill type positive and fill color you like Say green e Do not check Clip stack plot for now This feature allows clipping values on the stack plot which are bigger or less then certain limits Press Ok and to close dialog and then close Common parameters too You can see now a map overlaid with the stack plot Do it one more time filling in negative anomalies To see the stack profile plot better you may want to get rid of the color map To do so Op tions Settings and uncheck Color map Press Ok 224 Tutorial This raises an interesting question In some cases you are not able to produce a quality magnetic map but still want to operate with profiles This means we need the views we discussed in this section The background for these views is the map To resolve this situation MagPick creates a fake map to serve as a background which is never displayed For instance you could load profile data without loading the map Then go to File New and select Grid MagPick shows positions of the profiles using dummy map Alternatively you could load any other map to serve as a background It is common to load bathymetry map in marine surveys and display stack profiles on top of it Advanced feature how to add something on top of magnetic map In many cases we need to see some geometrical topographical information on top of the magnetic field This paragraph is a hint how you can do it
166. e Northing and Easting This approach is much more flexible that built in UTM function because it enables user to easily transfer data from different coordinate systems For instance latitude longitude NAD83 data could be loaded into MagPick and transferred into UTM meters work is performed in MagPick modified profile data could be then saved as State Plane NAD27 data in feet There are two most important projection strings in the PROJ dialog 1 External or from or longitude latitude string This is projection of the input data it corre sponds to the top and bottom blocks of figure This is projection used to load raw data and export data from MagPick 2 Internal or to or UTM State Plane etc and false Northing and Easting This projection is used to present data in MagPick compute distances do inversions etc It corresponds to the middle part of figure 70 112 Geographic projection transformations UTM and PROJ Advanced Projection Parameters x L Field data projection use PROJ string parameters from proj latlong datum W4GS584 Set default ERSUN MagPick data projection to init epsg 2801 Match UTM EPSG False Northing 140000 000 Set offsets from data False Easting 1180000 000 A Calculator From To O allt ME lt ME Degree format Decimal degrees y Ok Cancel Figure 76 Setting projection parameters in MagPick using PROJ Most important con
167. e algorithm It allows the user to control interpolation using the tension pa rameter ranging between 0 and 1 Tension set to zero gives a pure minimum curvature solution which can have undesirable oscillations Tension set to one delivers a harmonic solution no maximum and minimum except data points Tension equal 0 25 is used to reduce oscillations and generally recom mended for potential fields such as gravity or magnetic The value of 0 35 is for steep topographic data The method also allows the user to constrain a solution with fixed values interpolated data points can not be out of pre defined range or with data minimum and maximum values An unconstrained solution is also possible The method is iterative and convergence limit and total number of iterations can be entered The program stops iterations when the maximum absolute change in any grid node is less than the convergence limit The program also will stop if the total number of iterations is exceeded 53 Grid operations 6 2 Save grid There is no need to save a grid created by MagPick because it gets saved during its creation However MagPick provides a set of operations on existing grids After each operation has been used the result should be saved into a file First if you wish to keep any change you did with a grid you should save it Go to File Save and pick the file name you want to use Then MagPick asks about the format for the grid file There are three pos
168. e borders Change data color mapping Go to Common parameters again Here we will learn how to change the color scale The Autoscale box is checked now The two grayed numbers above it are minimum and maxi mum values of your data Uncheck it The fields above become available Set the minimum to 1500 and maximum to 2000 All the colored range now is mapped to 1500 2500 and you can see only the top of the moun tain All that is less then 1500 is mapped with blue All that is more that 2500 is mapped with red Intermediate colors are in between blue and red Now lets look at another kind of mapping Say we set range 0 500 All what above is or below this range will be wrapped to this range Therefore the value 510 will appear as 10 and value 1010 too This method is useful for viewing of magnetic maps which have some points with extremely high values MagPick employs this method using the Wrap color scale check box Set minimum value as 0 and maximum as 500 check the box press Ok and see what happens 216 Tutorial It looks now as a rainbow The data going up in color changes from blue to red When it reaches 500 it becomes blue again and so on Now uncheck this box and check Autoscale again Color palette MagPick implements two methods of color mapping linear and gradient Linear means that the color range simply gets mapped to your data range There are 41 pre defined palettes in MagPick To see them all go
169. e dialog MagPick prompts if user wants to accept these false Nor thing and Easting in place of false Northing and Easting of UTM transformation The question dialog is shown on figure 160 Answering Yes has some advantages First of all user can display mouse and target positions in full State Plane coordinates Second Postcript PDF output can be prepared with coordinate grid annotated in State Plane GeoTIFF export can be prepared in State Plane Coordinates as well If answer is No all the above can be enabled by going into UTM dialog and setting false Northing and Easting to the same as above see figures and 159 It s important to understand that in this special case all what is used of UTM parameters are false Northing and Easting After profile loading is finished number of profiles should be same as before coordinate trans formation Create a new grid window menu File New Grid view and make sire it looks correct Errors will not likely be subtle here Perhaps an X and Y have been transposed and it will be fixed 212 Coordinate transformation using Corpscon software Load X Y Data profiles y x Add Delete Delete all Eea Ea Add channel Note false Easting and Northing are to be added to your positions Filter by signal Signal column fo Signal level 200 Ok Cancel Figure 159 Loading profile State Plane data with false Easting and Northing Question use short coordinates xi p Would you li
170. e diff grd You have done well The magnetic source a very dangerous one in this case was located The real position was X 8 5m Y 10m and Z 2m Compare these values with X Y Z in the worksheet on your screen Stability of the solution We were able to find magnetic source but how stable is this solution What should be the criteria to accept it or not Basically there are two types of criteria e What is the difference between the observed and calculated field Which features of the observed field we can see as well the in calculated one What is numerical difference These are the questions which should be answered Therefore it is important to inspect the observed and calculated fields e How stable is the solution What happens if you completely change the initial location and depth of the source Do you still get similar numbers You should investigate this empirically Here are five attempts with a completely different initial position and depth of the source see figure 162 Table 2 shows initial depth of the source and estimated X Y Z locations You can manipulate this data testing the results Delete your pick change mode to Simple pick make the pick somewhere else Then start the inversion Change initial depth as well You will find that this estimation is pretty stable Of course there are some ways to confuse MagPick on this data for example set the initial depth as zero 229 Tutorial Inital depth 1 m Inita
171. e final message Files created by gnuplot have names 193 Anomaly plots with gnuplot 4 Magnetic map picking patch1_tf_as_map File Edit View Window New Open Save gt Close 02 77 0 50 7 52 7 09 7 60 3 47 7 56 14 97 51 02 2 60 2 71 0 49 59 85 0 62 77 68 0 49 18 87 1 64 MAMAN aan Projects Export Create protocol Plot inversion graphs Exit Recent Files Figure 139 Inversion graphs menu similar to ID_1__02_09_12__14_31_29_1 png where keyword ID follows by ID number from the dipole worksheet and name of the corresponding protocol file After process is successfully completed program shows final message with total target plots re quested and total created sed141 If some protocol files cannot be found number of created plots is less then requested In case if no output is created plese check if Inversion folder points to correct location for particular project The plot itself looks like the example on figure 142 Horizontal axis of the graph represent distance assuming uniform speed across the area In case of multiple channels such as TVG channel 1 position is used Horizontal axis is centered around the data point closest to the estimated target location 2Inversion folder is not part of the project file and has to be maintained by the user 194 Anomaly plots with gnuplot Create inversion plots C Program Files gnuplot
172. e for canvas to work in the Google Earth There is no need to specify js folder for PNG format Note that KMZ files with Java script content may mot be saved correctly from Google Earth therefore in some cases to combine data inside Google Earth user should de compress KMZ and induce content manually 198 Map annotations 25 Map presentation elements Beginning with version 2 8 MagPick introduced some standard map annotations Those are floats user defined objects which can be moved anywhere within the borders of the grid display User can select this object by clicking on it access object menu by right clicking on the object or access object properties dialog by double clicking User can delete object by pressing Delete key while object is selected To place annotation elements it s certainly makes sense to assign sufficient margins for the plot Options Size menu All available annotation types can be reached using map context menu Press right mouse key then go to Add menu as it is shown on figure 145 Edit Redraw Select Simple pick Rectangular pick Delete pick Zoom Direction Pick profile marker Add coor scale Add annotation Add polygon Add map scale Add stack scale Add north arrow Add all frame annotations Edit All Figure 145 Annotations context menu Each of the individual types can be reached by selecting corresponding menu After menu is selected mouse cursor changes
173. e ground No further coordinate transformation is needed for that type of positioning However user should be aware of orientation of the local coordinate system relatively to geographic North many operations such as an inversion reduction to the pole etc require angle between local coordinate X axis and direction the the North 2 Modern case Data is recorded using Latitude Longitude most likely with GPS That type of positioning cannot be used directly in MagPick and must be projected into plane using cartographic projection Examples of these projection are coordinate systems used as standards in different countries such as UTM Universe Transverse Mercator Gauss Kruger variant of Transverse Mercator State Plane in USA and other systems If user does not know or does not have specific projection requirements MagPick selects appropriate coordinate system automatically Survey profile data recorded Latitude Longitude MagPick reads data and projects into planar coordinates on the fly possibly with datum transformation Intermediate results Profiles target positions maps magpick project files in the projected coordinate system Output results Proofiles in Latitude Longitude Geotiff files DXF files in planar coordinate system PDF outputs to scale with Lat Lon grid Figure 70 MagPick coordinate transformation data flow Lat Lon data are projecte
174. e map view menu Edit Pick profile Activate this menu item move the mouse cursor to some profile and click left button Profile is deactivated or activated and therefore all subsets disappear from profile view window If Browser dialog box is opened list selection is altered too Depending on on discretization interval along the profile number of data points used in the pro file inversion could considerably exceed number of data points used for map based inversion Therefore the time of computation might increase 131 Estimation of magnetic sources 3 Instead of relative depth real depth is used This means each point of profile involved in the inversion is taken with its z coordinate It allows usage of the data obtained at different elevations With other side it means that all z values are measured relatively to some pre defined system In the case of GPS heights they are geodetic elevations 4 Because of the above reasons the initial depth of the source has to be specified carefully to avoid choosing it above the data 5 In some cases the Z values have considerable noise and can not be used directly for interpreta tion In such a case smoothing of elevations is required To start a profile based inversion a set of profiles have to be loaded into the program see above Then the interpreter can view the magnetic maps if available or browse profiles as T dist graphs The aim is visual selection of potential place
175. e oe eS 174 Sar ated ue E Hae Hat eee 175 reeset er ere 175 oe oe ee Roe Ree ene nee Res 176 pa Suse Reimer es ee eS ee es e ee seo eS 177 o ata amp ghey ee a cela eee oe Se a 177 22 4 1 Saving profile windows into TIFF o o e 181 22 5 Preparing printouts via Postscript o e ee 181 O AR eee ee 182 OA A AA a ee wh ele gee ee a 184 AA e o a E oe 184 22 6 2 Converting PS file to PDH os cp ba ee eee ee eR eR ER 184 E Se Fa LE OS Ee Pee Be Oe PR 184 Ae dais eh Cente ee 186 Coe wee Eee od ee Bree iek mae OR ee Oe we G 186 22 7 Using Cyrillic Russian text in MagPick o o 187 22 1 1 Screen tom 640 ha ek a ok ee S eR AGREE AAA 187 Lah Re e SHES ERE ESTER A 187 188 a Soke bag aa ins EA Gon as a a 188 192 24 1 Download and install Gnuplot o o 0020000008 192 os 192 e Beda ara e tk 192 ie a ir er e 197 25 Map presentation elements 25 1 Individual annotation types ee ee 25 1 1 Text annotation label A H a 25 1 2 Color Scale B sv sos sec a io a a de e a de 25 1 3 North Arrow Chloe ai amp e 2 S68 Se a 25 1 4 Map scale D ra a bom Se ARA RARA 25 13 POZON E irse AAA 25 1 6 Profile Stack Annotation G ooa ee 26 Coordinate transformation using Corpscon software 26 1 Disclaimer ca sea aa ee a atr a Ee a a a 26 2 Procedure outline o ooa aa a a a a a a a 26 3 Preparing data
176. e taken as an approximation of the root It is clear that negative roots do not have physical meaning 0Here and below multiplier 10 is included into Jiem 137 Implementation of inversion It has to be made clear that this approach does not provide a good mass estimation for all cases This is due to possible large variations in the magnetic properties of the different metalic objects In the case of two positive roots no assumption can be made which one is correct 17 5 2D inversion Full 3D inversion requires multiple profile space separated lines or grid points distributed in the target area as well as known parameters of the Earth s magnetic field If all this information is available MagPick can estimate spatial location and magnetic moment of the dipole target Special case of inversion is 2D inversion when only one line of data is available Assuming data measurements are distributed along the straight line one can see that this line and target location point define 2D plane The illustration is presented on figure 87 Here 1 is possible target position which together with survey line defines plane marked as 2D inversion plane XOZ on the picture water surface water surface DS Vey y E Klis 72 T x ro AR E Es g line o N D offse g T N a SE ba Figure 87 2D inversion in the plane created by survey line and target location shown in gray Absolute location of XOZ plane is not kno
177. ection in which the profile was taken by arrows each 200 pixels along the line The direction is defined by the data order in the original file and therefore will be opposite to the real direction in the case of G 858 data because this device reverses order of magnetic readings e Check Plot stack profiles This means you want the feature added to the map e Set Datasets to draw I In many cases it will be 1 so do not change this value e Set Data scale 100 MagPick has to transfer data values to position values to plot stack profiles and therefore it has to scale data values To do this MagPick divides data values to the number you have just entered To increase the span of the anomalies on the final plot you decrease this number and vise versa For example 50 will increase anomaly span 2 times Select Type as Fixed direction This means that positive anomalies will be drawn to the direction specified clock wise Enter 90 degrees as Fixed direction azimuth Other choices are End points and Normal to path End points selection means that two end points of each line are used to calculate the stack profile azimuth Normal to path selection means that at every point the stack profile plot is perpendicular to the path Preferred direction is the azimuth to where positive parts of the anomalies will gravitate This is useful when you have parallel lines taken in two opposite directions and you want the positive part of the anomaly to be
178. ection name see PROJ manual for full list south Denotes southern hemisphere UTM zone towgs84 3 or 7 term datum transform parameters x0 False easting y0 False northing Note that false Northing and Easting are set separately in MagPick zone UTM zone 13 units Map units Most used are m meters us ft US survey foot ft international foot km kilometer Please consult PROJ manual for more details 12 6 3 Example Louisiana South NAD 27 in US survey foot Input data ordinary GPS in WGS84 from statement proj latlong datum WGS84 Output data NAD27 EPSG code 26782 US survey foot to statement init epsg 26782 Note that this includes datum to datum transformation WGS84 to NAD27 already defined in proj EPSG file as datum NAD27 Control point 90W 30N gt Easting 2422064 42 Northing 487240 82 us ft Note the same result can be obtained with init nad27 1702 units us ft Note that 1702 is Corpscon projection code for Louisiana South 118 Geographic projection transformations UTM and PROJ 12 6 4 California Zone 2 NAD 83 in US survey foot Input data ordinary GPS in WGS84 from statement proj latlong datum WGS84 Output data NAD27 EPSG code 2226 US survey foot to statement init epsg 2226 Note that this includes datum to datum transformation WGS84 to NAD27 already defined in proj EPSG file as daatum NAD27 Control point 122W 37 6N Easting 6
179. ed program auto matically chooses these values based on data Because X axis can represent different variables i e X Y distance along profile projection be careful in choosing them When you change the type of axis box 3 is automatically checked and new limits appear 3 Data limits If these checkboxes are checked data limits always will be taken 4 Type of X axis Depending on where you created profile view there are two to four choices here a X Y profile inversion view created from map view without additional axis b Along profile X Y profile view created from map view without additional axis c Along profile X Y Along pointer profile view created from map view with additional axis In this case the direction of axis is fixed after creation of profile view even you have changed it on the map view profile view will still operate with an old one This happens because the profile view is actually an independed window opposite to profile inversion view d X Y Along pointer the profile inversion view which is a child of the map view with an additional axis direction In this case if you change the pointer direction the profile graphs are updated automatically 5 Shrink to canvas It sets the method to shrink to canvas see above If this is on then the fields in 8 are unaccessible if not checked then the fields in 7 are inactive 48 Basic operation of MagPick 6 Grids Here you can specify the coordinate m
180. ed along the polyline used for initial approximation ii Active profile The same as above but only one active profile is used iii Active between marks Only active profile is used and user must use marks to limit data for approximation b Polyline name Name of the polyline used to approximate initial location Note that there could be multiple polylines on the grid view but only one is used c Data type Can be Analytic signal for bell type approximation or Total field for dipole monopole curves combination d Use data window Check this box and specify data window in meters Data window is centered at polyline and survey line intersection and it is counted from that point Thus entering 100 m means that program uses part of the profile centered at an intersec tion and extending by 200 m total e Channel for inversion In case of multi channel data only one can be used at a time Specify it here 2 Half width level a The level of the anomaly used to find object depth Because method is empirical this value could be adjusted based on ground truth known at some points It appeared that 50 is most suitable for Analytic Signal and 33 for Total field User may need to adjust this value based on experience b How to report depth Selections are from the sea floor from sea surface and from the sensor Note that altimeter and depth sensor are required to report from the sea floor and depth sensor is
181. egments where the field is above or below middle line For each segment it calculates extremum point If extremum value is more than the user set limit MagPick draws a dimension line with annotation This can be a value above the middle line relative or an absolute value or both However if there is not enough space to accommodate the label it won t be printed The user can disable this feature by unchecking the box Use stack plot labels to select labeling threshold set type of annotation its color text hight and label suffix see figure 8 THe latest Magpick versions provide considerable improvements in map viewing It includes two new kinds of data mapping Shaded relief and Color illuminated map Both involve some simple shading calculations which the make map naev a better contrast To use them click on Color map check box in Common parameters dialog box You may need to click twice to call Color map draw mode dialog Here you have next choices see figure P 1 Drawing mode Choose the type of the map you want to draw The possible choices are 3Magpick calculates average or linear approximation for each profile line separately It leads to the breaks in the stack plot if continuous line was divided to the set of sub lines 27 Basic operation of MagPick Stack profile labeling 6010 6020 6030 6040 6050 6060 6070 6080 6090 6100 A a E eco ee le ami AA ee gt 2900 2900 Y m 2890 2890 2880 2880 2870
182. eld liable for any damages arising from the use of this software Permission is granted to anyone to use this software for any purpose including commercial ap plications and to alter it and redistribute it freely subject to the following restrictions e The origin of this software must not be misrepresented you must not claim that you wrote the original software If you use this software in a product an acknowledgment in the product documentation would be appreciated but is not required e Altered source versions must be plainly marked as such and must not be misrepresented as being the original software e This notice may not be removed or altered from any source distribution Jean loup Gailly jloup gzip org Mark Adler madler alumni caltech edu 1 8 LIB TIFF Copyright notice Copyright c 1988 1997 Sam Leffler Copyright c 1991 1997 Silicon Graphics Inc Permission to use copy modify distribute and sell this software and its documentation for any purpose is hereby granted without fee provided that i the above copyright notices and this permis sion notice appear in all copies of the software and related documentation and ii the names of Sam Leffler and Silicon Graphics may not be used in any advertising or publicity relating to the software without the specific prior written permission of Sam Leffler and Silicon Graphics THE SOFTWARE IS PROVIDED AS IS AND WITHOUT WARRANTY OF ANY KIND EXPRESS IMPLIED OR OTHERWI
183. entation The simplest way to calculate the average value for the profile and subtract it from the field thus producing positive and negative anomalies However this method would lead to unacceptable results if field has a regional trend For example a slow increase from West to East see figure 6 Plate a shows a magnetic field as distance along the profile or time There are few anomalies with a linear increasing background Plate b shows what one can get if a 26 Basic operation of MagPick a Field graph as function of distance or time D o o averagevalue fe 2 e 3 SON od Are E pe ron eee ax 2 we distance along profile or time 4 b Stack plot with average middle line Northing profile position 7 Easting c Stack plot with linear middle line Northing N SS DA profile position Easting Figure 6 Different methods of creating stack profile plot simple average is used A better way is use the linear approximation for the background as in the example on plate c 14 Stack labels After a stack plot map is plotted it might be difficult to find what the anomaly values were To make it easy magpick can automatically draw dimension lines on minimum and maximum points Press this button to call the stack labels dialog and set the parameters of this feature See figure 7 for an example of stack labeling To label a stack plot MagPick searches for s
184. eous result Data can be projected back while saving or target coordinates can be expressed in Lat Lon Below is typical schedule for marine magnetometer data recorded as Latitude and Longitude 1 Use Apply UTM on input drop down list to select Auto Short UTM Program will analyze beginning of the data file and find best UTM parameters for MagPick To confirm it displays UTM setup dialog see page 42 Basic operation of MagPick 2 Check parameters selected by the program and save them as a file This file has extension utm can should be kept with the data to allow later conversion back into Latitude and Longitude UTM parameters also saved into profile list file if one is created 3 If multiple data sets are loaded auto Short UTM should be used only for the first one to avoid different projection parameters for different data sets For the rest of the data use Manual UTM and select proper UTM parameters In most cases you can just re load UTM file you have just saved 4 Press OK to close UTM setup dialog Program is ready to load Lat Lon positions e Now press OK to complete profile description procedure You have just created description for one data set channel If this is all what you need you can press Add button again and proceed with another data file e If data were acquired with a multi sensor array then other channels should be loaded This can be done by hand by editing profile list file MagPick prior ve
185. equence of operation is the following 1 Prepare PDF file of your map with GSView as described in the previous section 2 Convert PDF file into EPS with the command pdftops eps input pdf output eps where input pdf and output eps names should be replaced with actual file names Note that resulting output file can be very large 3 Add TIFF preview to the EPS file with the command epstool add tiff6p preview bbox output eps outputl eps where output eps is the file created in step 2 and outputl eps is a new filename This command will add low quality bitmap preview to the EPS file The purposes of the preview are to allow MS Word or Open Office to display the picture while you edit the document However the quality of such a preview is low and will remain low until you print document to the PDF or Postscript printer 4 Include EPS file into MS Office or Open Office the same way as you would insert any other picture file output1 eps in the above example For MS Office an additional input filter may be needed Note that both word processing applications show TIFF preview and not the actual file Scale the picture as required to fit the page Scaling will not reduce resolution of the picture in the final PDF file however do not expect high quality output until the whole document has been converted to PDF The most convenient way to convert to PDF is using Free PDF or CutePDF writers We found that at least for version 3 0 Open Office
186. er of readings in the input file taken along profile 4 Profile plot parameters 1 Show direction of profile with sign gt TA 2 Interval between signs gt Distance is 4 Each profile file can have multiple datasets Here you can define which one you wish to plot as stack for simple load it should be always 1 3 Request to draw stack profile plot a oer TERO Show profile direction each 20 pixels gt 20 To plot stack we E Plot stack profiles Datasets to draw 1 x need to convert field values into I Data scale 5 0000 Preferred direction 90 00 Type End points Fixed direction azimuth 45 00 6 Positive sides of the plot will gravitate to that direction unless Use fixed direction distance Data gets divided by that value A Fill type Positive IS checked 7 Request to use clockwise from north fixed direction Clip stack plot Max 43300 0000 for positive parts g Fixed direction azimuth of the data clockwise from north Ok Cancel 9 Which part of plot to fill 10 Choose fill color here 13 Middle line approximation 12 Clip range to produce stack plot simple average or linear by least squares of clip range are cut drawn as and set their parameters 11 If checked all data values out 4 Enable stack annotations flat lines Figure 5 Stack pr
187. er should inspect profile plots to see how approximation fits the field Here 1 13 is an example for Quasi Analytic signal approximation Poorly approximated intersections should be removed 6694 6696 6698 6700 6702 6704 6706 6708 6710 6712 6714 A A A AAA ee aa as 5 biases The dO ls er re AN cc DADA 6694 6696 6698 6700 6702 6704 6706 6708 6710 6712 6714 Bi Figure 113 Quasi Analytic signal approximation The solid line is original data the dashed line is an approximation The dashed line is used to estimate position of the maximum and width at certain level of the anomaly which is proportional to the depth The cross shows estimated XY location MagPick currently does not provide tools for averaging pipeline depth One can use Excel spread sheet or other tools for that 164 Export and printing 22 Export to the CAD Google Earth printing bitmap formats and including into MS Word and OpenOffice 22 1 Export to the AutoCAD TM and compatible software via DXF file Magpick is capable of preparinf an ASCII DXF file which can include the following elements e Coordinate grid with axis annotation and general title The default font is used and the grid steps are the same as on the screen Grid labels can be formated in meters or in degrees minutes and seconds Magnetic field contour map as lines contour plot option The slow contour method is rec ommended because it allows inclusion of labels However the fast co
188. eractively and therefore deselect them in the Profile Browser list This way you remove all subsets from the screen To remove just only part of them use Profile Browser dialog 5 6 Latitude and Longitude coordinate grid If UTM transformation see below 13 is used it is possible to plot Geographical coordinate grid along with UTM grid This option is available from Options Lat Lon grid menu item The following dialog allows user to specify grid see figurd20 49 Basic operation of MagPick Longitude and Latitude grid i x Grid annotation format Degrees and minutes Longitude spacing min fi Latitude spacing min f Grid color sd Labels Y North M South M West M East Digits after dot lo Ok Cancel Figure 20 Latitude and Longitude grid dialog 1 Draw Longitude and Latitude grid Check this box to plot lat lon grid The rest of the dialog 1s disabled if box is not checked 2 Grid annotation format Possible selections are e Decimal degrees e Degrees and minutes e Degrees minutes and seconds 3 Longitude and Latitude spacing Controls how often coordinate lines are drawn Note that units depend on selection of annotation format and can display degrees minutes or seconds 4 Grid color Press button to select color It is recommended to use brown because it contrasts with UTM coordinate grid lines and does not coincide with background color in DXF export 5 La
189. erval for instance 0 25 m is not suitable for Geoplot e Geoplot uses so called pixel registration for erids It means that first data point is in fact half of a sample interval from the grid border For instance for X range 0 to 10 m cell size 0 5 m first point for Geoplot has position 0 25 m last point 9 75 m total points is 10 0 5 20 For normal MagPick interpolation first point is O m last is 10 m total points is 21 To accommodate this requirement easily a special checkbox is provided Interpo late as for pixel registration record as grid registration This box must be checked to successfully export data for use by Geoplot 2 After grid is interpolated use can export it to XYZ file Use File Export XYZ and select Geoplot XYZ format Line and Sample decimation should be set to 1 If is known that if data exported as lines East To West then Geoplot select North arrow down If West to East then North arrow points up If MagPick starting point is SW and lines go North then Geoplot shows North direction in the right User may need to experement with this Select appropriate number of digits after dot Check Export dummy values as and enter value to mark dummies 2047 5 is default for Geoplot It is mandatory if your grid has gaps and it is safe to use it all the time After MagPick completes file export into Geoplot it shows data origin coordinates Write it down They are needed for Geoplot Magpick operat
190. es 4 Apply UTM on input It is the same option as offered in the Simple Load dialog It defines how and if UTM projection is to be used This option is mandatory for geographical latitude longitude data as MagPick only operates in a meters coordinate system The dialog has the following selections e No UTM to be used with local coordinate grids e Auto Short UTM UTM projection is selected automatically based on first data samples useful for small data sets 44 Basic operation of MagPick Choose data file s 2 xi Look in E 1211010 e ex E My Recent Documents Desktop 9 My Documents My ai File name E 21110_B0X 1_LINE 6 Survey INTERPOLAT Open Cy My Network Files of type MagLog interpolator INT y Cancel Places Open as read only Survey INTERPOLATOR INT LINTERPOLATOR INT POLATOR INT lt POLATOR INT INTERPOLATOR INT ey INTERPOLATOR INT _BOX 1_ _LINE _LINE _LINE _LINE _LINE 6 5 BOX 1 Figure 16 Multiple file selection dialog e Manual UTM Projection is fully defined by the user this option should be used for any large in depth analysis and interpretation projects 5 UTM parameters Press this button to manually adjust save or load UTM parameters 6 How to save list file The program can save a profile list file to be used for future loads The user can select Do not save Prompt user for a file
191. eshes Check Draw X grid and Draw Y grid and enter steps for the grids Alternatively you can check X autogrid and Y autogrid to let MagPick select the steps 7 Canvas size If 5 is on the picture always fits in the specified size in pixels If 5 is off size is chosen automatically to satisfy scale factors 8 Scales Scales for coordinates in physical units per display units pixels Adjust to find a value that works best If 5 is on the program sets these values automatically This may be the best way to get initial values It could be good initial values to start with Next important menu item is File Browse If this item has been chosen the modaless dialog box pops on the screen In this box you can choose any profile from the list you wish to see As soon as you click the mouse the picture is updated The active profile is highlighted on the map view as well You can navigate to the next or previous profile by using the using the buttons marked lt lt and gt gt If you want to see only part of the multi set data click on SubSet A dialog box appears for you to disable or enable plotting of the specific sensor It should be noted that Profile Browser dialog box has a different functionality in profile view and profile inversion view windows In profile view it is just a simple chooser You can see only one profile at once Accordingly only one line can be selected in the listbox Profile inversion view has more functionality y
192. et columns into the name For instance ID would just show target number as 1 2 etc and b ID would create way points with names b1 b2 b3 etc Annotation ID Z would create way points with ID and estimated depth Note that you always should use ID to make way points names unique 6 Garmin flag type Select icon to display waypoints in the GPS receiver This is mostly for Garmin users Not all receivers support all icons If icon is not supported by the receiver it uses its default Mapping software such as Garmin BaseCamp could honor this flag 189 Target position export Export targets as waypoints GPX x Ta rgets to export Name annotation E SID Use to include cell values such as x Use D to include target 1D Garmin flag type Default MV Load into GPS GPS protocol Select All Garmin Serial USB protocol Select None Port GPSBabel executable C Program Files GPSBabel gpsbabel exe a Note to load waypoints into GPS you need to install GPSBabol Please visit http Www gpsbabel org Ok Cancel Figure 134 Dialog to define waypoint parameters usb E 7 Load into GPS After GPX file is created GPSBabel software is called to upload waypoints into GPS device You need to have GPSBabel installed for this to happen and have GPS receiver connected to PC via USB or serial cable In latter case you may need to utilize serial to USB converter
193. eter data Mag field nT 8600 8650 8700 8750 8800 8850 8900 8950 9000 Y short Norting i H yo 8600 8650 8700 8750 8800 8850 8900 8950 9000 fh Figure 95 Profile view after inversion Synthetic field is shown with dotted line Good fit 145 Single magnetometer inversion Mag field nT 8600 8650 8750 8800 8850 8900 8950 9000 AMOO rr n beseeeeeeeeeeed EEE A HE epee a da t 43100 Line 7 i i i i 43050 ed A E S aen 43050 8600 8650 8700 8750 8800 8850 8900 8950 9000 Figure 96 Inversion did not converge properly Bad fit Mag field nT 8600 8650 8700 8750 8800 8850 8900 8950 3000 p gt 43020 42960 besesceeeeeees OS besseeeeceeees bescseeeceenee feseseeseseeee fe peeseeeee j Y short Norting 42960 8550 8600 8650 8700 8750 8800 8850 8900 8950 9000 ih Figure 97 Adjacent line covered by polygon nT 8800 8850 8900 43005 Y short Norting 8900 8950 9000 8600 8650 8700 8750 8800 8850 Figure 98 Adjacent line covered by polygon 146 Single magnetometer inversion 2 Dipole sheet iki tbl 4 P 768871 89 9435517 73 1 67 4 240e 000 3014 8 37 4 86 00 153 551 2 P 76887185 9435518 35 1 99 4 8938e 000 3139 6 441 86 02 153 551 Figure 99 Inversion work sheet Figure 100 Location of the dipole target 147 Single magnetometer inversion 18 1 Discussion about mass estimate for above case Even
194. etization All operations listed above could increase noise To cope with this the option of simultaneous upward continuation which acts as low pass filter is provided Use zero elevation to disable this option These transformations are available under Operations Reduction to the pole and Operations Pseudo gravity 7 gt Reduction to pole E Main field declination D degrees 30 00000 Main field inclination D degrees 70 00000 Declination of magnetization deg 30 00000 Inclination of magnetization deg 70 00000 D positive to East negative to West A positive to east negative to West positive down negative up Azimuth of local X axis deg 30 00000 Note Use IGRF model to find main magnetic field F Use reduction to pole New field declination D degrees _ New field inclination I degrees i Elevation up down 0 000 New declination of mag deg H 4 Regularization Parameter 0 0000e 00_ New inclination of mag deg Note Use zero elevation to avoid continuation File with transformed field F Add files to the history list Format NetCDF data misha projects magpick pseudo grd coc Figure 85 Reduction to the pole dialog in magpick Figure 85 shows the dialog box where transformation parameters are set pseudo gravity dialog 127 Estimation of magnetic sources box is similar
195. etween lines acquired North South and West East Ideally with sufficient amount of data acquired at different times even raw data should represent geological trend correctly But in this particular data set it represents a problem Data used in this example can be re gridded now and picture similar to the following can be produced see 60 92 Leveling tie lines Gridding with L2 leveled profile data 4260 4280 4300 4320 4340 4360 2840 2820 4240 4260 4280 4300 4320 4340 4360 Magnetic Field nT 50104 50106 50108 50111 50116 50122 50138 Figure 60 Grid on the leveled profile data Note that picture 60 is uses the same color scale as raw picture above but local anomaly is clearly seen In case of data analyzed in here L1 and L2 yield almost identical results 93 Quasi Analytic Signal 10 Quasi Analytic signal 10 1 Brief introduction to the Analytic Signal Analytic signal is widely used in magnetic data interpretation 8 9 It has the following advantages e It is always positive e It has a simplified signature only single maximum anomalies are normally present e It allows estimation of horizontal coordinates of the local object just by taking maximums of the anomalies e It simplifies depth computation with half width rules or Euler deconvolution The Analytic signal is defined as A G G G where G dT dx G dT dy G dT dz and Gy Gy G are orthogonal components of the gradien
196. etween observed and calculated field does not show errors due to wrong positioning depth readings etc They are typically much less than real errors Inclination Inclination in case of dipole inversion 0 for the cable This value may show dis tance from the beginning of the polyline this is temporately Declination J total Jx Jy Jz dipole related values 0 for the cable 160 Pipeline data treatment 21 Pipe line Total Field and Analytic Signal data treatment 21 1 Brief overview Pipelines are typically surveyed across the object and are observed in the Total Magnetic field as se quence of anomalies aligned along the pipe line route Despite simple nature of the object observed data normally show complex sequence of magnetic anomalies of different shapes and polarity This behavior is due to different magnetic properties of the pipe line material An experience shows mag netic properties vary as with pipeline segments as inside of each particular segment Figure 110 Pipe line Total Field data recorded during actual survey Data courtesy to Environmental Solution San Rafael CA If pipe line is interpreted as 2D object which implies that no variation is assumed along it each particular intersection delivers erroneous result In terms of estimated depth is means that some intersections shows deeper and some shallower values Based on the actual data it was shown that averaging across multiple intersections yields expecte
197. ews v NewFolder Grid functions Name Date modified T z Size De space folder Load Jtest gpx Jtestmin gpx Save Juntitled gpx P 5 64 Delete P 7 38 Find P 5 53 Undo Clear all Format positions File name Hide Folders Cancel First 8 63 24 83 Modify annotations Figure 133 This picture shows processing data flow to export target positions as GPX file with way points and optionally to load these way points into hand held GPS receiver Figure outlines the procedure User should export target positions into GPX format and optionally load into GPS receiver 1 Right click on the MagPick spreadsheet and select Export or select File Export menu File selection dialog is displayed 2 Select file type at the bottom of the file selection dialog as GPX waypoints gpx Under Linux just use file extension gpx Type new file name or select existing file to overwrite 3 Press Save The following dialog describing export procedure is displayed 4 Targets to export This list is used to select portions of the target list to export Use Select All and Select None buttons to simplify operation To export only particular limited number of target s press Select None and then manually select only targets you want to export 5 Name annotation This field controls how way points are named in the GPS receiver Use to include content of the spreadshe
198. file This would be good choice if you plan to use TIFF file in an office application such as MS Word or Corel Draw Additional tags can pose a problem for these programs and are not needed anyway 2 Export as simple UTM This option should be used if standard UTM projection has been used It saves minimum georeference information and assumes standard central meridians It also should be easier to use with GIS systems Below is the dump of listgeo exe program 177 Export and printing MagPick Points Export xj M Enable points export Position annotation format Digits after dot Report position as Lat Lon C Full UTM Short UTM Position annotation Balloon only y Google Earth folder name MagPick drawing file Ok Cancel Figure 126 Exporting points into Google Earth showing informat ion embedded in the TIFF file is simple UTM only useful if user is familiar with GeoTIFF specification Geotiff_Information Version 1 Key_Revision 0 2 Tagged_Information ModelTiepointTag 2 3 0 0 0 953184 312 8500765 5 0 ModelPixelScaleTag 1 3 0 0499889441 0 0499279872 0 End_Of_Tags Keyed_Information GTModelTypeGeoKey Short 1 ModelTypeProjected GTRasterTypeGeoKey Short 1 RasterPixellsArea ProjectedCSTypeGeokey Short 1 PCS_WGS84_UTM_zone_10N PCSCitationGeoKey Ascii 12 UTM zone 10 End_Of_Keys End_Of_Geotiff 3 Export as Transverse Mercator This option shou
199. files Interpolate grid and pick the interpola tion method you prefer Spline or Triangulate e Fill in the interpolation parameters and start interpolation After interpolation completed Magpick will save the map into a file and automatically load the newly calculated map into current map view or create new view if interpolation has been started from main menu Adjust the view parameters If you want first see the profile locations and possibly a stack profile plot go first to File New and pick Grid view The program will create an empty fake grid just to have a base to display profiles You can start interpolation from that window also 51 Grid operations e If you want to examine profile data and possibly modify it go to File New and pick Profile view Adjust the orientation along X or Y axis in the case of data collected with Geometrics G 858 magnetmeter you should choose Y You also can start the interpolation from the profile view under File Interpolate grid However a new grid won t be automatically loaded if you start interpolation here Keep in mind that there is no need to save the interpolated grid because it has been saved already However you might do it 1f you did some transformations or simply want to change the grid file format gt If don t know limits Enter grid steps Enter X Y limits of a new grid here check here and data Along X Y limits are used r Triangulation
200. files 200 300 m Tbackground ax Tpc Where x is the distance along the profile a is scaling coefficient and Tpc is a constant term The formulas above deliver only amplitudes of the anomalous field To be used with total field magne tometer they need to be re written in components and projected into direction of the Earth s magnetic field taking into account the direction of the survey line To simplify this operation let s assume that profile lines are perpendicular to the cable and in case if it is not there will be correction proportional to cosine of angle between survey line direction and cable direction The unit vector along Earth s magnetic field can be computed as ny cos D cos 1 ny sin D cos 1 nz sin Where D and are declination and inclination of the Earth s magnetic field the X axis is pointing East the Y axis pointing North and the Z axis pointing down X Y and Z could be defined using UTM projection for the area Consider the unit vector p py py pz along the data profile with p 0 if the profile is considered horizontal p is defined in the same system as 7i n ny n and can be computed using coordinates of the beginning and end points of the survey profile Formulas above are written in the profile coordinate system with x axis along the profile and z axis pointing down Projection of the Earth s magnetic field direction 7 into profile coordinate system is gt pn n Ax
201. formations You must save the profile data or the result will be lost after you exit MagPick To discard the transformation results go to Profiles Discard A grid view will be redrawn and the transformed part disappears 7 3 4 Using line shift file The above description assumes that all profiles are transformed the same way or user needs to process profiles one by one Latter is typical in case of various layback for different lines To simplify this operation ability to read layback values for each line individually from the file is added To activate this option check Read shifts from file box see picture 34 and select appropriate data file with the following format e First line header of the file can contain any information e Each of the following lines should have fields separated by at least one space 1 Line name or profile file name depending on File key selection in the dialog 74 Profile data transformations 2 Distance in meters to find initial direction of the profile 3 Method 0 for dragging or 1 for for shift along the line 4 Shifts dx dy for each data channel The convention is the same as for the rest of the dialog X is positive forward Y is positive starboard right 7 3 5 Dragging method details Here you can find a brief description of the method used to calculate the position of the fish being dragged behind the boat Text below refers to figure 35 Figure 35 Calculating magnetometer
202. fser and Y drawing Yscale X Ymagpick Yof fset For typical short to full UTM trans formation Xscale Yscale 1 Inverse UTM transformation This should be enabled only if the user wants to present a draw ing in Latitude and Longitude Attention should be paid to set correct UTM parameters If both linear and inverse UTM transformations are requested program first performs linear and then inverse UTM Note that false Northing and Easting are parts of UTM parameters see figure 81 Note that the text and arrow size should be set in the MagPick coordinate system The program recalculates sizes in the transformed system automatically To specify general title of the plot and axis titles press Titles Remove any text if you don t want titles All titles are plotted on the same layer as coordinate grid with slightly increased text hight Grid labels format controls how labels are printed The user can choose decimal degrees degrees and minutes or degrees minutes and seconds The latter two make sense if Inverse UTM is enabled in Grid labels dialog Regardless of which one is choosen the drawing coordinate system labels can be presented in UTM or latitude and longitude Figure shows a contour plot exported into a DXF file To obtain the contour labels slow contours should be used see 4 MagPick uses the text hight defined for the layer and fits labels into the space defined in the contour dialog box refiso Due to this operation
203. g PCSCitationGeokey Ascii 36 TRANSVERSE MERCATOR ELLIPS WGS 84 ProjectionGeoKey Short 1 User Defined ProjCoordTransGeoKey Short 1 CT_TransverseMercator ProjLinearUnitsGeoKey Short 1 Linear_Meter ProjNatOriginLongGeokey Double 1 123 ProjNatOriginLatGeoKey Double 1 0 ProjFalseEastingGeoKey Double 1 60000 ProjFalseNorthingGeoKey Double 1 4140000 ProjScaleAtNatOriginGeokey Double 1 0 9996 End_Of_Keys End_Of_Geotiff Local only This option only embeds local coordinate system information and not geographic information Coordinates are saved in full UTM form but no zone or central meridian is saved Typical dump of such a file would be Geotiff_Information Version 1 Key_Revision 0 2 Tagged_Information ModelTiepointTag 2 3 0 0 0 393184 312 4360765 5 0 ModelPixelScaleTag 1 3 0 0499889441 0 0499279872 0 End_Of_Tags Keyed_Information TModelTypeGeoKey Short 1 ModelTypeProjected TRasterTypeGeoKey Short 1 RasterPixellsArea End_Of_Keys End_Of_Geotiff Q Q Local with XFalse YFlase The same as above but UTM shifts are to be subtracted from the local coordinates The common usage is when picture is in local short UTM or State Plane coordinates and export is needed in full UTM or state plane coordinates Compression Possible choices are no compression and LZW First is recommended for some systems such as AUTOCAD which does not accept compressed TIFF f
204. gPick should be expressed in WGS84 MagPick does not provide datum to datum transfor mation UTM parameters This button is provided for convenience to enable the user to check UTM parameters without leaving the export dialog Export file name kmz GE export file name This file can be directly loaded into Google Earth software Use the button to navigate by file system and select the appropriate file name and location 171 Export and printing GoogleEarth export Items xi Elements to export MagPick Image Overlay Profile locations Estimated dipole locations Manual targets locations Points C data mosquito 11 10 09 air data battele iny pt Marks items selected for output Mark All Un Mark All Google Earth Folder Name MagPick data M Apply inverse UTM UTM parameters Export file name kmz C data mosquito 11 10 09 air data s3 s5 w inversion M Start Google Earth after file is saved Ok Cancel Figure 120 Calling Google Earth main export dialog Properties 8 Start Google Earth after file is saved Select this box to automatically launch GE after the file is saved or to load the file in GE if it is already running not available in Linux version Note that if the file is saved under the same name as a file already loaded in GE Google Earth asks if user wants to refresh the content of the file from the disk This is useful when u
205. gpick could be compiled 15 MagPick project files for any of these platforms but a working version described here is compiled with wx Xt libraries version 166d Follow the instructions to install wxWin library During configuration make sure that the usage of Xlib is enabled You will need wxgrid library which is part of wxWin A nicer view of worksheet can be obtained obtain with a patch from ftp ftp aiai ed ac uk pub packages wxwin contrib wxgridd wxgrid_d tgz It is worth checking your installation using test demo programs that comes together with the library When you have all these libraries and gcc C compiler installed you can start the compilation ofMagPick 3 2 Compilation Make a subdirectory and unpack file magpick tgz with gzip and tar programs Edit the file make file xt to match you site configuration You will need to change the next variables in the makefile xt WXDIR points the root of your wxWin installation e INC points include files folder s If your netcdf library is not in the system place set its include path too THISDIR is current location where sources are e LDFLAGS linker flags where all libraries can be found This should be the path to wxWin and netcdf libraries e LDLIBS Selection of the libraries If wxWin on your system requires additional libraries you should alter this list After altering the makefile you can type make f makefile xt and likely end up with the file
206. he Cyrillic stuff The fonts are in KOI 8 and taken from ftp ftp kapella gpi ru pub cyrillic psfonts ArialCyrMT arial8 pfa ArialCyrMT Bold arialbd8 pfa ArialCyrMT BoldItalic arialbi8 pfa ArialCyrMT Italic ariali8 pfa A AS ERKurierKOI8RBold cokoi8b pfa ERKurierKOI8RBoldItalic cokoi8bi pfa ERKurierKOI8Ritalic cokoi8i pfa ERKurierKOI8RRegular cokoi8n pfa CourierCyrPS cour8 pfa CourierCyrPS Bold courbd8 pfa CourierCyrPS Bold0blique courbi8 pfa CourierCyrPS Oblique couri8 pfa TimesNRCyrMT times8 pfa TimesNRCyrMT Bold timesbd8 pfa timesbi8 pfa TimesNRCyrMT BoldItalic TimesNRCyrMT Italic timesi8 pfa Sometimes talic can be referred as Oblique or Inclined It could be a good idea to repeat font names with the same actual font files but with different aliases CourierCyrPS Oblique couri8 pfa CourierCyrPS Inclined couri8 p b CourierCyrPS Italic couri8 pfb Now finally changes in the magpick ini take effect Note that font names there should match names in the Fontmap GS 23 Export from worksheets MagPick allows export from its worksheets manual targets and dipoles into variety of formats They are covered in this section 23 1 Export target positions into GPS exchange format GPX and load into GPS receiver as way points Besides exporting targets into spreadsheet applications as
207. he active profile and based on user marks 4 or A which can be up or down arrows To perform cutting the user must place marks on the appropriate place and call Edit Cut The operations are applied to all data channels if there are more than one Terms before and after used below to denote distances from the beginning of the profile It is strongly recommended to use this feature when the profile is plotted as a function of distance plot mode Along profile 63 Profile data transformations For example you might be confused if your profile is going north south and plotted as function of Y Then when you cut the beginning of the profile the northern part is getting cut not southern part with small Y In case of error call Edit Reload This reloads your profile data from hard disk and restores the initial profile configuration After profile being cut you have to redraw the map view 1f you have one to see any new profile location Here are four possible profile cut operations e Cut from the start of the line to the UP marker If UP marker is set the program removes all data from the beginning of the line untill the UP mark and redraws a profile view If plot mode is Along profile it also shifts the data in the view because now the profile has a new starting point e Cut part after UP marker to the end of the line If the UP marker is set then all data after it gets removed and the profile view is updated Cut outside UP and DO
208. his means that you are seeing all these lines simultaneously in the profile window not one by one as we did in the Profile view and this new window has the word Inversion in its title Adjust the profile view parameters Go to Parameters Settings and set Type Along Y data were taken along Y You are looking at a classic dipole field Let s work with this now Go to File Browser you can see that all lines are selected Press the button Deselect All Now view window is empty Select some lines from the list You see that you are able to select more than one line When you click on an already selected line it gets unselected Some explanation should be done at this point This new profile window we are work ing with now is the counterpart of the map window from what we called New Profile inversion Only one such window can be opened per one map view window This profile inversion window has some extended properties It can display more than one profile it shows the data as function of direction and it can use the profile data for inversion Press Deselect All now Go to the magnetic map window choose Edit Pick profile pick several profiles which cross the magnetic anomaly Check that you can see them on the profile inversion view On the magnetic map go to Edit Direction Point the mouse somewhere in the middle of map window Click left button move mouse approximately 45 north east and click left button again The arrow sign is now o
209. ic field e Next line with F and name of the file This file can be used for further presentation or processing It is overwritten for each inversion In order to save data you have to change its name before the next inversion starts It is possible that there were many inversions done in the particular window Until the window is closed the program keeps track of all of them open Inversion Remove results and you will see the beginning of the line for each inversion that belongs to the window Thus unnecessary results might be safely removed and a work sheet window automatically altered If a window has been closed the only way to remove the results is to do it directly in the work sheet window 16 3 Magpick worksheet results of inversions For convenient storage and presentation of the inversion results MagPick maintains special object work sheet electronic table This object is global Only one copy exists during a session and all the inversion results are appended in it The work sheet can be saved or loaded from file In case you are about to quit MagPick without saving of modified work sheet you are warned and allowed to save it The work sheet file has a column structure Here is the meaning of the columns 1 Type of results letter G for grid results or letter P for profile results X coordinate of the dipole Y coordinate of the dipole Z coordinate of the dipole attempt to estimate mass root
210. ick After this lesson you should be able to load grid data into the program adjust size of the view pick appropriate color scheme and the coordinate mesh You will learn how to zoom parts of your map to see details with Magpick Files for that lesson we take file helens2 grd which comes with the standard SURFER distribution if you are using SURFER 7 convert this file in ASCII grid or SURFER 6 binary format using SURFER 1 Check initial state Start magpick from Windows explorer shortcut or command prompt this does not make any difference Go to Options Size Make sure that X size cell and Y size cell are set to 1 These are hight and width in pixels of one cell of your grid data on the screen Let Zoom be something like 2 or 4 and check autoscale on zoom Press Ok Go to Options Settings Common parameters dialog pops on the screen Uncheck here all check boxes except Autoscale and Colored map Note that when you check Colored map another dialog appears In this dialog select Drawing mode Simple color map and press Ok Press button Change palette choose Uniform press Ok The uniform palette preview appears make sure that the palette number is 34 and the Equalize colors dialog box is checked Press Ok to close this box and once more to close Common parameters You are now ready to load the data 2 Pick and load the file Inspect result Go to File Open and pick file helens2 grd After reading and color equaliza
211. id presentation because user has to supply true grid origin 60 Profile data transformations It should be pointed out here that Geoplot is very picky about importing external data Any mismatch with the above procedure may result in refusal of data import It is not actually very clear how Geoplot treats the import of external data in particular North arrow assignment and you may need to consult the Geoplot manual about this 7 Profile data transformations This section describes the MagPick features which allow to modify loaded profile data It includes the following 1 Saving profile data Certainly profiles must be saved if any transformation has been used Note that new profile list or Simple load menu call might be necessary in order to load saved data into program next time You can save only the only profile parts inside the polygon This allows to cut unnecessary sections of the data to be removed Profile cutting These operations can be used to remove part of the active profile It is based on user marks Profile data smoothing A simple cubic spline can be used to smooth data magnetic field along the profile Profile position shifts Any or all profiles can be shifted with constant offsets along X and Y axis Profile position smoothing Any or all profile positions can be smoothed with some type of cubic spline Profile position recalculations based on the profile direction This
212. iform choose number 33 and check Equalize colors We are ready now to load our file Please note that your are free to adjust settings above anytime after the file is loaded We did it now just to insure proper initial appearance of the picture Now go to File Open and pick g 858m grd You have two windows on the screen now one with profile data and another a magnetic map with blue vertical lines which shows profiles position Simple profile map interaction Go now to the profile view and change horizontal axis Parameters Settings then Type Along Y You can see a field that was taken along Y Note that the right profile line on the map view is highlighted by red This is the same line we see in the profile view window Again in the profile view go to File Browse in Profile browser dialog press button marked gt gt You can see that a red line on the map view is moving to the left and field in the profile view window changes You know exactly which profile you are looking at Now in the map view go to Edit Pick profile cursor changes its shape Point cursor on some line and click left button The line you are pointing at becomes red and picture in the profile view window changes as well This is the way you can directly inspect profile information by picking the line you want to see from your map You do not need Profile browser dialog close it for now 222 Tutorial The next step shows how you can tie points on the profile with p
213. ile graph Program finds anomaly type and reports its parameters as 1t is shown in the spreadsheet 103 Simple magnetic anomaly positioning The parameters xp z J are estimated as part of the approximation The variable xo is target position in the profile coordinates which is converted into X Y and reported as target position z is the depth of the target from line of observations it can be reduced to the sea floor or water level and reported as depth The altitude of the sensor is used to report off line offset The ratio of monopole and dipole terms is used to identify target as dipole or monopole see figure 88 In MagPick result of the approximation is shown with dotted line and there should be a good fit between this line and the observed data for target to be accepted Simple profile pick type selection xj Type Approximation with signal classification Channel 2 How to report depth MIES Depth from water surface or sea floor is only reported if depth and or altimeter readings are available Approximation dipole monopole curves decision ratio fo 1 Number of dipole targets for approximation hr Y Use amplitude constrain gt ls M Use depth constrain from 5 to l5 Y Use discrepancy constrain gt leo J Post no warning if not accepted Ok Cancel Figure 69 Simple profile pick dialog approximation parameters are shown Simple pick dialog has the following parameters 1
214. ile selection options 1 Geoplot XYZ format This is specialized format useful if you are using commercial package called Geoplot It is covered in details below in this section 2 Generic DAT format It has to be used for all other applications The output format consist of four colums X Y DATA LINE where line is column or row number of the original grid The following dialog 26 is called when menu is selected Here the following export options can be set e Starting point Select where first exported profile starts It can be any corner of the grid such as NW SW NE SE top left bottom left top right bottom right 57 Grid operations Export grid data as XYZ x Starting point Profile direction NW CNE Vertical CSW CSE F ZigZag Line decimation T 14 50 Sample decimation 7 1 gt 50 Coordinate decimals 9 O 4f ul us Data decimals 3 O _ gt 12 gosoecesessesesescesesoseeoesesocosoceoeosooeceseoossssesosossecessessoseseosossosseseessseeeg I Export as Lat Lon inverse UTM UTM setup A AAA AAA Export dummy values as fi e 007 oK Cancel Figure 26 XYZ export dialog Profile direction This option controls how new exported lines are created They can be crated by column vertical or by row horizontal ZigZag If this option is not selected all lines have the same direction If option is selected lines are going in opposite directions For instance if
215. iles Length units Encodes units into the GeoTIFF file This option is only available for local co ordinate systems local or local with Xfalse Yfalse Allows handling State Plane coordinates units are feet or U S survey feet can be encoded Create TFW world file This file is great simplification of georeferencing information en coded into the GeoTIFF file itself It is used by some GIS systems and AUTOCAD If box is checked file is created automatically with extension tfw and the same root file as Geo TIFF file itself Note that file also can be created by free software available from www remotesensing org geotiff geotiff html 180 Export and printing 22 4 1 Saving profile windows into TIFF It is also possible to save profile windows into plain TIFF In this case program does not save any ref erence information just the compressed image To use this function activate profile view and select File Save TIFF menu You are prompted for the file name Type new name default extension is tif or select existing one 22 5 Preparing printouts via Postscript MagPick uses Postscript PS to prepare document of presentation quality This option is currently only available for map views grids under File Picture export Postscript menu To be able to view print and convert Postscript files the user should use Ghostscript software It s also very beneficial if user downloads GS View which is a fully functional share
216. iles Google Earth line width h M Show line start stop markers Output every ho data samples Ok Cancel Figure 122 Exporting profile locations to Google Earth 1 Enable Profiles Enables or disables this element for export No profile locations would appear in the GE map if this feature is disabled 2 Google Earth line width Line width used by GE to draw profiles Minimum possible is 1 Note that when the user clicks on the line in GE a balloon with line information is displayed 3 Line color This button calls a simple dialog to select line color and its transparency level 4 Show line start stop markers If this option in enabled the start of the line is marked with a green ball and end of the line is marked with the red ball If the user clicks on either of them the line information as well as words start or stop is displayed 5 Output every data samples To reduce GE overhead it is possible to reduce number of exported points For instance if 10 is selected it means MagPick exports only 1 11 21 etc data points This option makes smaller kmz file and allows faster handling by GE Note that last reading of the line is always exported Stack profile plot if enabled is fully exported 22 2 3 Estimated dipole locations MagPick provides target location through a dipole pattern fitting inversion If inversion calculations were carried out and a dipole worksheet created it is possible to expo
217. imate errors introduced by these sources for each particular configuration Figure 36 shows two different offset calculation methods They are based on real GPS data which represents a ship turn after it passed the Golden Gate Bridge in San Francisco Bay the data was converted into short UTM MagPick was used to calculate the offset with a hypothetical cable length 250 m and an offset to the right 20 m offset was taken after dragging has been used The left pane represents the result of shift along a GPS track and the right represents a result of the dragging method 7 4 Splitting profile lines in place Starting with 11 12 2012 MagPick provides function to split profiles directly in memory without necessity to save data onto disk and then reload with split by distance enabled This eliminates additional files shortens the procedure and allows you to keep original line names if desired In this section step by step instructions are presented Assuming profile data with turns are loaded as it shown in picturd37 First draw a polygon surrounding the data you wish to retain Right click on the canvas and select Add Add polygon as shown on picture 38 Make sure that polygon is selected for clipping Newer MagPick versions draw such polygons with horizontal hatch Double click on polygon border and and make sure Use polygon to clip data check box is checked as shown on picture 39 76 Profile data transformations
218. in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EX PRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MER CHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFT WARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE 1 3 Info Zip Copyright Notice Copyright c 1990 2007 Info ZIP All rights reserved For the purposes of this copyright and license Info ZIP is defined as the following set of individuals Mark Adler John Bush Karl Davis Harald Denker Jean Michel Dubois Jean loup Gailly Hunter Goatley Ed Gordon Ian Gorman Chris Herborth Dirk Haase Greg Hartwig Robert Heath Jonathan Hudson Paul Kienitz David Kirschbaum Johnny Lee Onno van der Linden Igor Man drichenko Steve P Miller Sergio Monesi Keith Owens George Petrov Greg Roelofs Kai Uwe Rommel Steve Salisbury Dave S
219. indow will be choosen in accordance with local minimum and maximum This may allow you see fine details in the view This kind of color zooming is very useful The first view you see may not be what you want To adjust color scale mesh lines contours ap pearance and other items you should go to Options Settings and work in Common parameters dialog box You can see it on figure 3 Here is full explanation of all the controls 1 Field direction Some constant angle value which is used for simple picking see below 21 Basic operation of MagPick 2 Minimum and maximum values of the field Data is mapped in this range 1 Constant angle to be added to pick not important 13 Plot coordinate meshes for X and Y F F Common parameters r 0 0000 Data min 223 95 JT Show x grid X 50 Data max 353 52 11 Allow you to select lT Show y grid LY 50 F Autoscale color for coordinate Y wrap ceb sale mesh b Grid color gt 3 If this is checked minimun and maximum are taken from the data 12 Coordinate mesh steps Field direction for X and Y 4 If this is checked color is wrapping data repeats itself when out of range 3 Snap to grid F Show profiles 1 Color map 10 If checked picks are 5 Allows you to specify eis to the grid 3 Contours FT Show crosses
220. ine magpick_xt or under MS windows with in this case you also can start it from Windows Explorer or create shortcut to desctop 20 Basic operation of MagPick magpick exe MagPick first tries to read the file magpick ini from the MS Windows directory windows 95 98 or from user profile directory Windows NT Under Uxnix like systems MagPick reads the file magpick from user home directory These files hold settings of the program which can be altered by different dialogs This file is written right after magpick exits If file is not found all defaults are assumed If start is successful you will see a small window with a menu under Uxnix X does not support MDI interface or an empty multi document window MDI window under MS Windows This is the root window of MagPick which remains unchanged during the session Uxnix Besides this root window you can have as many additional windows as you wish These windows are called views The current version of MagPick allows you to have three types of views 1 Map view This is a 2 D coloured or black and white map of the grid with additional informa tion if desired This view is independent from all other windows 2 Profile browser view If a set of profiles is loaded into the program you can browse each one of them as 2 D linear graph This view might be linked or not with map views s 3 Profile inversion view You can see all or part of the profiles which cross the parent m
221. ined di rection North and Grid to draw direction to the geographic north and grid line latter always vertical because MagPick uses UTM projection or North Grid and Magnetic the same as above but with magnetic North direction drawn as well 2 Simple Arrow direction It is only applicable if Simple is selected as arrow type It can be Geographic North UTM Northing Magnetic North in this case arrow is annotated with MN letters or user defined azimuth Desired azimuth should be entered below The rest of the dialog duplicates simple annotation properties such as background and frame color annotation font size color and pen width 204 Map annotations 25 1 4 Map scale D This annotation can be used to visually show typical distances in metric or English units or both It is available under Add map scale context menu User can define its appearance using properties dialog shown on figure Map scale properties x Map scale mode AMEN Scale units meters v Scale length units fico Tics E Hight pxls ls IV Fill with solid color Fill color T Draw border Border color E Pen width lo Scale color A Font size mom nia m gt 100 Ok Cancel Figure 152 Map scale properties dialog 1 Map scale mode This can Automatic or Fixed length values In the first mode program selects scale length using screen size In the second mode length is set to the Scale length
222. ines with their own X Y positions This way magnetic anomaly is recorded simultaneously with multiple sensors and can be easily inverted It has to be pointed out that because sensors are synchronized influence of the magnetic field time variation is much less than in case of single magnetometer where base station correction is really required The simplest rudimentary version of the magnetometer array is Transverse Gradiometer TVG which consist of two magnetometer sensors see figure 102 water surface water surface water surface water surface Figure 102 2D inversion vs sensor array inversion There is uncertainty in case of single magne tometer magnetometer array allows true XYZ positioning It has to be noted that it typically positions objects sideways from survey line Typical magnetometer array inversion includes the following steps 1 Load sensor array data such as TVG In latter case profiles will appear on the map as double lines one line per sensor 2 Open profile view window and adjust X axis as it is convenient Option Along profile would be appropriate in most cases 3 Go line by line and limit anomalies of interest by markers note that as much data as possible should be included not only peaks There should be about 20 anomaly free ends on each side of the anomaly 1f possible Use zoom in if needed 4 In case of multiple dipoles use MagPick pick feature for initial position of the targets For sing
223. ing Possible values are 1 2 4 Higher value pro duces smoother font rendering e dGraphicsAlphaBits 4 controls line art anti aliasing Possible values are 1 2 4 Higher value produces smoother lines 22 6 5 Clipping PS file In certain cases you may have half of your paper blank due to scale of the map You might want to cut that white area before converting into PDF or TIFF file This can be relatively easy accomplished if left bottom corner of the plot is appropriately located and all that is needed is to cut white area in upper right corner Follow this procedure e User zoom buttons to view the whole picture e Move mouse cursor to the point you would like to become upper right corner e Write down point position from GS View status bar at the bottom of the window Do not forget units pt mm or inch 186 Export and printing e Go to Media User defined menu e First enter new wight with its units like 7 7 inch or pt or mm In the next dialog enter width with its units like 8 8 inch or pt or mm GSView cuts upper right corner Now you can export into PDF or TIFF and files will not include excess white space 22 7 Using Cyrillic Russian text in MagPick By default MagPick operates with Latin character set However it is possible to make it work with other character sets Below is a description how it can be done for Russian letters 22 7 1 Screen fonts Modify file magpick ini It is typically lo
224. initial depth which is more thanthe conceivable depth of the magnetic source In general inversion based on profile data is less stable than inversion based on a map It depends on profile distribution in space For example if you are trying to find the position of a source which is aside from your profiles it might be unstable The case when the source is between your profiles is much better 4 Worksheet operation Results of the inversion are displayed in the worksheet window Only one such a window for example for dipoles exist and once you have opened this window you can not close it it hides if you close it MagPick worksheet window is not the same type as a worksheet in Surfer or Excel It allows only some basic operations which are listed here All functions are available by window menu and by pop up window right mouse button e Left mouse button highlights current row e Open Load Load file into the worksheet The file should be a space or tab separated set of columns You may need to redraw to see loaded data e Save Saves worksheet content into simple ASCII file When you have a large project it is recommended that you save your data from time to time e Delete Removes current row from worksheet and from the map Re numerates dipoles e Undo Operation opposite to delete Restores eventually removed row Export Export worksheet content into form readable by other software Presently there are two choices Atlas Boundary
225. into this data file Note that turn removal does not affect profile data loaded into Magpick memory To access modified data set data should be re loaded from the file MagPick can do this automatically 7 Load data upon completion If this box is checked new profile data is loaded back into Magpick automatically Previously loaded profiles with turns are discarded Magpick also creates profile list file with extension 1st and the same name as data file After turn removal procedure is complete but before new profile set is loaded program shows information dialog figure 3 1 information i Total turns Found 12 Data removed on turns 5 70 Figure 31 Number of removed turns and percent of discarded data In this example the information dialog states that program has found 12 turns and 5 7 of all data belongs to those turns If number of detected turns or data percent is unusually high it indicates that turn removal probably did not work properly Inspect the result you may want to load original data set adjust turn removal parameters and repeat the operation After user presses OK button program loads new data set if it was requested in dialog B1 66 Profile data transformations 7 2 3 Data smoothing MagPick allows simple data transformations such as smoothing using a cubic spline Data is consid ered to be a function of a fiducial number n first point of the line has number 0 next 1 etc Note this usage is
226. ion is complete here The resulting file can be imported into Geoplot Geoplot part 1 5 Start Geoplot go to File Import data Select default template Odefault gip and data type as Grid Press Next In Import Data dialog select Survey type as User Defined instrument as Use defined Click Next Fill in Grid input Template Note that parameters here must match those in MagPick For instance if you interpolated in MagPick X 5 10 meters Y 5 20 m you should select Grid length x as 5m 10 5 5 and Grid width y as 15 m 20 5 15 Select the same sample and traverse intervals as in MagPick for most cases they are the same Set direction of the lines this matches direction in the MagPick export dialog Assign new name for a grid It appeared that Traverse mode in Geoplot does not affect import results Press Next In the next dialog use XYZ CommaSV format and select your XYZ file Select Reference Corner as Bottom Left and type in coordinates reported by MagPick after export Those are Reference X Coordinate and Reference Y Coordinate X Increment and Y Increment are filled in by Geoplot Make sure Dummy value matches value used n MagPick Press Ok to actually import the data If Geoplot reports that import is successful close all dialogs You are ready to load new Geoplot grid Go to File Open Grid Composite and load your newly created grid Tt is not quite clear It seems it uses some mixed form of gr
227. ion is complete user can select Edit Accept menu from within profile window Here is the selection dialog Similar to the profile line by line smoothing it is possible to select what value should be accepted for further processing If user is not satisfied with the filtering results they can be discarded by selecting Edit Dis card menu 9 Leveling magnetic profile data with tie lines 9 1 Notes of the method implementation It is well known that the Earth s magnetic field changes over the time Typical magnetic field variation during the day can reach 30nT or more affecting survey data As a result lines collected at different times have different field levels When attempt to interpolate grid map is made the resulting map could be a poor quality one because of this 87 Leveling tie lines 49950 49900 rn den 49900 Il Original field f Polynomial model Figure 53 Preview of the polynomial trend in the profile window The most universal way way to reduce this effect is to use a base station a dedicated magnetome ter stationary located at the magnetically quiet place Data recorded with this unit are subtracted from the field observations on moving platform on the time basis This solution is not always feasible a separate magnetic sensor should be readily available convenient and quiet place located a separate operator could needed to keep vehicles and people away from the sensors etc It especially hard
228. ion representation oe Da 7 5 a aa Titles Grid labels format in the DXF file Recommended Select grid labe 2 for drawings in UTM and 9 format Regardless of file name Browse for drawings in Lat Lon drawing system labels ARA EN can be in short or full Ok Cancel Press this button to select name of output file UTM of Lat Lon Figure 114 DXF export dialog Entities are not included in DXF file if not checked Enables includes layer in the drawing Line style for the layer Example 5 2 means 5 units draw and 2 units pen up No spaces in this string allowed Set layer line width currently not working Use colors defined in magpick instead of color by layer Layer s name Assigned by magpick but can be changed by the user XF layer Profile lines hb Enable layer Name PROFILES Line style al Text arrow size 1 Line width ol Color 4 Use magpick colors Ok Cancel Color for the layer Figure 115 DXF layer properties e Line style MagPick uses the following convention to code line style digit1 digit2 where digit is length of the line dash If digit gt 0 then line is drawn pen down if digit lt 0 the pen moves without drawing the line Example 5 2 produces line 2 meter gaps each 5 meters Spaces are not allowed in the line style definition e Text arrow size In some cases these
229. irection This controls where positive parts of the anomalies will gravitate if positive anomaly direction defined by one of the three methods described below is between 90 90 from this direction it is mapped If it is not that it gets flipped before plotting If Use fixed direction is not selected then MagPick estimates direction of data plotting based on perpendicular to the track If the positive anomaly is between 90 90 degrees range from Preferred direction it is plotted if not it gets flipped before plotting Please note that this method requires a smooth enough track line which is not always available especially for data acquired with GPS Fixed direction is taken clockwise from north Type This allows to select method for finding plot direction for the anomalies Choices are Normal to path Fixed direction and End points If Normal to path is selected then field is plotted perpendicular to the path at every point Preferred direction value is used to distinguish between positive and negative anomalies This method requires a smooth enough track line which is not always available especially for data acquired with GPS Small irregularities in the positions result in big spikes on stack plot If Fixed direction is selected then positive anomalies are simply plotted in that direction and negative ones are plotted in opposite direction Angle is taken clockwise from North End points works similar but direction is f
230. is the recepie from Eric Fischer on how to use GeoTIFF with AutoCAD 213 Coordinate transformation using Corpscon software Geotiff parameters l x Projection type TIFF compression No projection plain TIFF Export as simple UTM Export as Transverse Mercator Local system only Local with Xfalse Yfalse mo compressionging Length units local only Jus Survey Foot gt JV Create TFE world file Ok Cancel Figure 161 GeoTIFF export dialog for State Plane and AutoCAD If you have an older version of AutoCAD which makes georeferencing difficult there is an ap plication which will make it work Here is how 1 Download GeoRefImg vlx It is available for download from the internet at no charge 2 In autocad type appload and hit enter Select GeoRefImg vlx and load Close the menu 3 Insert raster image geotiff at any scale or location 4 Type georefimg and press enter It will prompt you to select the image Select the geotiff and press enter It will automatically read the tfw file and apply it to the image It should then snap into place and be correct 5 If the above does not work make sure the tiff file and the tfw file have the same file name and are in the same folder or location 214 Tutorial 27 Tutorial 27 1 View grid files with MagPick Goal Show how grid information presented in SURFER ASCII format can be loaded and viewed with MagP
231. is used Fiducial or Time and brief results maximum intersection difference before and after the leveling 26 nT and 1 9 nT in the case above and average difference before and after leveling 20 nT and 0 32 nT here User presses OK button and leveling is complete Depending on how results are stored additional steps might be needed If results are stored as Preview as smoothed user needs to open profile view window and accept the result similar to back 91 Leveling tie lines Leveling results x Using TIME as independent variable Max difference before leveling 26 after 1 9 Discrepancy before leveling 20 after 0 32 1 Least Squares estimation by SYD Figure 58 Leveling complete status message ground operation In the leveling case All profiles Smoothed field values should be selected to replace original values with leveled one Figure 59 shows the preview user can see in the All profiles window Leving preview in the All profiles window ny 4240 4260 4280 4300 4320 4340 4360 e t o Yi i i h i tj Siaa EY eh 4240 4260 4280 4300 4320 4340 4360 Original data X meters Leveled data Figure 59 Profile data preview after leveling is complete Here horizontal axis goes West to East therefore tie lines South North are shown as short dashes It can be seen that leveling has introduced spatial trend which is not present in the original data This is because raw data has considerable DC offsets b
232. it is appeared to be very large mass 3 tons it is not such unrealistic as one might thing Note that magnetometer elevation was about 7 m and side distance from the profile line is 7 m as well which yeilds total distance of 10m with recorded anomaly 150 nT If we use nomogram from page 43 of Application manual for portable magnetometers by Sheldon Briner shipped with each Geometrics magnetometer on CD we can see 100 GAMMAS gt boa g FEET 2 4 6 Ib 2 40 60 80 100 150 200 CENTIMETERS 100 200 400 600 800 1000 20000 3600 4000 DISTANCE FROM MAGNETOMETER gt Figure 101 Approximate chart to estimate object mass Geometrics Inc According to this nomogram 1 ton of iron creates a bit over SOnT at distance of 1000 cm 10 m Anomaly recorded here is 150 nT which leads to the conclusion that mass should be around 3 tons As always one should take into account that magnetic properties are vary in order of magnitude which would affect mass estimation 148 Array inversion 19 Using magnetometer array for dipole data inversion In the previous section single magnetometer data inversion has been presented It was noted that user must select multiple survey lines for inversion otherwise only range of the object could be estimated see also 2D inversion 17 5 It is beneficial to measure magnetic field with transverse magnetometer array where multiple sensors cover multiple survey l
233. ith no spaces allowed within name value pair 116 Geographic projection transformations UTM and PROJ MERIT a 6378137 0 rf 298 257 MERIT1983 SGS85 a 6378 136 0 rf 298 257 SovietGeodeticSystem85 GRS80 a 6378137 0 rf 298 257222101 GRS1980 1UGG 1980 IAU76 a 6378140 0 rf 298 257 IAU1976 airy a 6377563 396 b 6356256 910 Airy 1830 APL4 9 a 6378137 0 rf 298 25 Appl Physics 1965 NWL9D a 6378145 0 rf 298 25 NavalWeaponsLab 1965 mod_airy a 6377340 189 b 6356034 446 ModifiedAiry andrae a 6377104 43 rf 300 0 Andrae1876 Den Iclnd aust_SA a 6378160 0 rf 298 25 AustralianNatl amp S Amer 1969 GRS67 a 6378160 0 rf 298 2471674270 GRS67 IUGG1967 bessel a 6377397 155 rf 299 1528128 Bessel1841 bess_nam a 6377483 865 rf 299 1528128 Bessel1841 Namibia clrk66 a 6378206 4 b 6356583 8 Clarke 1866 clrk80 a 6378249 145 rf 293 4663 Clarke1880mod CPM a 6375738 7 rf 334 29 Comm desPoidsetMesures 1799 delmbr a 6376428 rf 311 5 Delambre1810 Belgium engelis a 6378 136 05 rf 298 2566 Engelis1985 evrst30 a 6377276 345 rf 300 8017 Everest1830 evrst48 a 6377304 063 rf 300 8017 Everest1948 evrstS6 a 6377301 243 rf 300 8017 Everest 1956 evrst69 a 6377295 664 rf 300 8017 Everest 1969 evrstSS a 6377298 556 rf 300 8017 Everest Sabah amp Sarawak fschr60 a 6378 166 rf 298 3 Fischer MercuryDatum 1960 fschr60m a 63
234. its m no_defs It can be seen that projection type is Lambert Conic Conformal proj lce with two latitudes at 30 7N and 29 5N and central latitude 28 5N and central meridian at 9020 W Ellipsoid is GRS80 and projection units are meters There are datum transformation parameters in this example 12 6 Defining projections with PROJ command line MagPick follows cs2cq command line syntax in defining projection using from and 1o state ments Here is list of links of useful resources as of 02 16 2011 1 PROJ home page http trac osgeo org proj cs2cs stands for coordinate system to coordinate system 115 Geographic projection transformations UTM and PROJ 2 Manual page for cs2cs program http trac osgeo org proj wiki man_cs2cs 3 PROJ manual ftp ftp remotesensing org proj OF90 284 pdf 4 General notes on projection parameters 5 List of most common projections with their parameters geotiff proj_list 6 EPSG registry web site also available for download In this manual some basic information is given along with some practical examples 12 6 1 Typical usage 1 While loading profile data using Simple Load or Load by Template select Auto short UTM Program will try to assign appropriate projection parameters based on projection used last time If you used PROJ and wanted to switch to built in UTM you need to clear proj check box and call Auto short UTM again The same is applicable if rotation was u
235. its shape to reflect this selection pressing left mouse key places the object on the map After object is placed it can be dragged by the mouse to any location resized or modified All objects currently on the map can be modified saved or loaded into the file by selecting Edit All menu item The modaless dialog see figure 146 is controls annotations Here the following functions can be used 1 Edit Access and modify properties of the object currently selected in the list 2 Remove Remove currently selected object from the map There is no undo for this operation unless objects were previously saved into the file 3 Remove All This removes all objects from the picture There is no undo for this operation unless objects were previously saved into the file 199 Map annotations Annotations Ix North Arrow 1 Map Scale 2 Edit North Arrow 2 Remove Rectangular 7 North Arrow 3 Stack Scale 1 Remove all Centre Rectangular 10 Save Rectangular 11 Rectangular 12 Load Rectangular 13 y tetik I Stick loaded to borders Figure 146 Annotations control dialog 4 Centre Brings currently selected object to the center of the map This helps if object got lost due to different coordinate systems used in for different maps After object is centered user can bring it manually to appropriate location 5 Save Save all objects into the text file Objects are saved with their
236. ixed position enter The same as above if data is not in UTM projection but in some local coordinate system The typical example is land G 858 survey with position ing marks used and no recorded GPS In this case user is required to enter approximate geographic coordinates of the area One digit after dot would suffice in most cases The coordinates are decimal degrees Individual points slow For large areas IGRF values can be computed individually for each data point This method is mandatory when long profiles such as trans Atlantic data are loaded This option can be very time consuming 3 Longitude dec deg Latitude dec deg Geographic coordinates to be used when only one point is computed see above 69 Profile data transformations IGRF profile computation Where to apply an profiles Pasitions Middle point of all data Longitude dec deg Latitude dec deg 53 Altitude Fixed value Altitude fixed value lo Altitude units meters Data channels hr 2 M Use fixed year decimal 2000 IV Use Inverse UTM UTM parameters Value to compute Preview color GREEN OK Cancel Figure 33 IGRF profile computation dialog Altitude Altitude of the data can be considered fixed and entered below For most marine and land surveys unless survey is conducted in the highland area Altitude can be fixed as zero and entered in the box below If the
237. ize of the median window is defined in number of samples here 6 Channels Channels to export 7 Units Text annotation to be added to each exported point For instance depth marks along the profile can be presented in meters Right part of the dialog controls graphics MagPick or MagLog export appearance It has the following controls 1 Font size Size of the font to be used to annotate point information 2 Color For MagPick formats only controls color of the lines or points 3 Mark Size meters For MagLog points defines span of the cross marker in meters For Mag pick marks defines size of the mark in pixels For MagPick lines defines width of the line in meters 4 Decimals after dot X Y Controls position representation in the export file If latitude and longitude format is used this must be sufficient value 8 positions to generate a meaningful display 83 Removing polynomial background for profiles and grids 3200 3300 3400 3500 3600 24 35m 37 25 63m 37 TADO reins aes ETa ea ae ra Ree ed OEE A Ed A AR ae enc 7100 OSUNA 25 70m 37 26 18m 37 26 08m 37 23 61m 40 aes eee eure ote eee E EEA ter ant ETE ng n E EEEE EEEE EEE EES 000 i 23 70m 40 o 900 E a f a 26 46m 41 26 76m 41 26 24m 41 26 83m 41 26 67m 41 6900 A eee ns 2PASOM42 A 24 27M 142 aaan 240m 42 oo 24 50m 42 246im 42 23 43m 42 S900 E 38 BE 7
238. k Export picks b Save at EXPORT Export polylines Preview Picture export gt Close Close All Exit Recent Files Figure 15 Profile load using templates menu which should match to one of the templates presented below and reside in the same folder Opposite to the list file multiple folders file selection is not supported File selection dialog may look like figure 16 After all necessary files are selected press Open to advance to the next step see figure 17 This dialog figure 17 is similar to the Simple Load dialog However all data fields are defined by the template not by the user The user should make sure that selected template indeed matches his or her data The following controls are available 1 Add template Press this button to use previously saved list file as a template The user is prompted to locate the appropriate list file Note that only column specifications are taken from the file data file name and UTM information is going to be replaced with the appropriate values After the file is selectedthe user is prompted to enter a unique template description to help identify the appropriate template in the future 2 Remove template This will simply remove a template from the list If you wish to undo this operation you need to discontinue data load by pressing Cancel 3 Set all default templates This option removes all templates from the list and replaces them with stock templat
239. known They can be estimated if at least two sets of data with different orientations of the object were measured For each orientation total magnetization of the body can be estimated as it is described above It means two vectors J and J are know Both of them have an induced and remanent part J VKF earth F Wes JP VKF earth J remon Here Xy 18 the unit vector along the remanent part which has to satisfy norm con ition mL Praga with norm conditions we have 8 equations and 8 variables K Jn This system can be solved as the following z rem rem ec J J 2v J Hearth J i Tiearth 1 fs z Jrem Saige p22 2vK J earth vV The periods in the equations denote scalar multiplication This is the way susceptibility and remanent magnetisation can be estimated 17 4 Mass estimation Given the total magnetization of the sphere k and J em one could estimate the mass or volume of the body The following system must be solved J VKF earth F JremVHrem Here is the same norm condition as above ii em 1 There are 4 equations and 4 variables have to be estimated These are volume of the body v and three components of the remanent vector direction This equation can be reduced to x Jn 2K 4 Fearn J 0 This is a square equation for v and can have positive or negative roots It also may not have any roots In the case when there are no roots the v value which coincides with extremum might b
240. l depth 1 m Figure 162 5 attempts to find a dipole 230 Tutorial Zinital X Y Z J total mass 1 8 51 10 23 1 93 8 5 x 10 266 0 1 8 51 10 23 1 93 8 5 x 10 266 1 10 8 51 10 23 1 93 8 5x 10 266 1 5 8 51 10 23 1 93 8 5x 10 266 0 0 5 8 51 10 23 1 93 8 5 x 10 266 0 Table 4 Results of different attempts to find a dipole 3 A solution based on profile data So far we have used only an interpolated magnetic map to find the position of the dipole Generally speaking this map is not always true If the spacing between data points is large the interpolation procedure fills in the cells in between These interpolated values may not reflect the real behavior of the magnetic field However these values will be used in case of grid based interpretation As you already know MagPick allows you to read profile data It also can use the profile data for finding magnetic dipoles To investigate this do the following Load file bomb grd Go to Profiles Load list and select file bomb_bot 1st 19 profiles line are loaded Redraw the picture to see the profile lines Now go again with the zoom and enlarge area with corners 4 4 14 16 as we did before In a new window go to New and choose All profiles in the window Note that all profile lines in your map window become red T
241. l source were requested shortly These new features were implemented in the framework of MagPick in the autumn of 1996 and Hamburg airport data was reprocessed Each place of interest the user could automatically estimate positions of sources which were represented by set of uniform magnetized spheres To check quality a synthetic magnetic field was calculated and compared with the observed one At the same time attempt was made to estimate the mass of the sources The problem of mass estimation is quite complex A knowledge of susceptibility K and remanent magnetization J is required but these values have a very wide range for ordinary iron Further development of MagPick was resumed in November January of 1997 1998 Many new features were implemented e Regional magnetic field was taken into account as linear function of coordinates This allowed usage of the program directly on measured magnetic field without subtracting the Earth s main field e The results of inversion were presented as an electronic table worksheet Some simple forms of manipulation such as deletion reading undoing etc were implemented e Additional information in the form of lines polygons annotated points clips can be drawn on the top of the magnetic map e Presentation of the field by annotated contours was developed 11 History and features of Magpick Option to load initial profile measurements and plot their geometrical positions on the
242. l the features of each profile his mode is recommended for zooming because you always can easily undo it 2 Fixed scale Here scales 1 e how many pixels per nT in the vertical direction and how pixels per meter in the horizontal direction are fixed and size of canvas is adjusted to these scales This way you see all the profiles with the same resolution and you are able to feel space and field span In some cases 1f you set your scales for a short profile and then load a long one it can lead to a noticeable memory consumption This mode is not recommended if you zoom profiles Zoom automatically changes scales and limits therefore when you undo zoom it can create a very large picture Following is a full explanation of all the controls for the Profile view parameters dialog box gt For large profile sets some time can be needed to find profile you pick 47 Basic operation of MagPick E Profile view parameters Profile graph layout jaga054 Data limits Xmin 11084 93 Xmax 11278 39 Data limits F Draw X grid Xgrid 10 0 e X autoarid 7 Dyaw T grid Tgrid 10 0 l T autogrid Ale 0 2427 X scale 0 2426 ok ize Cancel Figure 19 Profile view parameters 1 Field limits Top and bottom of the view in nT If 3 is checked program automatically chooses these values based on the data 2 Horizontal axis limits Left and right limits of the view in m If 3 is check
243. labels have different sizes the most obvious example is contour OnT On figure 117 you can see result of export for stack plot If you are viewing this manual with Adobe Acrobat zoom into the picture to see small details This drawing also includes line file ma genta see Drawing and clipping on top of the map 167 Export and printing Contour example Figure 116 Example of DXF contour plot 168 Export and printing x io io a N x a PS N E M on w m o 5 5 M a A u a g 2 2 N 3 E 3 7 7 A sD so so so xD sD Ko sD oO X x x y x pi P y x o o o o o o o o o 2 2 2 2 E E 2 2 e di PESTE RARE La T T e as ee 7 i i i i 1 i i i i i i i i i i i OP ZEGEsbL die 4 A tee eae ASZESEIL i i i i i i i i i i i i i RI A N Co ee 0S SE SE JL i i P i O i Q vo6E sesL p i 6L BE SEIL Y i i U i i fo i Te EE ay cool Chon ds id 802 y SEsJL i i q i O i A a IA ES eon nn E Sp SEsIL a i i e i X 16 8y SE Z a ah a E FBP SEIL Ld i i i i i i 0ZZS SE i A inn i i i i i i i i i i i i i i i ARAS o i a grec i o dl 10 46 26 52 10 46 23 2 10 46 20 02 10 46 10 26 apnyi307 Longitude Figure 117 DXF stack plot with magpick 169 Export and printing 22 2 Export to Google Earth Starting with version 3 05 MagPick exports maps directly into Google Earth GE software To use this feature the data must have been
244. ld be used if non standard central meridian is used It saves more information than simple UTM option including ellipsoid parameters Below is 1istgeo dump for the file saved with Transverse Mercator information Geotiff_Information Version 1 178 Export and printing Key_Revision 4 Magnetic map picking Options Opel File Edit Inverse Open Save Profiles Open pick Save pick Pick export gt Preview Picture export Close Close All Exit Recent Files R Postscript Figure 127 GeoTIFF export menu Projection type No projection plain TIFF Export as Transverse Mercator Local system only Local with Xfalse Yfalse IV Create TFVY world file Geotiff parameters xj TIFF compression Law y Length units local only Meter Y Figure 128 Possible GeoTIFF options 0 2 Tagged_Information ModelTiepointTag 2 3 0 0 0 393184 312 4360765 5 0 ModelPixelScaleTag 1 3 0 0499889441 0 0499279872 0 End_Of_Tags Keyed_Information GTModelTypeGeoKey Short 1 GTRasterTypeGeoKey GeographicTypeGeoKey GeogSemiMajorAxisGeoKey Double 1 GeogSemiMinorAxisGeoKey Double 1 Short 1 Short 1 ModelTypeProjected RasterPixellsArea GCSE_WGS84 6378137 6356752 1 GeogInvFlatteningGeoKey Double 1 298 25722 ProjectedCSTypeGeoKey Short 1 User Defined 179 Export and printin
245. le target MagPick can assign initial position automatically see option seed below 5 From the profile view call menu selection Inverse Run Ctrl X This will display inversion dialog and then run inversion User can bypass this dialog using keyboard shortcut Ctrl X assuming all dialog parameters are the same If picks are used as initial positions dialog is always displayed Note that some of the values in the inversion dialog are experimental and rarely used 121t has to be pointed out that in this procedure TVG is treated as 2 sensor array and not gradiometer 149 Array inversion 10 11 Inspect observed and synthetic field on the profile view They should closely match each other Also inspect reported position and depth of the target Delete target in case of bad data fit or inrealistic estimated parameters Proceed with all anomalies in the survey It is typical that anomalies from the different lines would cluster in the area where target is The user can keep this cluster or select strongest anomaly from the cluster using Remove in proximity feature of the dipole spreadshee gt Sort targets in the worksheet as needed i e North to South etc Use direction feature on the map and Inverse Sort worksheets menu on the map view Export data into CSV file to be used by another application and to include into report If the protocols are recorded during inversion user can create individual anomaly plots
246. length of the gap under Distance enter field to use this feature If data file has a special column to mark line change MagPick can use this column for line separation Change in content of this column indicates line change For example to mark line 1 you can have 0 in line column to mark line 2 1 and to mark line 3 0 again Go to Split and select LINE Press Ok and press Ok once more A question appears Append to previous profile list The problem is that we already have load some profile data Now MagPick wants to know do we need keep the data in memory or discard it Answer No and the old profile will be taken out Please note for future if any views of old profile data are currently opened MagPick will not discard old data The loading operation will fail until you close all profile windows Now MagPick shows that it has loaded the 51 profile Press Ok Viewing of profile data Go to File New and choose Profile view in the dialog box You will see just an empty screen with a red vertical line on the right side This is because by default MagPick shows your data as T x here T denotes the data x x axis But lines in g 858m dat are elongated along Y To the change view to T y go to Parameters Settings and select Type Along Y list box at the left bottom corner of the dialog Press Ok Now you can see correct graph of the data as function of x axis The status bar at the bottom of the window shows the type
247. les Ok Cancel Figure 65 Analytic Signal dialog When the Ok button is pressed the program computes the analytic signal and optionally loads results Click Redraw map use context menu after the operation is complete There will be an error message if any of profile views are opened at that time Close them and rerun the computation As soon as Quasi Analytic signal is computed it can be plotted as a stack profile gridded data etc Note that it cannot be used for dipole inversion 99 Simple magnetic anomaly positioning 11 Simple magnetic anomaly positioning One of the simplest methods of magnetic interpretation is position recording for magnetic anoma lies of interest The recorded position must be expressed in convenient units such as Latitude and Longitude in some cases they need to be formatted as degrees and minutes or degrees minutes and seconds or UTM in some cases with false Easting and Northing to keep the numbers manageable The results can be used later to navigate to the recorded anomaly location for further investigation or retrieval attempt MagPick has tools for direct conversion from picks on the map into worksheet of positions as well as direct picking using profile information Those are discussed here 11 1 Convert picks into targets grid operation Picks that are present on the map can be converted into target location and formatted into a worksheet Suppose user sets some picks on the m
248. limits of the window The same types of presentation are possible Opposite to profile view program does a local copies of profiles and makes all profiles active This means that they can be viewed simultaneously on the same coordinate axis As its name implies this type of view provides an inversion You can have only one profile inversion window opened for each map window Operations with the global profile list will not be reflected on it After profile loading the bottom items of the Edit menu of map view become available They allow basic operations e Direction Create a local axis on map view Show the beginning of the axis click left mouse button show direction and click again An arrow is drawn on the screen Then you create a profile inversion view window you are able to view profiles projected on this axis You can dynamically alter the profile view by pointing new axis 46 Basic operation of MagPick e Pick profile Making profile active inactive Show the profile and click the left button If mouse pointer is close enough to the profile line profile is highlighted and profile views if any updated If a map window has a child profile inversion window this action reflects only on the child If the profile was currently active it becomes inactive and vise versa In the case when the map window does not have a child window the profile you pick becomes active and the current active profile is deactivated In that last
249. line only They do not go away from this line when you change lines 5 Another approach to grid profile data You can see from the map we have just interpolated that some anomalies appear as wide points on the profiles They do not look realistic This is a property of the interpolation method the interpolation problems are generally quite complex and might be improved by tuning parameters in the interpolation box You can try for example different values for Tension Tension 0 corresponds to a minimum curvature solution and the value 1 gives a harmonic solution Reasonable values are about 0 25 0 8 But there is another way of interpolation as well We can triangulate data points and then do linear interpolation inside triangles to find data value for each grid point MagPick provides this way also You will see how it can be done In the profile view window go to File Interpolate grid Triangulate The dialog box Triangu lation parameters appears on the screen This dialog has many parameters Here is what to do next e Under X parameters check Data limits This means that the horizontal extent of your grid will be taken in accordance with minimum and maximum values of X coordinate in the data e Under X parameters set interval 0 25 This is your grid cell size along X axis in the grid we are going to interpolate e Under Y parameters check Data limits This means that vertical extent of your grid will be taken in accordance with
250. livers best fit is accepted as solution 151 Array inversion 8 10 11 12 13 14 15 Source depth Imposes depth constrain on the target which affects XY positions This might be useful because would deliver better results if it is known that target is on the sea floor or at some certain depth Possible selections are 1 Variable estimate Let program estimate depth This is most widely used option which delivers depth estimation 2 Fixed to the sea floor Target depth is not estimated target is assumed to be on the sea floor This option requires altimeter 3 Fixed constant Target depth is the same as its initial depth Note that meaning of the depth such as below sea floor from the water level and from sensor depends on selection How to report depth below Source type Select object type as dipole s monopole s or free dipole s First and last se lections are the same but free dipole is experimental type of inversion which does not require orientation parameters such as Earth s field inclination and declination The down side is that dipole magnetic moment cannot be estimated It should yield similar ot even identical results to the dipole Background defines how to approximate Earth s and geological fields Possible selections are DC constant Linear ax Tj or square ax bx Tye The last is considered more universal Source seed defines how to assign initial XY position for i
251. ll be used in this case it does not make sense because there is no real map data If you start it from All profiles in the window then the profile data is used This is what we want All profiles window 1s a counterpart to the map window There is just only one allowed per one map window Look at figure 165 There is a map window on the right side of the screen and a profile inversion window on the left side From a map window go to File New and select Profile inversion A new window pops on the screen and all your profile lines in the map window become red You are now seeing all the profile data in your map window as graphs T x To adjust view do the following In the map window go to Edit Direction Draw direction as it is shown on 3 Click first point move to the second and click again Arrow is drawn e In the profile inversion window go to Parameters Settings choose type Along pointer and press Ok Now you are able to see all anomalies from pipe at the same place They were projected on direction you have shown e Change range for profile inversion view If you draw an arrow like it is on figure then in the profile inversion window go to Parameters Settings uncheck here for Xmin Xmax Data limits and enter Xmin 100 and Xmax 100 Now the horizontal axis extends from 100 to 100 m Constraining data used for locating We definitely do not want use all data presented in the map window for location of a single pipe
252. loaded back into MagPick Start new copy of the program or close all the windows in the running copy of MagPick and go to menu File Profiles Simple Load Type in false Norting and Easting as it is shown on the screen shot in Figure 159 211 Coordinate transformation using Corpscon software l0 x Office Otfice Project Project Remark office Project 21 July 2008 INPUT OUTPUT Geographic N4D83 State Plane N4D27 1702 Louisiana South U S Feet Accuracies of conversions from NAD 83 to NAD 27 are typically 12 to 18 em 90 69768100W 282 282 Latitude 23 93998400N Horthing Y 99872 936 Longitude 90 697638100N Easting X 2203375 201 Convergence 0 19 04 36756 Scale Factor 1 000095760 Datum Shift m J Delta Lat 26 260 Delta Lon 8 899 Remark Corpscon v6 0 1 U S Army Corps of Engineers E Close Figure 158 Corpscon conversion output window Now press Add button and select the file created by Coprscon Assign the proper groups see 5 5 for details how to load profile files For Split select Line for X select 1 Longitude assuming file header was not edited for Y select 2 Latitude for Data select 5 T Depth and Altitude are fixed if they are not good otherwise select appropriate boxes Use Time and Date Under UTM parameters select NO UTM Load data as usual Because there was no UTM transformation data in the projected system and false Easting and Northing were used in the abov
253. lowing columns 1 7 8 X Y horizontal position of the cable point Can be presented in short or full projected coor dinates such as UTM or Latitude and Longitude Z depth Depending on the following field can have different meanings such as depth below sea floor burial depth from the sea water level w level or from the sensor sensor Z ref Vertical reference Can be burial w level or sensor Fit Least squares difference in nT between observed and synthetic fields The smaller value is the better Mass A Estimated electrical current amperes Discrepancy This is goodness of fit similar to the fit above but not depending on anomaly amplitude The range is 0 100 The acceptable values are above 80 Amplitude nT This is anomaly min max difference in the part selected for inversion Count Used if results has been clustered 1 otherwise ISNote that these results are not dipoles 139 HVDC cable inversion 10 11 12 13 14 15 16 17 Object Object type such as DC PAIR Single Dipole etc Sensor depth taken at the polyline and profile intersection Sensor Altitude The same but altitude Line Survey line name Date and Time This value is taken at the polyline and profile intersection Channels Channel used for inversion DX DY DZ DM doubles of standard deviations of X Y Z and current estimates These values only take into account fit b
254. lse northing and easting during profile reading e Make sure of the UTM parameters you are using This includes false northing and easting It 1s better 1f you write them in a file and keep with the data e After the profile is loaded make a grid This grid will be related to the local short UTM system e Set up UTM transformation in MagPick exactly the same way as you used for the initial pro jection Go to Options Utm setup and proceed 122 Earth s magnetic field model IGRF Figure 81 shows the UTM setup dialog in Magpick You should specify an ellipsoid name di rectly enter the ellipsoid parameters if your ellipsoid is not listed central meridian scale factor normally 0 9996 for UTM 1 for Gauss Kruger and false northing and easting For your conve nience an easy check UTM calculator is provided Using this tool you can convert Lon Lat coordi nates to Northing and Easting and vise versa It is recommended to use pair of points with known UTM geodetic coordinates to check your setup before going to work with whole data set Knowledge of the central meridian or zone number is one of the problems using the UTM system Six degree zones start at 180W and go to 180E Magpick allows you to find a zone central meridian based on your data The following shows how to proceed e Check Set central meridian from first sample e Go to UTM calculator and enter Latitude and Longitude of your location e Press Lon Lat gt UTM Read Nor
255. m just uses middle point between markers as target location and half of the dis tance between marks as depth which can be reduced to the sea floor or water level 1f altimeter and depth sensor are available No amplitude is reported except at marker s position The tar get is reported in the worksheet as TRIVIAL For multiple channel data pick is applied to the channel entered in the dialog For trivial picks program does not report the shape of the anomaly 2 Intelligent pick Program tries to guess shape of the curve enclosed between markers positive or negative monopole or dipole and estimate amplitude by computing minimum and max imum in the enclosed area The recorded target is marked as M negative monopole M positive monopole or D dipole Target location is selected on the maximum or minimum for monopole or on the maximum slope for dipole The target type is set as Intl intelligent The example is shown on figure 68 3 Approximation pick In this case program uses 2D inversion see seciton 17 5 to approximate field between markers 102 Simple magnetic anomaly positioning 6080 6100 6120 6140 45290 z325 re 3 45290 45280 basa l E 45280 Ea pa Ea a 5950 6000 6050 4 784854 12 3116100 49 17 05 M 2 784867 02 3116001 27 32 53 3 784784865 811616541 2 47 Figure 68 Setting markers and picking target location from the prof
256. map it is marked with letter G grid Z is half of the pick length This is a very rough estimate of the depth to the source Program also reports field amplitudes at ends of the pick The rest of the worksheet is set to zero User can modify worksheet contents by using context menu right mouse click see also figure 66 Worksheet information can be saved into and loaded from the text file User can remove individ ual targets or clear the entire worksheet Most important functions are Format positions and Export Format positions works pretty much the same as the status line dialog does When selected the following dialog is displayed figure 67 Position format x Position format Decimals 6 Short UTM Digits after dot 2 Full UTM Lat Lon Ok Cancel Figure 67 Possible position formatting Here user can select what to display and how to display If data is not in UTM them Short UTM must be selected If data is in UTM then there is a choice short UTM Magpick internal units or full UTM with false Northing and Easting taken into account Last is Latitude and Longitude Format 1s also user selectable and can be decimals degrees and minutes degrees minutes and seconds Note that you need to set enough decimal places digits after dot if you wish to present positions in Latitude and Longitude The second useful function is Export Note that data are exported as they are displayed in the worksheet I
257. map magpick File Edit Inverse Options Operations Profiles Window Work s Dipoles Pipes Run Targets Run batch Inversion folder Pick into targets Remove results gt Sort worksheets Align pipelines Figure 137 Menu item to select Inversion Folder If inversion folder selection has been changed or lost use menu Inverse Worksheet Inversion folder to point MagPick to the correct location Selection dialog itself looks like the one shown on figure 138 24 3 Create targets profile plots From the dipole worksheet menu call File Plot Inversion Graphs menu 139 Plot dialog is displayed as shown herg140 Make sure all three paths are set correctly Use buttons to modify these values 1 Gnuplot executable file with path This is the place gnuplot exe file resides Note that win dows version with name wgnuplot exe is not used only command line version gnuplot exe is 192 Anomaly plots with gnuplot Browse For Folder Please select a folder Use Make new folder button to create new folder if needed z data E do adu_dhabi 4 01 05 12 de GPX de saudi e Fielddata de new pictures de originals Ho patcht Lo protocols Figure 138 Inversion Folder selection dialog needed By default program will use C Program Files gnuplot folder or C Program Files x86 files Under Linux it s just enouth to type C gnuplot
258. may fail or the program even crush in that case Because of that it is recommended to process data with a filter before building a triangulation network a om E E E E E E m a E E E n m m E E E o E E C H L a a P E E E a a m Original data Filtered data Figure 22 Illustration of data filtering Squares represent original data and circles the result of filter ing All data points inside one grid cell are replaced with one point Refer to figure 22 to understand how data filtering works It affects data points inside one grid cell of a new map All these points are replaced with one point located in the middle of the cell The following are options for data value e Simple average of all data points inside cell is calculated and assigned to the middle of the cell e Median value of all data points inside cell is calculated and assigned to the middle of the cell This might be better when data has considerable spikes e Point nearest to the middle of the cell is taken other points inside the cell are ignored This procedure greatly reduces amount of data being triangulated Note that this idea is similar to the blockmean program from GMT package 3 6 1 2 Gridding with splines This feature employs a method developed by Smith and Wessel 3 which is an enhanced modification of the minimum curvatur
259. minimum and maximum values of Y coordinate in the data e Under Y parameters set interval 0 25 This is your grid cell size along the Y axis in the grid we are going to interpolate e Check box Filter data recommended This means that before triangulation the number of your data points will be reduced If a few of initial points fall into one grid cell only 223 Tutorial one will be taken or some combination of points This is recommended because if data has duplicated points there will be a problem the program even can crash Set Method as Average value and Format as GS ASCII e Finally change the file name to g 858mt grd where t stands for triangulated This is a bit faster than spline interpolation We end up with a file g 858mt grd on the disk Now again go to File New and select Grid view In the empty window you can check settings in Options Settings and Options Size or go directly to open and pick file g 858mt grd you do not need to close your old map view Compare these two pictures Draw stack profile Up till now we could see the profile data in a separate window Now we will combine the profile information with a map to see them simultaneously In the map view go to Options Settings Click two times on Show profiles till window Profile plot parameters appears on the screen Inside this dialog e Check Show profile direction and set each 200 pixels This will allow MagPick to show the dir
260. mith Steven M Schweda Christian Spieler Cosmin Truta An toine Verheijen Paul von Behren Rich Wales Mike White This software is provided as is without warranty of any kind express or implied In no event shall Info ZIP or its contributors be held liable for any direct indirect incidental special or conse quential damages arising out of the use of or inability to use this software Permission is granted to anyone to use this software for any purpose including commercial ap plications and to alter it and redistribute it freely subject to the above disclaimer and the following Copyrights restrictions 1 Redistributions of source code in whole or in part must retain the above copyright notice definition disclaimer and this list of conditions 2 Redistributions in binary form compiled executables and libraries must reproduce the above copyright notice definition disclaimer and this list of conditions in documentation and or other materials provided with the distribution The sole exception to this condition is redistri bution of a standard UnZipSFX binary including SFXWiz as part of a self extracting archive that is permitted without inclusion of this license as long as the normal SFX banner has not been removed from the binary or disabled 3 Altered versions including but not limited to ports to new operating systems existing ports with new graphical interfaces versions with modified or added functi
261. mon plot header and font size All these items have default values if you do not call Title for given window Caveat If you are printing to the file you may encounter a problem When you open Preview the second time your first postscript file is truncated to about 100 bytes To avoid this change name of the file if you want to keep this file before you call Preview again 6 Grid operations Magpick allows you to create and modify grid data loaded in a variety of ways which are available under Operations These features are under development and will be extended in the future 6 1 Making grid out of profile data After the profile data has been loaded a regular grid map can be created There are two methods available gridding with tension by B or by triangulation with linear interpolation 4 There are a few places where gridding procedure can be started Originally it was located in profile view under Files Interpolate grid but because of obscurity it also available under map view Profiles Interpolate grid Here is a basic sequence of operations to make and view a grid e Start MagPick and load profile data Use the profile list or Easy profile load see 5 5 2 Note that you can load few profile lists or use easy load few times by appending new profile data to dat tat is already loaded After you complete this operation MagPick maintains the profile data internally e If your primary goal is to make a map go to Pro
262. n library version 244
263. n the map 231 Tutorial Now go to the profile inversion view and set Parameters Settings Type along pointer See how the picture changes You are now seeing projection of your data on a direction you have shown on the map view Zero is where arrow on the map view starts it is marked by small o Now go to the map view and show another direction do the same as for first arrow The profile inversion veiw updates automatically to reflect a new horizontal axis Return now to Type Along Y e In many cases we need to constrain the data we are going to use for an inversion For the map view we did it by zooming part of the map For the profile view we have a more flexible way Select Edit Polygon in the map view menu now Go approximately to point 6 5 6 and click Then go to 6 5 14 click 10 5 14 click 10 5 6 click and again 6 5 6 click We have drawn a polygon in this case a rectangle Check the profile inversion view now The data is cut Only this piece would be used for the inversion If you pointed polygon vertex by mistake you can undo this operation by clicking right button If you need to get rid of the existig polygon just go to Edit Polygon one more time The polygon contour will disappear It is time to work on the inversion itself Make a pick on the map view It will serve as initial location for the magnetic dipole Go to Inverse Run in the profile inversion view Here is a dialog very similar to the one we already had
264. n this limit estimation procedure stops Initial depth Initial depth for the whole dipoles Sometimes the estimation procedure can be sensitive to value for instance it can put dipoles above observation level In that case take a new value and repeat Density If you want a mass estimation the density value is needed For instance if suscep tibility is in CGS units and remanent magnetisation in gauss and you want to have mass in kilograms it should be the mass of one cubic centimeter in kilograms J scale In many cases the mass estimation will fail MagPick estimates the total magnetic moment of the dipole in cgs units anyway Because it is known that 1 ton of iron has dipole moment in range 10 10 cgs a rough method of mass estimation can be applied Just put the appropriate scale factor and Jota will be in the mass units Induced only If you guess that the body can have only induced magnetisation check this box It is means instead of three components of magnetic moment the program estimates only one because the direction is known Mass estimation becomes trivial then Linear solution only In some cases you can presume that you know the source location and you wish to find only magnetisation Then check this box The program will not do iterations because the problem is linear Grid type This is the format of output synthetic grid file There are two choices Golden Software ASCII grid and netCDF binary grid The last one
265. n vary Then each line describes one point The first word could be UTM or GEO X and Y coordinates in the same system as data are follow The third number is the size of the mark on the screen in pixels Zero size produces no mark The color name can be chosen from the set above The rest of the string is optional text which appears near the mark The mark itself has a shape of with the hot spot in the centre Polygons This allows you to draw filled polygons to obscure part on the picture The file has exactly the same format as the line file MagPick joints first and last point of each line to make a closed polygon Specify the color you you wish The pen width should be zero to fill in required area only Clip MagPick does not do real clipping as PostScript does Do not confuse this type of clip ping with grid clipping Grid clipping changes the data this feature draws a white polygon of complex shape to simulate clipping of the picture The clip file itself has the simplest for mat it s just two columns of the numbers The first pair of numbers should coincide with the last pair to have a closed path The order of points is very important The points should go clockwise see figure 1 1 1 data boundary magpick drawing to simulate clip Figure 11 Clipping polygon Here numbers inside the contour the show order in which the clip path must be specified Note that you should start with minimum
266. n without linear term a x xo Tac If amplitude box here is checked and absolute value of amplitude is below the limit result is not accepted and warning is posted unless Post no warnings option below is enabled Use depth constrain Allows to reject target based on acceptable depth interval Note however that because this type of picking is just an approximation reported depth is at best just a distance between sensor and the target measured along the straight line Therefore wider range is recommended to avoid unnecessary rejections Use discrepancy constrain Use quality of fit measured from 0 worst to 100 best The value of 80 is recommended to avoid stray picks Post no warning if not accepted Typically program shows warning window with explanation why pick was not accepted listing all causes To disable this window please check here and picks would be rejected silently 105 Geographic projection transformations UTM and PROJ 12 Coordinate transformations 12 1 Basics MagPick is developed to work with planar coordinates preferably expressed in meters However this is not always the case modern data typically recorded with the GPS This leads to two possible scenarios of data import 1 Original case Data is recorded using local coordinate system Typical examples are simple and mapped G 858 859 magnetometer survey modes where coordinate system is marked with cones or stakes on th
267. ncy Jo a gt 100 Ok Cancel Figure 125 Exporting drawings into Google Earth 5 Position annotation Selections are Balloon only or Show on the map In the first case anno tation is only displayed when user clicks on the point In second case annotation is displayed directly on GE background Position is always displayed in the balloon 6 Google Earth folder name Folder name for GE 22 3 Export into BMP file This is simplest type of picture export available in Magpick All contents of the map window are simply saved into Windows BMP format Because no compression is used the resulting file can be quite large Resulting file could be easily loaded in standard windows applications such as Paint 22 4 Export into TIFF and GeoTIFF formats MagPick allows saving content of the map window into TIFF GeoTIFF formats This function pro duces a compressed image file and therefore has advantage to simple BMP export Besides GeoTIFF allows embedding positioning information into the image so it can be used later on in GIS systems You can learn more about TIFF Geotiff formats from the following URL http www remotesensing org libtiff To access GeoTIFF export use File Picture Export GeoTIFF menu as it is shown on figure MagPick shows the choice selector shown ob figure 128 The following selections are possible 1 No projection plain TIFF If this option is selected no georeference information is embed ded in the
268. ne to accept your profile shifts of we j xFalse 2200000 00 YFalse 98000 00 as project coordinates UTM shifts Note it is recommended to use short coordinates in MagPick Figure 160 Program asks to use false Easting and Northing as UTM shifts easily by re loading the data If procedure is done correctly there should be no problems Go to Options Status Line menu to make sure that full or short UTM is selected and the string format is in decimals Click OK Now look at the status line at the bottom left corner of the screen as you move the cursor over the map area The numbers should now be in State Plane Continue working as normal till you need to export map as GeoTIFF format Go to File Picture export GeoTiff menu Select dialog options as in the dialog 161 With this selection GeoTiff file is prepared in the State Plane coordinates even data is loaded as truncated State Plane additional shifts are added to the file during the export No projection information is saved into the file so it s the user s responsibility to select correct projection in his or her GIS system It is known that if GeoTIFF is planned to be used in AUTOCAD software the no compression option is preferable Option Create TFW file creates additional world file used by some GIS programs Note that all information is already coded in the GeoTIFF file itself user can always create TFW file by free software available from geotiff geotiff html Below
269. netic field for top sensor BOTTOM_RDG for bottom sensor VRT_GRAD difference between them TIME DATE LINE ogical line assigned by operator and MARK X is the x axis and Y is y axis Select them in the list boxes X and Y Now we have to select the data Let s take a bottom reading select BOTTOM_RDG 4 in list box Data The profile view on the map as XY curve can be active if selected by operator and being viewed in a separate window or inactive not selected and not viewed It is makes sense to have different colors for these two conditions Names of the colors you can change under Active color and Inactive color Let it be RED active and BLUE inactive Press Ok Create the profile description dialog closes and you can see that a new string appears in the list box Press Ok Profile data is being loaded as X Y magnetic field Finally MagPick reports 1 profile loaded If you are familiar with magnetic survey design this may seem strange File g 858m dat has 51 lines The problem is you did not tell MagPick how to distinguish data between lines We will now go over how to correct this problem Loading several profiles lines from one data file Go again to File Profiles Simple Load press Add and choose file g 858m dat You see the Split Here you can specify how MagPick is going to recognize end of individual line It can do it automatically by finding gaps in your position data Select Distance and specify the
270. ng dipole model 94 Quasi Analytic Signal omputed with FFT dT dx computed as derivative along the path Quasi analytic dT dx dT dy dT dz Figure 61 Quasi Analytic signal computation 95 Quasi Analytic Signal Total Field Map Analytic Signal Quasi Analytic Central Line Signal comparison o 20 0 20 40 b o 20 0 2 40 o 20 0 20 40 F o 20 0 20 40 o 20 0 20 40 5 6 04 40 40 0 2 n o1 amp 20 20 2 I 20 f 2 h o o D 0 0 0 F 20 20 0 1 0 2 a7 40 40 8 8 o 20 0 20 40 o 20 0 20 40 o 20 0 20 40 o 20 0 20 40 o 20 20 40 EEE DE SE 6 E 3 408 8 08 i 5 6 8 3 808 8 E 8 d 7 28 08 8 8 I 75 3 D 20 x 4 4 4 40 20 o 20 40 o 40 20 o 20 40 40 20 o 20 40 as meters meters meters Figure 62 Analytic signal relatively to the true Analytic Signal at different inclinations of geomag netic field 96 Quasi Analytic Signal This results can be summarized as a rule of thumb in figure 63 showing approximate errors of Quasi Analytic signal relatively to the true Analytic Signal at different inclinations of geomagnetic field Note the similarities in true versus quasi analytic signal contours N Nn Signal Error n Quasi Analytic Nn O 10 20 30 40 50 60 70 80 90 Earth s Field Inclination degrees Figure 63 Relative errors in Quasi
271. nge should permit only this selection e A pair is accepted if its field value in the middle point is in between the end values Note that still after all these limits one point can participate in the different pairs To resolve ambiguity pairs are sorted in accordance of difference between their maximum and minimum fields The sorted list is scanned to create unique pairs To use this feature go to Edit Auto pick select angle distance and field ranges if you want to remove all existing picks made by hand or results of previous auto pick check Remove all old picks Press Ok Depening on size of the map and its complexity the operation will take different times to complete If you checked Remove all old picks you are prompted to save old picks before MagPick removes them As a result you get many anomalies selected It is recommend that you inspect results before going to magnetic source estimation it also can be done automatically for all anomalies by Inverse Run batch Magpick may place some picks incorrectly and you should correct them 5 5 Profile information loading and viewing 5 5 1 Profile loading Besides map processing MagPick allows loading of the profile data The input can be any ASCII file s which has column organisation At a minimum the file should have three columns X Y 38 Basic operation of MagPick coordinates of the point and a value of the magnetic field To make loading and processing faster the
272. nowns are J J2 J3 a b Tac Horizontal position xo can is transformed into X Y plane coordinates using data line direction z is the distance from the profile to the object It can be treated as depth of the target assuming target is just below the profile i e XOZ plane is vertical and reduced to the depth below the sea floor using altimeter reading It also can be converted into horizontal off line offset assuming target is on the sea floor It is not possible to say however on what side of the survey line target is located left or right Magnetic proprieties of the target are indirectly defined by J Jz J3 If we introduce amplitude of the target as J J a J5 53 we can use it to judge about target s mass and to compare targets between themselves because that value should not depend on the measured field amplitude 5 T T T T e magnetic field nT original data 1 approximation 2 monopole part Z27 R 3 dipole part x xg z R 4 other x x9 R 5 Estimated location estimated positio 0 10 20 30 40 50 60 70 80 distance m Figure 88 2D inversion example Dipole monolople and other part of the total field is shown The figure 88 shows example of the real data 2D inversion with all three main terms of the above formula plotted separately The ratio between dipole term x x9 z R gt monopole term z R gt can be used to classif
273. nt floor topography Therefore object could be even partially exposed The target position is shown on the map view ag100 below Note that line 5 shows positive anomaly line 4 negative and object position is estimated as in between closer to line 5 User discretion is always advised when dipole inversion is carried out Unreasonable results as well as results with bad fit should not be presented If dipole inversion fails user should use simple target position option which is essentially just marking the anomalies 143 Single magnetometer inversion Polygon properties Figure 93 Polygon propreties dialog 144 Single magnetometer inversion Profile Inversion Parameters x M Use all default parameters Y Use IGRF for Earth field Source type Dipole s Main field Inclination deg 26 574 Background Square Main field Declination deg fi 376 Source seed Automatic X axis azimuth deg 90 Magnetization 3D Full Data type Profile default y Initial source depth m 20 Sensor separation m fi Sensor depth Spline smoathit y Extendend area Polygon Smoothing parameter 1 08 003 xtension distance m iterations 2000 Try offline locations of length Po How to report target depth From sea floor source depth Varible estimate M Create protocol DAT file in the inversion folder Select inversion folder Figure 94 Inversion dialog for single magnetom
274. ntered over HVDC cables A single infinite current facing out of the page B pair of wires with currents facing in and out C the same as B but with conductors rotated 90 clockwise For simplification Earth s magnetic field considered to be vertical The recorded anomaly is the projection of the lines of force into Earth s magnetic field Earth s magnetic field The figure 107 shows possible HVDC cable signatures Note that in case of two conductors signature depends on orientation of the cable Typically cable is deployed horizontally B but there could be some deviations and possibly even twists in the cable The magnetic field amplitude of a single infinetely long wire is given by 0 2 r T 1 where T is the amplitude of the magnetic field anomaly in gauss 10 nT 1 gauss 1 oer sted i the current in amperes and r is the distance in centimeters between the wire and the point of measurement The field amplitude of two infinite parallel currents at distances much greater than wire separation is 2 di T 0 a 2 r 155 HVDC cable inversion Here T is field amplitude in gauss d is separation between wires in centimeters i is current in amperes and r is distance between wires and the point of measurement in centimeters as well The formula is valid if d lt lt r The Earth s field magnetic field and local geological anomalies can be modeled as a linear term assuming relatively short length of the pro
275. ntouring method can be used Profile XY positions with direction pointers Profile stack plot e User s picks results of inversion polygon and pointer Additional drawings such as lines polygons and points However clip is not included All of the above elements reside on different AutoCAD layers Properties of each layer such as name color and line style are user selectable Each drawing can have its color defined by layer or directly thus allowing the AutoCAD user to change the color of all drawings on the layer at once The DXF file is in compliance with DXF 2 5 specification and works with the following CAD sys tems Autocad release 12 and 13 ItelliCAD from CADopia AutoDesk Volo View Express viewer for DXF and DWG files TurboCAD 2D and FastCad DWG DXF viewer The DXF file does not contain any AutoCAD variables only line style and layers definition tables and entities To match RGB colors in MagPick to AutoCAD pens a standard AutoCAD palette is used In some cases it might result in different color in AutoCAD as compared with MagPick However most af the colors are transferred without distortions DXF export is available in the grid window under File Picture export DXF Look at figure 114 It presents the DXF export dialog box Each layer is represented by the string in the list box Star means that the layer is selected for output The absence of means that the corresponding layer won t be included in the dra
276. number Data type Field Calc Field Decimals after dot for X Y J 31 Is 1 al Decimals after dot for data je 14 CET o UTM parameters M Append Lion host EN N S Create list file to load data Ok Cancel Figure 155 Saving profile data in Lat Lon with W and N postfixes After data is saved start Corpscon under the setup menu select the Input Output tab example e Set Input to Horizontal Geographic 1983 NAD 83 86 and Vertical none Note that 1983 NAD 83 86 is the Corpscon equivalent to WGS 84 e Set Output to Horizontal State Plane 1927 NAD27 Zone 1702 Louisiana South in US Survey Foot vertical none e Click OK Typical Corpscon window for this operation is shown on figure ll adcan Vertcon Geoid Other INPUT OUTPUT Horizontal Horizontal System fi Geographic y System 2 State Plane y Datum fises NAD 83 86 y Datum fis27 NAD 27 y Area 0 None rea 0 None Zone 0 None 7 Zone 1702 Louisiana South y Units 9 None Units i USSuveyFoot y Vertical Vertical Datum 0 None y Datum 0 None Units l Nne Units 0 None y Figure 156 Specifying projection information in Corpscon software 209 Coordinate transformation using Corpscon software User should pick the appropriate coordinate data for his or her state Figure 156labove shows an an example for Louisiana South G
277. nversion Automatic uses middle point between profile markers Use pick uses middle points of the MagPick picks from the map The picks should be created before calling the inversion dialog and positioned where target s are expected Initial source depth Initial seed for target depth Depending on selection below this value could be defined as depth below the sea floor from the surface or from the sensor Note that ctual sensor depth in the water column should be taken into account For instance setting depth as 0 while reporting it as below the sea floor is appropriate but if reporting is set below sea level and total water depth is 8 m setting initial depth as 0 would cause program to converge to erroneous result in latter case 8 is much more appropriate Sensor depth and Smoothing parameter describe how to treat recorded sensor depth Depth can be treated as it is no Smoothing or slightly smoothed with the spline In the first case abrupt variation in depth could cause high frequency noise on the synthetic field because MagPick takes sensor depth into account In case of smoothing smoothing parameter can be entered below The advised value is 1 e 3 The less the value he higher is smoothing thus something like 1 e 10 would yield straight line Iterations Number of iterations for non linear inversion The default of 2000 is never ex ceeded if procedure converges How to report depth This selection also affects initial dep
278. o draw color rectangular behind color scale 4 Move to Back Moves annotation behind other annotations 25 1 Individual annotation types The picture 148 below summarizes all annotation types available in Magpick A Annotation Magnetic field map Magnetic field nT B Color scale 2 0 0 0 20 40 60 80 11 0 140 170190 22 0 25 0 28 0 31 0 34 0 36 0 C North arrows A N MW meters 30 l 1 1000 D Map scales o feet 150 UTM Projection F Projection Ellipsoid WGS 84 E Polygon Central meridian 93W parameters False Northing 730000m False Easting 4280000m 100 nT G Profile Stack H Time stamp _ 04 06 2007 Scale 168 16 15 43 Figure 148 Different annotation types 201 Map annotations 25 1 1 Text annotation label A F H These annotations are available from Add annotation context menu By default annotation text is set to This is test text sentence User must double click on the text and replace text with annotation he really needs By dragging annotation handles user can adjust non transparent rectangular area drawn behind the text Note that size of the rectangular area may not match size of the text so 1t s users responsibility to adjust this for an appropriate size this is also true for some other annotation types Double click on the annotation to call the properties dialog see figure 149 Label properties x V Fill with solid color Fill color M Draw border Border color i
279. o to the Convert User Defined Data File menu Set the following fields e Input File Name Select the dat file saved from MagPick earlier e Output File Name Create an appropriate name and add dat to the end of the file to include proper extension The recommended extension is dat In the Input file the data string is displayed in space delimited form Each column of data has a number starting with 1 at the first column and ascending up by 1 Make Sure to check the boxes labeled Send to output window and Send to output file The output window is good for a quick QC and to estimate false Northing and Easting required by MagPick Typical Convert User Defined Data File dialog is shown here on figure 157 210 x Input Filename C data Eric t dat Browse Output Filename C data E ric t state plane dat Browse Y Send Results to Output Window V Send Results to User Defined Output File Input File Line fao 70430900W 28 93505100N 1 00000000 7 34999990 47624 60546875 1 08 07 08 16 58 59 000 Input Output Geographic NA4D83 State Plane NAD2 1702 Louisiana South U S Feet Hame Point Name Northing Out Easting X Out Scale Factor Out Combined Factor Out Convergence Out Latitude In Longitude In Latitude Datum Shift m Longitude Datum Shift m Input Field 1 Input Field 2 Geo Coordinate Format Geo Coordinate Format Decimal Degrees y Decimal Degrees z 000 0 00000000 mn0 Delimiter Delimi
280. of pair maximum minimum This feature is experimental and will be improved in future Presently is is available under Edit Auto pick The selection algorithm is fairly simple and uses the following steps l ze Find all points which are local minimums and maximums Create pairs maximum minimum The number of these pairs can be fairly large each max imum can be matched with each minimum To reduce number of possible pairs the following user defined restrictions apply see figure 13 e Two points can be treated as a pair if the distance between them is in the user defined range e Two points can be treated as a pair if the field difference between is in the user defined range 37 Basic operation of MagPick Northern hemishpere 60 angle range azimuth min 150 09 Azimuth max 210 00 q S Distance min 0 000 Distance max 4 000 Field diff min 100 000 Field diff max 500 000 gt Remove all old picks 5 4 gt Southtern hemishpere mag field X East ebues pel XEN UIN distance angle range 210 Je Min max distance range Figure 13 Setting parameters for automatic anomaly selection picking e Two points can be treated as a pair if the azimuth from maximum to minimum is in the user defined range For example in northern hemisphere anomalies should have mini mums located north from maximum therefore the azimuth ra
281. of the color image When you are ready press OK button You will be prompted for file name Enter full file name with extension PDF 22 6 3 Including MagPick PDF graphics into OpenOffice and MS Word documents as EPS files It is highly desirable to include MagPick maps into office applications such as Microsoft Word and Open Office This can be accomplished with help of additional software available from the Internet The prerequisites are e Post Script or PDF printer should be installed for MS Windows systems Examples are Free PDF CutePDF writer and Adobe Acrobat Writer It is also possible to configure one of the standard Windows printers such as Apple Color LW printer to output a Postscript file 184 Export and printing x Property Value EncodeColorlmages false Not defined true SubsetFonts MaxSubsetPct ConvertCMYKImagesToRGB4 AutoFilterColorlmages ColorlmageFilter EncodeColorlmages Cancel Help Edit lil Page Offset pt x fo le jo Now Figure 131 Disabling JPEG compression in PDF e pdftops command line tool This is the part of XPDF program It is available as part of Cyg win distribution that can be downloaded from http www cygwin com and also as a native win32 executable This tool is required to convert a PDF file into EPS format epstool command line tool This program is native to Linux but is also available as win32 executable from numerous FTP sites The s
282. of the data was collected with a DC offset The latter can happen if part of the magnetic data was collected at a different time with different Earth s main field Linear transformation is available from the profile view window under Edit Linear The dialog box is very similar to one for smoothing There are few controls e Choose what to transform All profile data active profile s or if there are two valid markers on the same profile between marks can be chosen e Choose the color for transformed curve The result of scaling will be displayed on the same axis till you Accept transformation 68 Profile data transformations e Enter data scale a and data bias b These are the most important parameters Please do not enter a 0 it will turn all readings into a constant If you want just add a DC offset enter a and b equal to DC offset you want e In case of multi channel data transformation is applied to one channel at a time Enter the channel number under Channel to apply In many cases only one channel this value is 1 After you press Ok button Trew is displayed on the same axis as Toza This gives you a chance to check that everything is right After you satisfied with the result you can replace the original data with new data Go to Edit Accept and pick what you need This dialog also is used to accept smoothed data If you don t need transformation result go to Edit Discard If you want to restore original d
283. of view T y It also shows Y and T values at the current mouse location 219 Tutorial Go to Parameters Settings again and set Type Along profile Now the horizontal axis shows the distance along the line line may not be straight This distance is always positive and starts with 0 Checkbox Shrink to canvas is responsible for the display method If it is checked then Y size and X size vertical and horizontal sizes of the canvas stay constant when you change your profile The profile data gets scaled to these fixed sizes If it is not checked then T scale and X scale parameters are used to find the appropriate size of the canvas to accommodate the data In this last case vertical and horizontal scales of the data stay constant when you change profiles You can see difference between them in the same scale Set Y size as 500 and X size as 1000 Notice this is how we can zoom data We also can zoom data the same way we did for maps Go to Edit Zoom Then press the left button and drag mouse to select area Instead of creating new window graphs are zoomed in the same window To unzoom just go to Edit Redraw This kind of zooming works best when shrink is checked Browsing profile data There were 51 lines but we see just only one To see other lines go to File Browse The moda less dialog window appears with all your lines with string numbers from the file Press but tons gt gt and lt lt picture will change
284. offset with dragging Shift along profile 250m to the right 20 m Drag profile 250m to the right 20 m 3250 3500 3750 4000 4250 4500 4750 5000 3250 3500 3750 4000 4250 4500 4750 5000 5750 5750 5750 5750 5500 5500 5500 5250 5250 5250 5250 5000 5000 5000 5000 3250 3500 3750 4000 4250 4500 4750 5000 3250 3500 3750 4000 4250 4500 4750 5000 Xm Figure 36 Example of calculating magnetometer offset with simple shift and dragging Goal Let s consider the object magnetometer fish being dragged behind the boat with constant and known tow cable length The boat is equipped with GPS receiver and therefore its position is 75 Profile data transformations known The task is to provide a reasonable approximation for the magnetometer fish position based on GPS readings and the cable length Solution This solution is an approximation and does not take into account a 3 D configuration depth and some physical effects like friction Nevertheless it gives reasonable behavior even if ship makes a turn We assume that we know the position of the ship A and the magnetometer fish at time t N see fig as well as the cable length At time t we know the position of the ship B but do not know position of the fish M To find the fish position we draw a stright line NB between the old fish position N and new ship position B Then we use a straight line from B to N and place the fish at a cable length
285. ofile parameters 1 Show profile direction To see how data was taken MagPick will show your profile direction estimated from the samples order in the file note that if your file has time reversed it would be opposite Check this box to see the profile direction 2 Interval between signs Interval in pixels to place the sign gt displaying profile direction Distance is taken along the line This value can not be less then 20 pixels If less then 20 very dense marks appear Recommended is 100 200 pixels 3 Plot stack profile This box should be checked if you wish to see a stacked plot If not checked the rest of the controls in this window are disabled 4 Datasets to draw Each profile file can have several datasets inside Thus the word profile does not mean a sequence of X Y Z field values but X Y Zi field were i is the dataset num ber You can select which data set you wish to see as a stack plot 5 Data scale Data has to be scaled to be plotted together with coordinates This value is needed to scale data to the length units MagPick divides the data value by this value before stack profile plotting It converts data units mostly nT to length unist meters gt This requires a good understanding of how magpick handles profile data In many cases the data set number is just 1 25 Basic operation of MagPick 10 11 12 13 You may need to experiment with it to obtain the best plot Preferred d
286. ogram or load new picks without saving of the previous picks a warning appears and you are given opportunity to save the job In case you have duplicated picks in the file secondary copies are discarded during loading The pick file itself is an ASCH file with a simple structure Each pick is represented by one string Here is the format of the string 1 3 numbers X Y and the field for end of the pick where the maximum value of the field is 2 3 numbers X Y and the field for end of the pick where the minimum value of the field is 3 Local azimuth to minimum second point from maximum first point plus Field direction value see figure B 4 Horizontal distance between picks 5 Two numbers coordinate of the middle point of the pick 6 One number always 0 000 This was implemented for compatibility with some software In case you did a false pick you can remove it by choosing Edit Delete pick option The cursor is changed to remind you that you are removing the pick Move it to the centre of the pick and press left button If you are close enough the pick disappears To remove all picks use Edit Delete all picks You will be prompted to save picks in the file if you do not want them to be saved simply press Cancel 5 3 2 Pick export Magpick provides some tools to export picks into external formats such as X Y Z dat file Autocad DXF format Atlas BNA format and in a couple of internal magpick formats to be drawn on
287. oints on the map You perform it by setting markers on the map which in turn appear in the profile view or by settings markers on the profile view which automatically appear on the map There are two pre defined markers arrow up and down When you set the marker first time it shows it as arrow up when you do it second time it shows it as arrow down When you do it the third time the first arrow up goes away and a new arrow up appears in the new place and so on Try the following next e In the profile view window go to Edit Set marker The cursor changes its shape to go to some point on the curve and click left button Arrow up arrears on the curve note that the marker can be set only in at the location where you actually have X Y Z data Inspect the red line on the magnetic map You will find the arrow up there e In the map window go to Edit Set marker cursor changes its shape and it becomes Point its center to some place on the red line the profile you are seeing in the profile window Click the left button The sign arrow down appears on the map Go to the profile view and find the same mark there Repeat the above operations several times to become familiar with it Note that at some extreme points in the profile view you may not see some types of markers Zoom to part of the map window where markers are located See that they appear on all map views Note that in the map view you can set markers on an active profile
288. om After you release the mouse button a new window with the selected region appears on the screen It can be zoomed again It is important to understand that all windows created by zoom share the same array map of data Several arrays can be opened at the same time If you decide to close all windows initial window and zoom window of given array choose File Close All If you have closed parent window you will not be able to see the full map again The only way to get back is to load the file again To receive short information about data in the window choose Options Info menu Here you can see the geometrical locations of the corners of the grid and the number of columns and rows as well as the local minimum and maximum of the data In some cases you can choose use MagPick for profile processing only You must always load a grid to create the map view and see locations of profiles You may want to create a dummy grid which has following format DUMMY 100 100 62740 63200 33130 33820 9366 12 17963 5 1 Use the magic word gt DUMMY so program can recognize the file 2 Numbers of columns and rows of an empty grid 3 Minimum and maximum X coordinates 4 Minimum and maximum Y coordinates 5 Minimum and maximum of the dummy field It should be noted that in this case the program creates a real array i e allocates memory there fore you should not choose large numbers for rows and columns In case of a
289. on with pen up 1 with pen down You can use this file in MagPick directly just select it with line option 5 2 3 Using ArcInfo TM shape files in magpick If shape files are available they can be used in MagPick however a conversion is required There is a command line program shipped with MagPick called shp2mpick or shp2mpick exe under MS Windows This program converts linear features from shape files into a MagPick line file see above Both shx and shp files must be placed in the same folder Then program can be called as shp2mpick exe shp_file color thickness GEO UTM gt output_file here shp_file is the name of shape file extension shp color is color name might be RED BLACK see a 1 for full list thickness is line width GEO or UTM denotes coordinate system output_file is a MagPick line file Note that all lines in that file have the same color The core for this program was provided by Sol Katz skatz blm gov 5 3 Simple picking of magnetic anomalies 5 3 1 Simple pick Magpick provides two basic options to select specific points on the grid Note that these simple picks have important value they are used as initial positions for searching of magnetised spheres or lines inversion Picks can be saved into and loaded from a separate file Because the simple interpretation of magnetic filed assumes that the source is in between local minimum and maximum of the field the pick consists of
290. onality and dynamic shared or static library versions not from Info ZIP must be plainly marked as such and must not be misrepresented as being the original source or if binaries compiled from the original source Such altered versions also must not be misrepresented as being Info ZIP releases including but not limited to labeling of the altered versions with the names Info ZIP or any variation thereof including but not limited to different capitalizations Pocket UnZip WiZ or MacZip without the explicit permission of Info ZIP Such altered versions are further prohibited from misrepresentative use of the Zip Bugs or Info ZIP e mail addresses or the Info ZIP URL s such as to imply Info ZIP will provide support for the altered versions 4 Info ZIP retains the right to use the names Info ZIP Zip UnZip UnZipSFX WiZ Pocket UnZip Pocket Zip and MacZip for its own source and binary releases 1 4 SZIP Copyright and License Notice The SZIP Science Data Lossless Compression Program is Copyright C 2001 Science amp Technology Corporation UNM All rights released Copyright C 2003 2005 Lowell H Miles and Jack A Venbrux Licensed to ICs LLC for distribution by the University of Illinois National Center for Supercomputing Applications as a part of the HDF data storage and retrieval file format and software library products package All rights reserved Do
291. onent on the stack profile plots The stack profile feature itself can exclude the linear part from plotting However in some cases the geological part of the field behaves as a higher degree function The smoothing of the original values with following substraction of smoothed values from the original can stress local anomalies 49550 Original data Serres Smoothed 49540 49530 49520 E E ke 2 S 49510 b 4 3 E D oO 49500 4 49490 J 49480 4 49470 i i i i i 6800 6900 7000 7100 7200 7300 7400 X coordinate m Figure 32 Data smoothing with cubic spline To smooth profile data use the following 67 Profile data transformations e Create a profile view simple Profile view or All profiles in the window kind of view Then go to Edit Smooth Smooth profile data dialog appears on the screen Here you can enter the next values 1 What to smooth you can apply the operation to all profiles currently active profile s or 1f there are two valid marks on the active profile the part between them can be smoothed 2 Enter the smoothing parameter which controls the smoothing degree Smaller values pro vide more smoothing 3 Choose the color with which the smoothed curve is to be plotted e After you press Ok MagPick will proceed with the operation This process can take different time depending on how many profiles and points you use In the end profile the view gets up
292. only is needed if you work with GMT cartographic system Position file Besides appending results of estimation to the worksheet the program saves the position in the file which has a format compatible with the pick file 1 e 1t can be loaded into MagPick as a new pick file This feature is obsolete The file is overwritten after each inver sion To keep the original file change name by means of the Change button 130 Estimation of magnetic sources N e Calculated grid Synthetic field after calculation should be loaded into a new map view to compare with observed field You can change file name by means of Change button Difference The residual grid is equal to the observed minus the calculated It is worth to make new map view and load it to see how it looks like You can change file name by means of Change button e Start iterations This button starts the inversion procedure Remember that if you choose the wrong parameters for instance you started the inversion for all your map and all potential sources the calculation can be endless Then you will have to stop it During inversion the program prints results of each iteration on the screen Unix systems only Here is an example of such output 11 Discrep 52 47 Lin 4 97e 03 Non lin 2 42e 01 lev 49729 32 l 2 4 5 N 11 Current iteration number Discrep 52 47 Current discrepancy for given iteration nT This number has to be reduced dur ing
293. ortant They are the current depth and discrepancy The last one should decrease Wait till it finishes For pipe inversion you normally do not have to press Cancel As soon as it is done a new dotted lines appear in profile inversion window This is the graph of calculated field You can compare it with observed one If the fit is good you can keep this result If not it is better to remove result of alst estimation and try again for example with different initial depth 6 Results of inversion For dipoles you can see results of inversion in the worksheet There is another different from dipoles worksheet for pipes Go to Inverse Worksheet Pipes window with results appears on the screen 6 on figure 165 Once opened it can not be closed The pipe worksheet supports the same set of operations as the dipole worksheet loading saving from file deletion of the raw undo deletion export as DXF or BLN format The results of inversion is also shown on the map view as where 5 denotes estimation number the same as row number in worksheet It is shown on figure as 7 When you remove the row from the worksheet it is automatically removed from the map view too 7 Estimating stability I strongly encourage you to try different estimations with a different initial location depth This way you can get an idea how real your estimation is If the program ends up with the approximately the same numbers this means everything is Ok If not
294. ou can select all or none of the profiles crossing the parent map window and you can select subsets in these profiles Only graphs plotted on the profile inversion view window are used for inversion A good practice is to change profile decimation before the inversion if there was any decimation during initial load Each point should be loaded This task can be accomplished by the Resolution button The profile view window allows same basic operation with a mouse All these facilities are avail able under menu Edit e Set marker Put a mark on the given line Move the mouse to the place and click left button A mark appears on the screen for the type of mark see figure 18 Markers can be set on curves only and only at the data node The program chooses the nearest node and places the mark If decimation is large the actual mark position and the mouse position can differ considerably e Zoom You can zoom part of the window in the same way as for map views but the zoomed part replaces the content of the view This can be done several times If you work in Shrink to canvas mode then you can return to the state before zooming just by calling Settings and pressing Ok or use Redraw In case you are in the scale mode it is more tricky You should set scale factors back as they were before zooming e Remove This item is present only in the profile inversion view In case you have too many profiles on your screen you may deactivate them int
295. ound by the program based on end points of the line In latter case Preferred direction is important it allows proper handling of lines doing in opposite directions example lines going North South and South North if preferred direction is 0 then positive anomalies on adjacent lines are plotted in opposite directions preferred direction should be 0 or 907 Both Fixed direction and End points do not depend on quality of GPS track Fixed direction azimuth Value which defines fixed direction Fill type At your request part of the plot can be filled with a color Here you can specify part of the anomaly to fill positive negative or No fill It is also possible to plot only filled parts of the field select Positive no line or Negative no line Fill color Invokes the color chooser dialog box which allows you to define the fill color Clip stack plot In some cases big spikes for example the plot can be contaminated with data you do not want to see To avoid this you can clip the stack plot All values out of range will be plotted parallel to the track line Min Max Enter clip values here for the plot if you would like it to be clipped Middle line approximation To prepare a stack plot the program first must estimate which values are plotted on the right part of the path and which are on the left Total Earth s magnetic field is always positive and therefore should be transformed to make it suitable for such a pres
296. pdating the MagPick maps and refreshing the image in GE The following sections explain the export elements in detail 22 2 1 MagPick Image Overlay This layer represents the bitmap content of the MagPick map window Its properties are illustrated below on figure 1 Enable Image Enables or disables this element for export No picture would appear in GE if image is disabled 2 Google Earth Draw Order This value is used by GE to overlay different images It also can be changed later on in GE itself 3 Google Earth color This button calls simple dialog to allow the color and transparency se lection Note that these settings also can be adjusted in GE itself It is not recommended to use any color except white because it may interfere with the colored magnetic field map 172 Export and printing Color selection x gt 255 Green 255 Jo gt 255 Blue 255 Jo gt 255 Transparency o jos gt 100 Ok Cancel Image properties x V Enable image Google Earth draw order lo Google Earth color Image file TIFF properties Geotiff parameters x Screen Projection type TIFF compression No projection plain TIFF Lzw Export as simple UTM Export as Transverse Mercator Local system only Length units Local with Xtalse Yfalse local only Meter y Create TFWY world file JV Use transparent color Overall transpa
297. porting documentation Further UCAR requests that the user credit UCAR Unidata in any publications that result from the use of this software or in any product that includes this software although this is not an obligation The names UCAR and or Unidata however may not be used in any advertising or publicity to endorse or promote any products or commercial entity unless specific written permission is obtained from UCAR Unidata The user also understands that UCAR Unidata is not obligated to provide the user with any support consulting training or assistance of any kind with regard to the use operation and performance of this software nor to provide the user with any updates revisions new versions or bug fixes THIS SOFTWARE IS PROVIDED BY UCAR UNIDATA AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL UCAR UNIDATA BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE ACCESS USE OR PERFORMANCE OF THIS SOFTWARE Copyrights 1 7 ZLIB Copyright notice C 1995 2013 Jean loup Gailly and Mark Adler This software is provided as is without any express or implied warranty In no event will the authors be h
298. r can give up text or use a Lisp utility to convert text into polylines inside AutoCAD To do so XSHP LSP lisp program can be used available for free You can download it for example from http www acad co uk freesoft fonts htm Note that program requires ASCII font file TXT SHP in the same folder as the binary font file TXT SHX If you don t have an ASCII file you can use the utility SHX2SHP which is available from the same place to produce one Follow standard AutoCAD instructions to load the Lisp program Then select all text in the draw ing and call XSHP It might be slow but program will finally convert all you text into polylines it may not convert text inside Acad blocks Save result as DXF file Now start DXF2X YZ and pick your DXF file Use next settings inside DXF2X YZ e Ignore Z 2D should be checked e Entity headers should be checked Then press button Specify and check PEN NUMBER under Components All other boxes ENTITY NAME LAYER NAME LINETYPE NAME should not be checked e Under Data Formatting select Move to 0 Draw to 1 Now you can produce the XYZ file by pressing Save or Save as Here is an example of output 70 0 95 39 125 00 1 96 06 130 00 1 95 00 131 00 34 Basic operation of MagPick 1 90 00 134 35 70 0 104 71 125 00 1 105 00 125 99 Here 70 denotes the AutoCAD pen number and strings that follow are line segments 0 means moving in the positi
299. r pick Delete pick aia Zoom Delete eo Direction Pick profile Set marker NA Find marker i e A ee New Add color scale Add annotation Add polygon Add polyline Add map scale _ Add stack scale Add north arrow Add all frame annotations 7227 Edit All Figure 91 Use context menu to create polygon Note this dotted line this is modeled field It should follow solid red line observed field very closely as it is shown above The less the difference between these two the more reliable is the inversion result If these two curves do not match each other user needs to discard r the result and try again with different initial depth other part of the data etc In some cases it is not possible to obtain close match and therefore is not possible to carry out dipole inversion For instance picture 96 shows result of not so successful match Note that there is considerable difference between dotted and solid lines In a terms of RMS difference first good case delivered 4 3 nT the second bad case 10 nT In terms of dimensionless discrepancy good case gives 86 bad case 70 the close discrepancy to 100 m the better It is generally recommended not to use results with discrepancy less than 80 Now inspect lines 4 and 7 Note that fit between model and observed field is not so good here but we still could accept it The recorded anomaly shape on line 7 also is not exactly dipole Now let s
300. rapping was added to the program This provides a color wrap around certain range for example if range 0 500 then the data point 501 is colored the same as 1 etc It visualizes the map in the greater detail Shaded relief mapping was implemented with a user selectable position of light source Illuminated map presentation was added the color map shaded in accordance with the light position Map drawing speed was increased Easy profile loading does not require hand preparation of profile list file is now available One data file now can hold more then one survey line Program splits file into the lines during loading Stack plot was added on top of magnetic map Progress indicators were added to most time consuming operations such as data loading color equalization map and profile drawing Configuration file was re written to be more user readable than it was before The set of tutorials in this manual has been added Documentation has been improved Numerous bug fixes After all these changes were assigned version number 2 0 2 3 Version 2 x 2000 2004 MagPick development was driven by customer requests and Geometrics needs in the processing software The following features have been added Ability to export maps into DXF format assigning different map elements to the different DXF layers Profile data editing spline smoothing cutting re positioning including lay back recalcula tions
301. raws picture automatically Please note that there is no Undo operation This means you should be careful and probably save the grid also before clipping The clipping result is displayed on figure 23 To blank the data magpick uses the value 1 70141e38 in MS Windows version and 1 e35 in the Unix version 6 5 Clipping grid file using profile information If profile information and grid is loaded it is possible to assign dummy values to the grid nodes which are not covered with profile information This can be useful when spline gridding method is used because it creates artificial field in areas not covered with the data Magpick implements two clipping methods triangulation based and around data points Note that new grid has to be saved upon completion If user is not satisfied with results previous grid can be quickly loaded using Operations Reload menu 55 Grid operations 6 5 1 Clipping the grid using triangulation This is pretty similar to the gridding with triangulation Program builds triangulation network and then blanks all points which do not belong to any of the triangles The result is concave polygon which encloses all the data points Note that polygon can cover considerable areas with no data and there are no gaps inside the polygon The example is shown on figure 24 7400 717300 77717200 717100 7717000 Figure 24 Clipping grid using triangulation Note that con
302. rency level o Jo 41 _ gt 100 Ok Cancel Figure 121 The basic properties dialog in on the left Two sub dialogs Google Earth color and Image file TIFF properties are called with their respective buttons 4 Image File TIFF properties This is the same dialog as for TIFF GEOTIFF export In fact the TIFF file in embedded in GE KMZ fild The most useful selection is the Transparent color button which allows the user to make one of the colors typically white fully or partially transparent Note that to keep annotation background the user may use a color slightly off white For the same reason a light gray color can be used for Lat Lon and coordinate grids as it provides better visibility in GE 5 Map Possible selections are Screen and Bare color map In Screen the program exports the full content of the map window including margins grids profile annotations etc This all is exported as a bitmap In the Bare Color Map case only the colored magnetic field map is exported with no margins and other map elements 22 2 2 Profile Locations This control exports profile locations assuming profile data is loaded If a profile stack plot is used it is also exported into a separate GE folder using the same colors as shown on the screen The properties dialog looks is shown on figure l The KMZ file is in fact just a ZIP archive with different files and the extension KMZ 173 Export and printing xi M Enable prof
303. required to report from the sea surface If neither altimeter nor depth sensor are available only depth from sensor can be computed 163 Pipeline data treatment c Model background Could be DC constant linear or square function d Initial XY seed Selection are automatic and picks In case of automatic poly line inter sections are used In case of picks user should put pick in the map e Initial pipeline depth Enter expected cable depth The reference could be from sea floor water surface or sensor depending on how to report depth above 3 Miscellaneous a Use sensor depth If this box is not checked program cannot compute depth below water level b Use altimeter Use O for altimeter if not checked c Total non linear approximation iterations Default is 2000 might not be reachable d Derivatives Use analytic or numeric derivatives for non linear optimization Analytic is supposed to be faster e Create protocols and protocol folder If this box is checked user should define a folder where all results of the approximation including observed and approximated fields are saved to be used for future plots or reports By default program only saves results of the approximation but not the fields Results are reported in the Dipoles worksheet The Object field is PIPE QAS for Analytic Signal approximations and PIPE TF for Total Field approximation After fitting is completed us
304. rify your coordinate calculation prior to use As of March 2011 this procedure is obsolete because new better approach is availabe using PROJ LIB software 26 2 Procedure outline It is pretty usual in the United States to present geographic positions in the State Plane coordinates There is no easy way to re compute Latitude and Longitude or UTM Fasting and Northing into State Plane coordinates however thanks to US Army Corps of Engineers these is free software available to carry out the transformation This software program is called Corpscon and is available from website or corpscon html This program runs under Microsoft Windows operating system unfortunately it apparently does not run under Linux even with wine Windows emulator Below is a general pro cedure of how Corpscon can be used together with MagPick to deliver results in the State Plane coordinates This discussion assumes that data is presented as set of profiles However if user has gridded data in short UTM projection the method below still can be used In this case the grid should be split into XYZ data with Lat Lon coordinates first data can be re projected in Corpscon loaded back into MagPick as profile data and re gridded 26 3 Preparing data for Corpscon We assume original data is in Lat Lon and is loaded into MagPick using short UTM transformation We could process profile data do profile filtering leveling background removal etc entirely in MagPi
305. rizontal separation e For Analytic Signal enter the physical vertical separation from the plane of the two sensors for the third sensor Save into the file File name for analytic signal data A file with one data channel will be created Use the button to navigate the file system 6 Load data upon completion This checked box will command MagPick to discard any pre viously loaded total field data and load the newly created profile analytic signal data upon completion The computation generates a single channel track and a single channel data file 7 Remove median prior to operation This should be checked most of the time It addresses the fact that cesium magnetometers are not absolute instruments and therefore could have a constant DC offset of 1 2 nT between any two of them MagPick computes the difference between the two channels along each profile line computes median of that difference and removes it before computing Quasi Analytic signal 98 Quasi Analytic Signal Gradient parameters xj Transverse sensor separation m JIES Magnetic sensor 1 channel Magnetic sensor 2 channel 2 Wertical middle channel B Gradient type Quasi Analytic signal Vertical separation m f 5 Save into the file aii_ MSFisurvey_2009yuly_29_as dat a M Load data upon completition Y Remove medain prior to operation Warning Loading data upon completition unloads currently loaded profi
306. rofiles Smooth XY A dialog identical to data smooth dialog appears on the screen e Choose what you want to smooth It can be or All profiles or Active profile or Between marks The latter is available if both marks are set on active profile e Specify a smoothing parameter Remember that the smaller values provide more smoothing Value 107 is good to start with Smoothing may fail if this parameter is too small less then 10710 e Then chose a color to plot the smoothed positions This allows you to preview result of smooth ing and compare it with original positions Note that a stack is not plotted if you have a smooth preview it may obscure all the picture After you press the Ok button the program redraws the current map view any other map views you have to redraw by hand You have now chance to compare the smoothing result with original track If you want to repeat it just do it again Previous results will be automatically discarded To accept changes go to Profiles Accept All original profile data is replaced with transformed data of course only for profiles where you did transformations You must save the profile data or the result will be lost after you exit MagPick To discard the transformation results go to Profiles Discard The grid view will be redrawn and the transformed part disappears 7 3 3 Shift dragging along profile Typical marine magnetometer systems consist of a GPS receiver mounted on the ship and a
307. rovides schene for presenting profile data Some additional data like road a map costline can be loaded on top of the grid data too Loading of grid data is not complex All you need is file in the format which can be read by MagPick Loading of the profile data is more compilcated You should a prepare profile description file to begin with Alternatively MagPick can prepare this file for you but you ll have less control You do not have to load the map data to be able to load the profile data As soon as the profile data is loaded it can be interpolated to create a grid file loadable into MagPick You can set marks picks everywhere on magnetic map These picks might represent places you consider to be interesting Picks can be saved into file and loaded again You can delete a pick you don t like Picks can be exported into some formats readable by SURFER and AutoCAD The name of the program MagPick was given because of this feature You can estimate the location of magnetic sources To do this some approximations should be used Presently MagPick allows two kinds of sources Magnetic dipole which is good for a local magnetic source s and magnetic line which fits objects like pipes You can find a geometrical location and an amplitude of the source and in some cases its mass Results of estimations are viewed as worksheets and can be saved orloaded from files as well as exported Under Uxnix start magpick with command l
308. rsion 2 8 Current versions of MagPick allow loading an additional channel from the same data file by first selecting string in the profile list and then pressing the Add channel button top part of Figure 14 This will skip file selection dialog and go directly to the Create profile description dialog bottom part of Figure 14 Repeat the same operation as for the first channel Note also that the same file can be loaded multiple times using different columns After you have selected all data files you wish to load you can check the Save as profile list box and press OK to start loading process You will be prompted to save result of your work as profile list file This means that when you need to load this profile information the next time you just pick list file directly menu File Profiles Load list without going through all these steps again After processing of all the profiles the program reports how many profile lines you have If some profile data has been loaded already it asks would you like to erase this data from the memory or just append new data to the previously loaded set You may be requested to close some profile views if they are open on the screen If after profile loading go to File New you have a choice make profile or map view In the case of map view MagPick will create a dummy grid to display positions of your profiles If you only need the stack plot then you don t need to perform any other actions To prepare
309. rt the content into GE as set of interactive data icons This export is controlled by the following dialog see figure 123 1 Enable Dipole Export Enables or disables this element for export No dipole locations would appear in GE if this feature is disabled If there is no dipole worksheet available the feature is automatically disabled and a warning is posted 2 Position annotation format Controls how the position is displayed in the GE balloon which appears when user clicks on the target The position can be displayed as decimals degrees and decimal minutes or degrees minutes and decimal seconds 3 Digits after dot This controls the representation of the decimal part on the position balloon 4 Report positions as Depending on this selection positions can be exported as Lat Lon full UTM or short UTM coordinates 174 Export and printing Dipole export xj V Enable dipole export Position annotation format Degrees minutes Digits after dot 6 Report position as Lat Lon C Full UTM Short UTM V Report dipole angle with Earth magnetic field M Report dipole inclination angle M Report dipole declination angle Report dipole magnetic moment cgs Ok Cancel Figure 123 Exporting dipole locations to Google Earth 5 Report These check boxes control which part of the dipole information is to include in the GE balloon The GE map on figure shows the dipole information in the case
310. s It is also more difficult for interpreter to deal with Here is some other improvements which were done that time Magpick now can interpolate data from profiles to rectangular grid therefore there is no need for additional interpolation program Currently two methods are available gridding with ten sion borrowed from GMT software and triangulation with interpolation see and 4 e For pipe and dipole profile based estimation data can be constrained by polygon drawn by user This presently does not work for dipole fitting based on map data e Some improvements were done for map presentation and the number of available map views were significantly increased including A fast but not accurate contour drawing algorithm was brought into MagPick Set of uniform palettes is directly available and viewable with MagPick A new kind of color scheme gradient palette was implemented This control allows easy manipulation of the color scale saving and loading from file and much more Color equalization method allows visualization of maps with maximum color contrast Currently the feature is available with a uniform palette This allows a color map to be produced where each color occupies an equal space greatly increasing map resolution Visit http imina soest hawaii edu gmt No information was found forbidding usage of GMT code 12 History and features of Magpick A new kind of coloring color w
311. s You should have enough mem ory to spool it For the task you just did helens2 grd with contours it used 11 8 MB Questions e How to make magpick do not plot any color map 27 2 Load profile information into MagPick Goal Show how the profile data file with space or tab separated columns can be loaded into Mag Pick You will be able to inspect the data as linear graphs elongated along local X Y or profile direction itself After this lesson you should be able to use MagPick as a simple viewer for profile Files We need files y 858m dat and g 858g dat which were generously provided by Paul Kot These are result of an export from Magmap Geometrics program and represent magnetic data ac quired with G 858 hand held magnetometer Two different techniques were used for positioning ground marks file g 858m dat and differential GPS receiver g 858g dat Therefore positions in first file are in some local coordinate system but in second file they are in California grid 1 Loading one profile data from one file Start MagPick go to File Profiles Simple Load Press button Add and choose file g 858m dat This file has a header string with names of the columns therefore you can see 218 Tutorial the number of the column and its name if the file does not have this header only the column numbers show up We need to decide which columns represent X Y and magnetic field File has 9 columns These are X Y TOP_RDG mag
312. s 3 8 those data from the original file will not transfer and therefore the dat file WILL NOT WORK in MagPick Click Convert to carry out the operation If program prompts on existing file replace it with the new content Figure 158 shows how the output window looks like after conversion Use this window to double check conversion parameters You may also use it to select false Northing and easting you need in MagPick In the example above appropriate false Easting would be 2200000 feet false Easting 98000 feet You may want to write these numbers down because they could be helpful while loading data into MagPick The beginning of the file after Corpscon may look like Longitude Latitude Z ALT T LINE DATE TIME 2201264 781 98067 315 1 00000000 7 34999990 47624 60546875 1 08 07 08 16 58 59 000 2201269 547 98073 160 1 00000000 41 99000168 47624 67968750 1 08 07 08 16 59 00 000 Here the two first columns were replaced with State Plane coordinates in feet User may want to use text editor such as notepad under Windows see http notepad plus sourceforge net uk site htm to modify header for something like that shown below Easting Northing Z ALT T LINE DATE TIME 2201264 781 98067 315 1 00000000 7 34999990 47624 60546875 1 08 07 08 16 58 59 000 2201269 547 98073 160 1 00000000 41 99000168 47624 67968750 1 08 07 08 16 59 00 000 Changing the header names for coordinate columns is desirable but not necessary Now data can be
313. s These have additional numbering based on linked map views 4 TBL targets worksheet data 18 Basic operation of MagPick 4 2 INE program settings files For each map view one INI file is saved plus one global file This file also saves UTM projection information ANNOTATIONS file with MagPick annotations for Map and Profile widows PICK files These are MagPick picks Drawing files These can have any extension excluding SER and are copied into user folder MagPick project files environment variable This section describes possible problem reported on 09 10 2013 related to saving MagPick project files under Windows 7 and possibly some other Windows operating systems Please let MagPick developers about this problem by e mailing to mikhail_tchernychev yahoo com By default MagPick uses system designed folder to create temporary folder which is needed while saving or restoring projects After operation is complete this folder is removed It appeared however that on some Windows systems MagPick cannot use this default temporary files location The possible reasons are security or and anti virus programs The problem manifests itself with one of the messages similar to presented on figure I message indicates serious error related to the file system You gt cannot save your project and this time Please go toHelp PDF menu and see section 4 2 on possible workaround Q Cannot set temporary folder to save or load
314. s com 1 5 Copyright by The HDF Group and The Board of Trustees of the Univer sity of Illinois All rights reserved The files and subdirectories in this directory are part of HDF5 The full HDFS copyright notice including terms governing use modification and redistribution is contained in the files COPYING and Copyright html COPYING can be found at the root of the source code distribution tree Copy right html can be found at the root level of an installed copy of the electronic HDF5 document set and is linked from the top level documents page It can also be found at http www hdfgroup org HDF5 doc Copyright html If you do not have access to either file you may request a copy from help hdfgroup org 1 6 The NetCDF Copyright Copyright 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 University Corporation for Atmospheric Research Unidata Portions of this software were developed by the Unidata Program at the University Corporation for Atmospheric Research Access and use of this software shall impose the following obligations and understandings on the user The user is granted the right without any fee or cost to use copy modify alter enhance and distribute this software and any derivative works thereof and its supporting documentation for any purpose whatsoever provided that this entire notice appears in all copies of the software derivative works and sup
315. s it was described above 2 Gradient This was select current gradient palette 3 Gradient from equalized or Gradient from uniform Second choice is presented if map is currently painted with uniform palette but without equalization Select Uniform 1 and then choose appropriate color scheme on the following dialog Check Equalize colors button Proceed as usual to the end of the Settings dialog and see the map Now call Settings dialog again and go the same way to the Palette type dialog however select choice 3 Gradient from equalized This will approximate color equalized palette with limited number of the gradient nodes This can be set by Number of color points slider at the bottom of the dialog Typically even a small number of nodes 10 20 provide good color approximation With choice 3 selected MagPick creates gradient color palette after you press Ok button using current data limits see B This new gradient color replaces existing one Needless to say that it can be treated as any color gradient palette However there is a difference typically it should be displayed with Equal sized mode In this mode color nodes are separated uniformly along the palette regardless of data values Opposite to that in the scaled mode nodes are distributed linearly in accordance with their data values Now proceed to the map redrawing Color map should not change much after this step To export color scheme into CPT or CLR file you need
316. s more than Distance value typically in meters If you choose any file columns than it will be used as a line indicator If the string in that column changes a new line is started Enter the Distance value if you are splitting data by distance otherwise this value is not important Enter Decimation This would allow to load just only part of the data For example if decima tion is equal 2 only each second point gets loaded Note that you can still get all points later within MagPick use Increase the resolution function in the profile browser Show which columns hold X Y or Longitude and Latitude positions and field If file has a header its fields are displayed If not just only the column numbers For marine magnetometers device depth below sea level and altitude above the sea floor can be loaded as well Use Depth and Alt controls to select appropriate columns of the file Use Don t use selection if these data is not available If data file has recored time and MagLog files always have it can be loaded as well just check Use time box and select appropriate columns Select also time notation American or European Pick colors for active and inactive state of profile Typical choices are RED for active and BLUE for inactive profiles Important If positions where recorded in Latitude and Longitude it is recommended to project them into short UTM form Otherwise some Magpick functions may not work at all or will get erron
317. s of such an interpretations are still to be inspected The procedure is available under Inversion Run batch Its parameters are identical to the previous one described in the inversion but instead of treating all data in the window MagPick does the following e Goes pick by pick For each pick it selects only the data around it 134 Implementation of inversion e Applies inversion for this pick Inspects a misfit If it is more than user specified value result is rejected if less than user specified value result is appended into worksheet e Repeats these steps for every pick As you see this method does not allow you to estimate a few magnetic sources simultaneously 17 Implementation of the inversion in magpick To find magnetic sources MagPick uses a simple form of inversion based on a model represented by set of dipoles Mathematical expressions for the field produced by such a source are well known and have a simple form This allows one to construct an effective inversion algorithm Here is the outline of some basic features of forward and inverse problems as they have been implemented inside MagPick It is important to understand that MagPick does not take into account demagnetisation effects which can have significant value in case of iron objects 17 1 Solution of forward problem It is known that a magnetic field can be expressed as a combination of second derivatives of the gravity potential Which in the case of uniform
318. s or you can set the total number of isolines In latter case levels are chosen automatically in accordance with minimum and maximum data values in the window and the Total number of lines contours Thus if Automatic is checked then you do not have to think about range of your data Contours can have odd level values If you choose Automatic then all controls labeled with a on figure 4 do not affect the plot appearnce Total If you go with Automatic you can choose the total number of contours used to plot a picture Min Max Minimum and maximum values for contour lines 23 Basic operation of MagPick 10 11 12 1 Method of choosing intervals If fixed contour values are taken from list 2 Total number ai contours if Automatic if automatic data interval divided per E is checked if Fixed values has no effect Total to obtain contour values FF x 6 List of contour values gt Fixed values y Automatic Total 25 e Gets updated when Contours E E1000 J3 ou press Calculate ie ES contour values you pi i 2100 00 5 N Can be read from file 99 00 Max 100 00 _ 98 00 4 E nter here contour interval 1 00 7 Read contour values 37 00 Interval J 1 00 C 96 00 from file only 1 st column gets read 1 8 Allow you to set color Read from file for contours one for M color na all of them 95 00 Cal
319. s the minimum and maximum values for the field at the pick s ends You can use these values to classify your points MagPick also offers automatic picking See main manual for this option You should inspect results of automatic picking before accepting them 6 Pick export MagPick allows converting picks into its internal drawing format for usage as a base map Pick can be also saved in SURFER dat format or exported in a very primitive form of AutoCAD DXF file No guarantee your software will read it If it will you might have to scale the picks to fit them on existing maps 227 Tutorial 27 5 Finding magnetic dipoles Preface Many local magnetic bodies can be approximated with a simple model uniformly magne tized sphere magnetic dipole This simple source has only six parameters to be estimated by the interpreter these are X Y Z location of the center and Jy J and J components of magnetization vector MagPick does not consider the dipole as one which has only induced magnetization in this case J would be parallel to the direction of the Earth s magnetic field It includes remanent mag netization into consideration and therefore total magnetization is represented by an arbitrary vector J Modern magnetometers measure total field which is the projection of an object s own magnetic field into direction of the Earth s field Therefore for proper parameter estimation we should know direction and value of the Earth
320. s were sources might be located When such a place is selected by map view or by means marker facilities on the profile view the interpreter does zoom in surroundings and creates new map window This last window is used as a parent for profile inversion window After the profile inversion is opened the interpreter can view all profiles crossed and select a subset of them Very often the interpreter has to change decimation of data to get all available points into the inversion All these options can be reached in Browser dialog box The next most important step is choosing the initial positions of the sources It is done exactly the same way as in the case of grid based inversion by means of picks on the map Note that it is possible you do not have a real grid and must use a dummy grid implicitly created by MagPick or loaded from dummy grid file It might be very useful to uncheck Snap to grid to allow picks to be located anywhere After the profile selection is made the estimation procedure can be started Choose Inverse Run Dialog box similar to the one in the case of grid inversion appears on the screen Here is the difference e Smooth Z parameter Checkbox and value In case you have noisy Z values it is possible to apply a simple method of spline smoothing If you need it check it on The normal value for a smoothing parameter is 1 e 5 less parameters give more smoothed curves Normally changes of orders required
321. s you to set general title as well as X Y annotations It also controls font size of the plot excluding annotations 22 5 1 How to prepare plot to pre defined scale Most common task is prepare plot to scale say 100 meters in one centimeter on paper The recom mended procedure can be described as the following First of all disable all time consuming plots such as color map profiles and profile stacks in the map view You may need a few iterations to come up with satisfactory paper layout so those additional plot elements would slow each iteration considerably Leave only coordinate grids and annotations Re enable other plot elements for the final hardcopy Now set up the scale Make sure Fit paper size is not checked In this example we assume scale 100 m in one centimeter on paper It means that 100 00 cm of real topography fit to 1 paper cm delivering a scale of 1 10000 so set Scale map units in one paper unit to 10000 Set X and Y offset as desired You may have to adjust them if plot does not fit on paper Use Preview output Press OK GSView shows you the result 182 Export and printing e Use GSView controls to adjust paper size AO Al etc e Repeat operation changing X Y offset and font scales till you are satisfied with the result Enable then all other plot elements and make a final plot e Using GSView File Convert menu you can convert resulting PS file into PDF Please type file extension explicitly
322. s39 666EZZ LZ 6S8S d UOISJOAU JO S INSOY Z V Mo sef basy z zA zx w ix 1 p3 ag O1d ds EN g N Jaysew 385 E ZLASE Lb bS WL pe Se o 0L 0Z QEz Ate 0S 09 Oti J panop prey pareimojeo A pios Prey peniesqo NAO ba Z 2 uy umoys elep ajyoid jojd 0 uonoaq MOPUIM UOISISAUI 4Old S9 IJOJO MDPIS YM 1 yum pajerossy z pub Awuunp jojd dew 10 09 ou Mala de 00z3 0013 0009 OJSG suondo asianuT pa ad asi8Au saagaweseg Yp3 a Finding pipe location with MagPick Figure 165 236 Tutorial 5 Profile based inversion Now we are almost done In the profile inversion window go to Inverse Run Here you should enter Earth s field parameters Total Intensity 35178 03 nT Inclination 37 80 deg Declination 351 84 deg Other important parameters are Azimuth of X axis 90 Number of iterations 4000 big enough Limit to stop 0 Initial depth is very important parameter Set as 5 for instance Change files as you need but this is not important now Set Object type as Pipe and press Object specific Here set Number of pipe segments as 1 and check Use infinite approximation This corresponds to the case b from figure 164 Press Ok and press Start iterations Now the program is calculating Watch the progress indicator 8 The last two numbers arethe most imp
323. se leveling can introduce its own linear gradient and DC offset those are removed by fitting linear spatial model 4 Linear trend from step 1 is added back to the data to keep general geological trend of the area The procedure above certainly has its own drawbacks For instance if all main profiles profiles where made at one time and all tie lines made another day there could be DC offset between these two sets of profiles which affects linear background estimation Further more there could be prob lems if user needs to stitch patches which were individually leveled 9 2 Leveling operation In this section the data sample courtesy to Jack Melton http jwmelton com is used Data is available under tutor leveling User can load file leveling example dat using Simple Load 89 Leveling tie lines function or directly the file leveling example lst with Load list menu Data can be gridded as usual However gridding is not needed for profile leveling it is only used here to demonstrate leveling results in the concise matter Figure 55 shows gridding result for raw data using splines Gridding of unleveled profile data A 4240 4260 4280 4300 4320 4340 4360 2840 2840 2820 2820 4240 4260 4280 4300 4320 4340 4360 Magnetic Field nT 50104 50106 50108 50111 50116 50122 50138 Figure 55 Grid of unleveled profile data As it can be seen here there is strong misfit between lines going into different
324. sed and not required anymore Just clear what you need press OK and call Auto short UTM again 2 Assuming profile data is recorded in WGS84 just press Set default button to fill in from field It wills as proj latlong daatum WGS84 3 Fillis to field by typing projection parameters The simplest case if EPGS ESRI or other code is know For instance to California State Plane zone 2 NAD27 you could type init epsg 26742 or use EPSG button to select from list Note that codes listed at the top of the list are datums not projections Append other parameters separating them by space For instance EPSG 26742 is measured in feet to change it to meters add units m 4 When you are using projection for first time you have to check if it is computed as ex pected Use independently obtained test points Set false northing and easting to zero and use calculator buttons to compute projection The following software could be used to verify transformation Corpscon US State planes Geotrans and from Royal Dutch Navy as well as commercial packages Note that in case of 7 parameters transformation some of these packages require inverse sign for rotation angles 5 Press Set offsets from data to automatically fill in appropriate false Northing and Easting 6 Proceed with data load as usual 12 6 2 Typical parameters used with from and to statements All parameters have form lt name gt lt value gt and should be separated by space w
325. sible formats e SURFER ASCII This is an ASCII grid format from Golden Software It is compatible with SURFER and machine independent because it is ASCII e SURFER BINARY The same as above but binary It is NOT machine independent little en dian and big endian computers becomes incompatible if you use this format to exchange data It corresponds to SURFER binary grid format up to version 6 e NetCDF This is binary format based on NetCDF library It is machine independent and com patible with GMT system B All these formats can be read and written by MagPick Therefore if you are using only MagPick and only a certain type of computer it is not important which format you use Regarding space SURFER ASCII wastes maximum and NetCDF minimum After you have selected the format MagPick saves the grid file 6 3 Create clip path This function allows you to create a file which can be used as a clip to trim the picture on the screen No grid modification is involved and therefore no grid saving is necessary The sequence of operation is next e Go to Edit Polygon Mouse changes its shape to the pen Draw the polygon The left mouse button adds a node to the polygon the right button removes latest node To close polygon hit its first point To draw a new polygon go to Edit Polygon one more time existing polygon will be erased e Go to Operations Save clip Pick the file name you want Press OK e After the file has been saved
326. siderable areas with no data are not blanked This function is available from Operations Grid clipping Clip on triangulation menu 6 5 2 Clipping the grid using profile data points This clipping method is using profile data directly For each data points it considers circle around this point with user defined radius All grid points inside this circle are not blanked All data points outside are blanked Program checks data points one to one and builds clouds around the profiles This yields complex clip pattern with possible gaps inside the area Typical example is shown on figure 25 This function is available from Operations Grid clipping Clip on profiles User is asked to enter clip radius in meters Note that this operation can be time very consuming depending on amount of profile data 56 Grid operations Figure 25 Grid clipping using profile data points directly In this example clip radius of 5 m was used Note gaps between profile lines 6 6 Exporting grid data as XYZ file and mosaicking in MagPick This section describes how to convert grid data to XYZ profiles The feature can be useful when data ought to be exported into some other software as well as when already gridded data are to be combined into single map also called mosaicking 6 6 1 Export into XYZ This function is available under Files Export XYZ menu First file selection dialog called with two possible f
327. some cases below the level of measurements That is if there are no gravity or magnetic sources between these two levels This procedure is called upward continuation of po tential field It is generally a useful and physically meaningful filtering operation It allows you to smooth the field and eliminate small anomalies from the near surface objects Subtracting the upward continued field from the original field reduces the influence of the deep objects therefore reducing the regional trend stressing a magnetic response from shallow objects Theoretically the field also can be continued downwards untill the continuation level does not cross any field sources However it has been proved that this operation is unstable It greatly magnifies existing noise and makes the field unusable To cope with this problem relaxation regularization can be used This may help but only to certain extent Magpick uses very simple kind of Tikhnonov regularization In the spectral domain upward con tinuation can be written as s u v F u v s u v x fluv gt F u v ou x f u v here f u v is the spectrum of the field to be transformed F u v is the spectrum of transformed upward or downward continued field s u v is the spectrum of the transformation and Q the small regularization parameter You should try several values of amp to find a best for your case start with small vales like 107 The field in the current grid view can be upward
328. stance 7 Decimation While reading the program can take only part of the data each 10th sample for instance It increases the speed of loading and all subsequent operations In most cases decimated data still has enough resolution to represent geometrical position of profiles and field graphs If then one decided to load all points it is possible to accomplish it inside MagPick 8 Sequences of four numbers X Y Z T for each data set Thus the total number will be the number of data sets x 4 The Z axis goes down as normal in geophysics In case you do not 39 Basic operation of MagPick have Z in the file you can specify a constant value by typing expression h value instead of number of Z column Here value is desired Z 9 Next information is optional and reflects features of an off shore magnetometer array It allows you to calculate the GPS heights of the sensors if GPS hight of antenna and depth of the array are known To take advantage of this feature print A at the end of the string and then troughout the space column number in the data file where the GPS hight is and then the antenna hight above sea level in meters If MagPick finds an A it uses the following expression for Z coordinates for all datasets 1 N a heps antenna mF joa N Where N is number of sets This expression recalculates all elevations into the geodetic system Then MagPick changes sign to reflect downward direction of Z Here is an e
329. t MagPick will only use data inside the polygon s In this case wit would be parts of the lines 4 5 and 7 Other type of the constrains as as rectangular or circle is also available but we use polygon as simplest and most obvious 2 Initial depth of estimate This is the guess of how deep target could be Note that Z axis is pointing down therefore all depths must be positive In this particular case 20 m appeared way much the 2 5 m would be more appropriate but process still converges The reference for initial depth is the same as selected below under How to report target depth selection box 3 How to report target depth The choices are From sea floor From sea surface From sen sor The first choice only works if magnetometer is equipped with altimeter delivering rea sonable altitude data and depth sensor The second choice could be used if depth sensor is available Note however that you may need to correct depth sensor data for tide first The third choice always works but it is least informative In this example we use depth from the sea floor positive depth means that object is buried and negative depth would mean that it is above the sea floor The latter is possible due to non dipole nature of the source or noise in the position data After inversion is complete profile graph looks like 95 141 Single magnetometer inversion Edit Redraw Select Pan map Simple pick Rectangula
330. t could be good for the first try Use IGRF for Earth field Inversion procedure except Free dipole s see below require parameters of the ambient magnetic field such as declination and inclination Program can compute these parameters using known gepgraphycal location and IGRF field model Check here to enable this option Options listed below are for manual values 1 Main field Inclination deg Enter Earth s magnetic inclination angle between magnetic field and horizontal plane see figure 86 for reference 2 Main field Declination deg Enter Earth s magnetic declination angle between magnetic field horizontal component and direction to the geographical North see figure 86 for ref erence 3 X axis azimuth deg Local projected X axis azimuth Data type This option mostly experimental Use Profile default in cases of total field same as slection Total field Other selections are Vertical gradient and Finite vertical gradient Sensor separation m Sensor separation if finite vertical gradient option above is used Ex perimental Extended area Use this option to automatically include additional survey lines in the prox imity of the selected part of the profile Possible selections are 1 None 1 line Only data between markers from the current line are used No other data is included This is most widely used option which does not require additional input from the user 2 Rectangular Include all
331. t data set has to be split into lines NN could be an integer number with out or real number with In first case it is treated as column in the file which has line number Any character string can serve as a line number MagPick assumes that the new line starts when a string changes In the second case with the value is treated as a distance be tween adjusted points to break data into separate lines If the distance between points is more than the current value new than a line starts Note that this field is optional 2 It may or may not contain the words XFALSE NN1 and YFALSE NN2 Values NN1 and NN2 are false Northing and Easting values to be added to X Y coordinates in the file Note that they must be negative if you want to reduce for example full UTM coordinates to short ones This is a particular useful feature if the data is presented in full UTM format To decrease overhead MagPick uses floats 4 byte words to store all values Therefore loss of accuracy for full UTM coordinates is possible Use false Northing and Easting to avoid this loss Note that these field are also optional 3 Name of the profile file with a path if it is not in the current directory 4 Color name for plotting inactive profiles on top of magnetic map 5 Color name for active profiles 6 Number of data sets in the current file One file can contain more than one profile for a multi array magnetometer system for in
332. t means that if the user needs to prepare Excel file with positions formatted as latitude and longitude he first needs to adjust format and then export Program supports the following formats 1 Comma separated values Those are can be read directly by most spreadsheet applications such as Microsoft Excel or Open Office Calc Under Windows environment Magpick calls default spreadsheet application upon saving the file bringing new table on the screen 2 Geometrics MagLog FLAGS file Those can be used during data acquisition as user defined flags 3 Geometrics MagLog MAP file This is vector file to be used with MagLog program as a background 4 Atlas boundary BNA file to be used with SURFER from Golden Software 5 DXF format to be used with CAD systems 101 Simple magnetic anomaly positioning 11 2 Picking targets directly from profile lines 11 3 Profile manual targets MagPick includes function to mark point s on the profile view to be saved as a spreadsheet as possible survey targets Note that this method is very approximate and not a substitution for inversion Delivered results values can and will differ from the real ones but should be in the ballpark range from real most of the time To call this function user should limit area of interest by two markers and call Edit Pick profile target menu or use Ctrl Z keyboard short cut If function called from the menu target options dialog is displayed If keyboard shortc
333. t the part of the data as well as dashed line showing synthetic field Channels are marked with red star side right and blue port side left Extimated starget location is shown with the cross x Y meters X meters 7575 A Magnetic Field nT 7555 7560 7565 7570 7575 7580 7585 7590 7595 hie Figure 106 Second inversion for the same target Note that estimated position 2 is close to the first estimation and substantially off the red line This is typical for TVG inversion 154 HVDC cable inversion 20 Estimating location depth and electrical currents for HVDC cables 20 1 Brief theory overview High Voltage Direct Current HVDC technology is widely used to transmit electrical power over considerable distances using submarine cables MagPick supports inversion of Total Field Magnetic data collected over such objects which could be pair of conductors or single conductor both cur rying DC current MagPick treats these data as uniform i e there is no change in the data in the direction parallel to the current This implies that single total field magnetometer is sufficient to ac quire such data usage of transverse gradiometer is somewhat excessive even it allows verification of 2D structure of the field because both sensors should be recording almost identical values agnetic 5 Earth s magnetic field Earth s m A B Figure 107 Anomaly signatures which could be encou
334. t vector of the total magnetic field The analytic signal can be directly measured with the synchronized array of three or more sensors or it can be well estimated using the measurements from just two synchronized sensors deployed in the form of a transverse gradiometer In the latter case it is termed the Quasi Analytic Signal Figure 61 illustrates how the Quasi Analytic Signal is computed with the Transverse Gradiometer Only the component perpendicular to the direction of travel is measured directly The longitudinal component is obtained using data acquisition history along the path and may contain both temporal derivatives as well as gradient information The vertical gradient component can be estimated using well known potential properties of the total magnetic field Blakely 1995 by filtering in the frequency domain In MagPick quasi Analytic signal can be computed as the following 1 Compute Transverse component G of the gradient vector as a difference of two magnetometer channels divided by separation 2 Compute longitudinal component t G using the average of two sensors and data history along the profile 3 Estimate the vertical derivative G using potential field theory 2 D case Although this estimate is based on the assumption that the measured field does not vary in the direction perpendicular to the data profile the results are acceptable and useful True Analytic and Quasi Analytic signal are compared on figure 62 usi
335. t with shaded relief I assume that helens2 grd is loaded Go to Options Settings press Change palette and make sure thatUniform has been set Now click on Colored map check box You should click once or twice to invoke dialog box responsible for mapping Choose Shaded relief and set light azimuth 315 elevation 25 see as sun is rotating Set data scale as 5 This last value will be different for your real data and you have to try few numbers to find the best value You can see now a black and white steel picture with shadows Now go to the same place and set Color illuminated map Press Change palette and set Uniform 34 Press Ok See how long it takes now But you end up with a nice view Try the same with gradient land and sea palette as it was shown above Make your map nice add contours isolines The simplest way to do it is go to Options settings and invoke contours dialog box by clicking on isolines check box Here check Automatic Total 50 Fast drawing This means that your data interval will be divided into 50 contours Fast drawing means that no labels are available 217 Tutorial for the contours but drawing is somewhat faster I found this useful in some cases for a mag netic field If you have a lot of lines it can give a clearer picture than shaded relief or color map Press Ok See what happens Now for a slower way but with labels go to the contours menu as before check Fixed values type
336. take intersections with data lines as initial locations for approximations 2 Program will take into account angle between profile lines and the pipe line From the profile window go to Inverse Pipeline 1D The approximation dialog 12 is displayed The fields in this dialog are similar to HDVC inversion dialog However user should take into account that this is not an inversion but an approximation to find location and depth of the pipe line object All required parameters are separated in three groups 1 Data to fit 1D model 162 Pipeline data treatment xl Data to fit 1D model _ p Halfwith level depth rule Data Sa mi on Polyline name Line 1 How to report depth From the sensor Data type Analytic signal Model background Linear gt V Use data window m 30 Initial seed Automatic Channel for inversion f1 Initial pipe depth m fio Miscellaneous M Use sensor depth Iterations 2000 Derivatives Analytical Vv Use sensor altitude I Create protocols Inversion folder Ok Cancel Figure 112 Pipe line estimations dialog a Data Three different selections available i All profiles All data in all profiles are used Unless window option below is checked this selection implies that unnecessary parts of the survey lines were cut by the user and only useful pipe line anomaly remains Program will use all data The results will be sort
337. ter Space y Space y Close Figure 157 Converting MagPick output file into State Plane coordinates using Corpscon Make sure that Geo Coordinate Format at the bottom of the screen set to Decimal degrees in both right and left panes as well as Delimiter set to Space in both panes as well Using Input File Line you can count all your data fields in the file Now you need to tell Corpscon where coordinates are In the left pane set Latitude to 2 and Longitude to 1 In the right pane set Northing Y to 2 and Easting X to 1 This replaces Longitude and Latitude in the output file with 210 Coordinate transformation using Corpscon software State Plane Easting and Northing Note that you can just keep existing columns and append State Plane coordinates to the end of the string but in this case you need to use a text editor to modify the output file header which is copied by Corpscon from the input file The rest of the data fields can be mapped as in the table Name Field Point 0 Northing Y 2 Easting X 1 gt gt gt gt gt gt KIII gt gt gt gt gt gt lt lt lt lt c lt c lt Input Field 3 Input Field 4 Input Field 5 Input Field 6 Input Field 7 Input Field 8 CO NI N My AJU Table 3 Field assignment in the Corpscon software This will preserve order of the values in the output file Note that without including Input field
338. th above Possible selections are 1 From the sea floor This selection assumes altimeter and depth sensor both are available and altimeter does not have too many spikes It does not require depth to be corrected for the tide MagPick uses median depth in the selected area and reports target depth below it Note if target is located sideways depth on the profile is used which could be different from 152 Array inversion the depth in the target area This option does not take into account sea floor topography near the target 2 From the sea surface Depth sensor must be available but altimeter is not needed Depth is reported below the water level surface and user is responsible for converting in into depth below bottom using depth chart It is advised to use tide reduced depth readings otherwise result would be time dependent 3 From the sensor This is simplest option which does not require neither depth not altime ter 16 Create protocol DAT file in the inversion folder MagPick can record complete inversion protocol including observed and synthetic field along with all other parameters Check this box to enable this option Protiocal files one per inversion are created in the special folder and have unique names based on target ID and time when inversion was carried out These files are linked to the dipole worksheet 4 and are used to create inversion plots using File Plot inversion graphs from the worksheet menu 1
339. the main UTM setup dialog without closing UTM calculator Rotation To specify rotation press button Rotation To avoid confusion it is recommended to use false Northing and false Easting in main UTM dialog as zero To enable rotation check Enable UTM coordinates local rotation and enter coordinates X1 Y1 and X2 Y2 see figure 74 Project along axis specifies how line between X1 Y1 to X2 Y2 is located after rotation horizontally X or vertical Y It becomes new X or Y axis accordingly Use other projection advanced buttons invokes PROJ selection dialog discussed below If PROJ is enabled built in UTM is automatically disabled So 1f user enables PROJ all controls of the dialog figure 73 are disabled except Save Load Advanced For user convenience table of standard UTM zones is provided 110 Geographic projection transformations UTM and PROJ Local Rotation x ATTENTION Please read the manual before using this feature Project along axis X z Axis specification full UTM X1 1479312 000 Y4 15040650 000 X2 1517307 000 Y2 j4994857 000 Ok Cancel Figure 74 Rotation dialog box Zone C M Range Zone C M Range 1 177W 180W 174W 31 003E 000E 006E 2 171W 174W 168W 32 009E 006E 012E 3 165W 168W 162W 33 OISE 012E 018E 4 159W 162W 156W 34 021E 018E 024E 5 153W
340. thing Easting UTM zone and central meridian The central meridian value in UTM setup dialog is updated automatically Note that the UTM calculator is a modaless dialog box It means that you can do changes in the main UTM setup dialog without closing UTM calculator Besides the UTM calculator MagPick uses the UTM transformation in the next places this might be extended in the future e The status line coordinates of the mouse position inverse UTM is used This means you can see the position of the mouse cursor in Lat Lon To utilize this feature go to Options Status line Here you choose the format of the coordinates in the status line for example if your data already are Lat Lon you can use degrees minutes seconds and if data in UTM apply inverse projection Check Inverse UTM This means that every mouse location position is projected back to geodetic and formatted accordingly e Pick export For example when you need the final locations of your picks you can obtain them in the geodetic system applying inverse UTM during the export The UTM transformation setup can be called directly from the export dialog box e DXF export to AutoCAD You can apply the inverse UTM transformation during export to obtain drawing in geodetic coordinates It is recommeded you save the current projection parameters button Save in UTM setup dialog box and keep this file with the data Each time you are working with the data load this file again
341. this is when you are plotting a stack profile of magnetic data with the field plot per pendicular to the track If the GPS Global Positioning System has been used to acquire position information chances are that the path is not a smooth curve individual data points jump around If you use such a path to prepare magnetic field stack plot it will result in an erratic picture After a 72 Profile data transformations certain degree of smoothing the positions remain almost the same but path becomes much smoother and therefore can be used as a base line for a stack plot It should be noted here that MagPick actually constructs two splines X n and Y n where X and Y are positions and n is a fiducial number Each curv e X n and Y n gets smoothed individually The results are combined into X Y pairs which represent smoothed positions It would be better if the program were using time instead of the fiducial number n using of n implies that position data have fixed sample rate Usage of the fiducial number instead of time could result in unacceptable results when data has long position gaps Smoothed curve will spread the positions points over these gaps thus covering them almost equidistantly The rule of thumb is next Position smoothing works well when a time interval between data points is constant or almost constant To smooth position data follow the next steps e After profile data is loaded and map a grid view created go to P
342. thus avoiding large blank areas Typical example would be survey with azimuth of 45 perhaps elongated along pipe line route If only geographical projection is applied huge white areas would appear on the map consuming memory and slowing down the program The recipe in this case is the following 1 Select point new coordinate origin That point should be known in valid projected system such as UTM with zero false Northing and Easting This will transfer into 0 0 point in the rotated system As an example we could use UTM point from previous section such as 4096742 06 322037 81 125W 37N This is point X1 Y1 2 Select second point to define new rotated X axis orientation For the above example we could use point 4110884 20 336179 95 m which is 10000 m from first point and at 45 North East This is point X2 Y2 Note that both points are in projected coordinate system such as UTM 3 Opposite to the previous case false Northing and Fasting are set to zero It s a rotation itself which takes case of reduction of the coordinates to the short form Short UTM now refers to the rotated coordinate system right side of the figure 72 X increases when mouse pointer moves right Y increases when mouse moves up While converting from short UTM to longitude latitude the sequence is 1 rotate system back 2 apply inverse UTM or PROJ transformation 108 Geographic projection transformations UTM and PROJ
343. tion a colored map appears on the screen Check what was loaded Go to Options Info You can see all the geometrical parameters of the loaded grid 3 Change geometrical parameters of the view Let s play with it a little to learn how it works Our main tool will be Common parameters dialog available under Options Settings menu We proceed as folows call this dialog change something replot picture by pressing Ok Call Options Settings check Show x grid and Show y grid Set X and Y values as 2000 these are meters I believe Press Ok Now we have coordinate mesh Look at the status bar in the main window at the bottom You will see a string which starts with the word First and then 3 numbers These numbers are X Y and Z data values in the cell where the mouse cursor currently is When you move the mouse these numbers are changing You can check correctness of the coordinate mesh with a mouse this way You may note that these values are not exactly the same as mesh labels This is due to the finite size of one cell which occupies now exactly one pixel on the screen 215 Tutorial Now we would like to change this for example each pixel should occupy area of 3 x 3 pixels on the screen Therefore the picture will be increased 3 times Go to Options Size set X cell and Y cell sizes as 3 and answer Yes to the question which appears The picture is larger You can scroll it with scroll bars these are not alw
344. tion of the Earth s magnetic field This tutorial presents a numerical illustration of the procedure As an example a field from a rectangular object with only induced magnetization has been calculated see a on figure 166 Then this field was reduced to the magnetic pole plate b of the same figure As you can see the anomaly has now a perfect symmetric form Goal Illustrate how reduction to the pole works with perfect model conditions Files for that lesson we take file i70_d30 grd under on_pole subdirectory 1 Load data file Start magpick go to File Open and pick file i70_d30 grd Adjust size and color scale as needed 2 Make reduction Go to Operations Reduction to the pole Reduction dialog appears on the screen Here set next e Main field declination D 30 degrees e Main field inclination I 70 degrees e Declination of magnetization 30 degrees e Inclination of magnetization 70 degrees 238 Tutorial 3 Azimuth of local X axis 90 degrees e Check box Use reduction to the pole Note than all for values below this check box are filled in automatically Set elevation and regularization parameter to 0 Press button File with transformed field and pick folder and name for output file Let s name is on_pole grd If you want this name to appear in the history list check Add files to the history list Set format up with Format control e Press Ok button to start calculation Progress bar on the
345. to get back to the gradient palette editor see figure 10 and use context menu to export it Please save it as well for latter use with the same map The steps would be call Settings dialog again then Change palette select Palette type as Gradient Then right click between nodes or on the color bar to bring context menu select Export and SURFER CLR or GMT CPT options 4Equal sized mode is equivalent of psscale command with L option 31 Basic operation of MagPick 5 2 Drawing and clipping on top of the map 5 2 1 Magpick vector formats lines polygons points clip area Magpick allows you to plot some additional information above your magnetic field It can be useful to navigate inside the area Choose menu Edit Drawings dialog box appears which allows you to append drawing files Currently there are four types of information which can plotted 1 Lines You should prepare a file which has a special format Here is an example gt UTM GREY 0 0 0 10 10 gt UTM RED 0 1 10 10 20 0 Each line segment starts with the sign gt that makes file compatible with GMT system The word UTM indicates that the data is in meters GEO indicates that they are longitude and latitude In latter case MagPick will use the UTM projection before plotting the data Then you can choose the color of the line from a fixed number of names AQUAMARINE BLACK BLUE BLUE_VIOLET BROWN CADET_BLUE CORAL
346. tour color is black Press the Color to access the color dialog box and select another color All contours are drawn with same color Fast drawing If this is checked a fast but not accurate algorithm is used to draw isolines 2D version of marching cubes This does not allow labels but speed is much greater It is recommended recommend to check this box in all cases when labels are not required Label isolines If this control is checked the program will annotate contours Note that it works only when slow method of drawing is used Decimals This provides selection of the decimal point you wish for annotations For the mag netic field it is normally zero Distance between labels map units This controls how labels are drawn Program counts distance along each contour line when this value exceeds the limits it places a label You should specify this distance in your XY units 24 Basic operation of MagPick 13 Label length map units To place annotation text the program makes a gap in the contour line Text is scaled to fit into this gap This is were you set gap size and therefore inderectly the label size too You can plot profile lines with optional stack plot on top of the magnetic map Here is descrip tion of the dialog box which controls the profile plot parameters This gets called from Common plot parameters dialog box by clicking on the Show profiles check button see figure 5 is defined by ord
347. trols are the following 1 Use advanced projections If box is not checked all remaining controls except Cancel are disabled In this case user should use built in UTM Opposite 1f box is checked PROJ is used and all controls of built in UTM are disabled except Save Load functions Note that if there 1s an error in PROJ specification there would be no way out of the PROJ dialog except cancel 2 Field data projection or from Description of the input data projection with fields sepa rated by spaces In most of the cases it would be latitude longitude in WGS84 Therefore default value is proj latlong datum WGS84 Set default button clears the field and sets the default Note that this sentence specifies datum datum WGS84 which might not match datum of the existing data The absolute bare specification here for latitude longitude data is just proj latlong without reference to any specific geodetic datum 3 MagPick data projection or to This is projection used by MagPick to represent the data Use proj syntax to specify projection parameters see more on that subject in the next section Perhaps easiest way to specify projection is to key in EPSG coda In the example above it is init epsg 2801 where 2801 is the code for Louisiana South State Plane in meters Knowledge of the EPSG code allows quickly define projection without going into projection type parameters etc all that also can be specified using to string EPS
348. two points There are two ways of picking e Simple pick Go to Edit Simple pick for the window where you decide picking The mouse cursor will change its shape to Now move cursor to some point and click left button A ribbon dashed line appears after pointer Move mouse in the second point and click the left button again A black line segment with small crosses at the ends if need see figure 3 is drawn on the screen If the checkbox Snap to grid is checked on the ends of the pick are always in the centres of the grid cells It may not allow to set pick where you want if grid has low resolution In that case check it off Square picking when magpick helps you to find local extremum Go to Edit Rectangular pick the mouse cursor changes its shape to reflect your choice When square picking is used there are two things that must be done in the right order first show the area where maximum is then show where minimum is located Point the mouse in the corner press left button and drag The ribbon box will show your choice When the appropriate point is reached release mouse Do the same to the minimum point MagPick will search for the maximum point in the area you showed first Then it will find the minimum point in the area you showed second and draw a pick between these points 35 Basic operation of MagPick Picks can be saved into the file or loaded by File Open pick and File Save pick If you try to exit the pr
349. uires positions as geodetic latitude and longitude and MagPick typically handles data in short UTM projection inverse UTM transformation is required Check this box and verify UTM parameters by pressing UTM parameters button If data is loaded as Lat Lon with no transformation leave this check box blank 10 Value to compute IGRF can be used to compute a variety of fields such as Total Field Vertical and Horizontal Components or Eastern and Northern components Selection should match loaded data In most cases this will be Total Field 11 Preview Color After IGRF values are computed they are displayed on the profile view the same way as smoothed field Because vertical limits of the plot are based on loaded data limits IGRF values may not be visible initially User may need to adjust vertical limits by hand in this case After IGRF computation is complete results are shown on the profile plots This can be handled the same way as the result of smoothing or filtering For instance to replace all values by the differ ences between original value and IGRF go to menu Edit Accept and select All profiles Difference original smoothed values MagPick will subtract IGRF value from all the data 7 3 Profile position operations Magpick also allows set of simple position operations which can be useful to alter or correct profile positions These operations are available in map grid view under Profiles The operation dialog is shown on fig
350. und approximation up to 10 degree polynomial This function can be applied to profile or grid data and will remove a possible geological trend from the data or remove local anomalies from the data whichever is selected In both cases operation is available in Least Squares L2 approximation or Robust median L1 approximation However L1 estimation takes considerable time and therefore is not always practical 84 Removing polynomial background for profiles and grids even though it typically delivers better results Therefore the program defaults to L2 if user needs to use L1 he or she needs to overcome a set of warning dialog messages 8 1 Grid operation In this case the program uses cell X Y numbers as independent variables Option is available under Grid operations Background The dialog 49 is displayed Grid Spatial Filtering Model type Linear mi m2 x m3 y Estimation type Least squares L2 Retain results as Difference gridi madal gl Output format NetCDF Output file name C wx16BE samples magpick v 2 8 tutor reduced grd M Add file to the history list Ok Cancel Figure 49 Grid polynomial background dialog 1 Model type The following functions are available DC Linear Bi linear and 5 to 10 term polynomials The formulas are displayed in the drop list 2 Estimation type As it was noted above Least Squares L2 or Robust median L1 is avail able
351. ure If there is no profile information loaded all the menu items are disabled They become available after a profile is read from the disk All position transformation is first previewed by the user The transformed is path plotted on the same map with a different color If the user satisfied with the transformation he should replace the original positions with transformed position and save unfer different profile file name There is no undo after this point However profile data can be reloaded from the file and original positions re stored Use Profile view to do this If you do several transformations sequentially you should commit changes replace original with transformation result after each transformation For example you shifted the profile along X and Y then you smoothed the profile If there was no Accept command issued after the shift operation then the smoothing would be applied to the original positions not to the shifted 7 3 1 Simple shift This very simple function adds the shifts dX and dY parallel to the coordinate axis It is available under Profiles Shift XY After you call this menus item you should proceed as follows e Choose what you want to shift It can be or All profiles Active profile or Between marks The latter is available if both marks are set on active profile 71 Profile data transformations Profile XY positions drag x Apply transformation to Al profiles y Shifting method Drag profile y
352. ut Ctrl Z is used then dialog is only displayed for the first time Thus to adjust target selection parameters or change type of picking user should use menu and to proceed with bulk picks use keyboard Program figures out type of the anomaly see figure 68 and reports it in the table as the following e Negative monopole single minimum Program computes location of the minimum and re ports it as target location The half distance between markers is reported as approximate source depth The type name of the target is reported as M The illustration is 68 1 e Positive monopole single maximum The same as above but type of the anomaly is reported as M The illustration is 68 2 e Dipole minimum and maximum Program computes positions of the minimum and maxi mum and reports middle point as location of the source The half distance between minimum and maximum is reported as depth Type of the target is reported as D The illustration is 68 3 Program also can report depth readings at markers locations altimeter reading and date and time for each marker 1f these data were loaded as part of profile loading This way target can be easily attributed to the particular raw data if needed Profile targets are marked with letter P profile They are added to the same worksheet as targets acquired from the map There are three different types of manual target selection picking are available 1 Trivial Progra
353. ve inside polygon all inside polygon between marks save active 62 save all 62 set mark shift file short UTM show stack plot stack plot clipping stack plot direction stack plot fill color stack plot fill type stack plot labeling stack plot scale turn removal two kinds of views project file Projections 106 built in UTM example California State Plane 119 example from State Plane to WGS84 Lat Lon 120 example from UTM to State Plane example Gauss Kruger 7 parameters 119 example Louisiana State Plane 118 overview 107 proj command line parameters 115 Proj library 112 rotation 108 Quasi Analytic Signal Splitting profiles start MS windows 20 Unix SURFER format Target positioning grid profiles 102 tutorial 209 finding magnetic bodies 220 finding magnetic dipoles 222 finding pipe lines 227 reduction to the pole 232 view grids map 209 view map AND profile data 215 view profile data Universe Transverse Mercator UTM UTM central meridian 123 data preparation 122 pick export 123 Southern hemisphere 123 status line UTM calulator 123 version view many profiles 21 map map grid 46 one profile profile all view parameters fixed scale 47 mouse functions shrink to canvas profile inversion profile view worksheet 243 INDEX workspace file 16 wrap color scale wxWi
354. venience button which calls general UTM parameters dialog in case if user wants to check UTM projection parameters Export dummy values as If box is not checked dummy blanked areas of the grid are not exported This reduces number of exported data point and makes it more convenient for third party software to handle the data However if box is selected dummy values are exported as the number entered by the user on the right side of the dialog box It is important to take care to select a number that will be unique This number should not be duplicated in the data or locations After Ok button is pressed program proceeds with the export and new file is created 6 6 2 Creating and overview map from number of grids There is no mosaicking in MagPick However there is a work around using export XYZ option The sequence of previously prepared maps grid can be joined using the following procedure e Load grids one by one For each grid go to File Export XYZ and save the data as dat file Use inverse UTM to have coordinates as Lat Lon You can decimate data while exporting such as say exporting each other column or row Prepare as many data sets as you have grids Do not use Geoplot xyz format Do not export dummy values e Decide about projection for final map It might be that individual data sets had different UTM parameters most probably different false northing and false easting You may not use auto matic projection assignment for
355. viewed Color map This controls the appearance of the color map or disables the color map com pletely This control is marked as it means when you click on it to check an additional configuration dialog box appears In this dialog box you can choose several modes to draw a color map These are choices you have e No color map Simple does not draw it at all e Simple color map Each data value is mapped into a color without any tricks except autoscale and possibly wraping e Shaded relief This produces a picture as it would be if your data presents a surface shaded by a light source The light source parameters azimuth and elevation degrees can be set 22 Basic operation of MagPick 6 10 11 12 13 as well You also have to set the Data scale in many cases value 1 10 is ok but you might try different ones to find the best value You should use the Uniform palette for this kind of plot e Color illuminated map A simple color map can be combined with the effects of shaded relief It may look very impressive especially for topography data Change palette Calls the dialog box which allows you to choose the type of color mapping Uniform or Gradient Uniform is defined as a pre defined color scale spectra The data gets simply mapped into that color scale You can choose type of palette you like 0 41 and if Equalize colors is checked MagPick will apply non linear color mapping based on the data
356. w Attempt to load project file if some data is already loaded into the program by opening previously another project file or loading profile grids and other data independently results in the merge of these data sets A warning dialog is posted before merge can take place The merge rules are the following e New targets dipoles and pipes are added to the existing worksheets or new worksheets are created if there were none before Only one worksheet of any kind is allowed e Global profile data is added to the existing profiles e New grid views are created and data is loaded for each new grid window e New profile view is created for each profile window loaded For instance if the same project file is opened twice without being previously closed The number of targets in each worksheet is doubled e Number of loaded profile data is doubled e Number of map and profiles windows is doubled 17 MagPick project files 4 1 MagPick project file internals MagPick project file includes data files in native formats This way data can be used separately from the project by simply extracting files and loading them in the program Therefore content of the ZIP archive can be easily salvaged or used by other programs assuming ZIP signature is not damaged During project load MagPick extracts content of the archive into temporary folder and reads individual files into the program it reverses this procedure for saving operation In either c
357. ware program Ghostscript and GSView are available free of charge from http www cs wisc edu ghost When File Picture export Postscript menu is called dialog is displayed PostScript Export parameters J x Paper units fcm y Paper size Letter 8 1 2 x 11 in y Scale map units in one paper unit 1000 Orientation Portrait Landscape J Offsets paper units X f ie fi Output to C Printer File oP I Fit paper size X margin fi Y margin fi Printer command lipr Preview command C Program FilesiGhostgumigsvievigsview Titles Ok Cancel Figure 129 Postscript export dialog This dialog controls PS export It has the following controls 1 Paper units Centimeters or inches Depending on this field X Y offsets below are expressed in either units 2 Paper size Paper size for the plot Some most common formats are listed here However if user needs to prepare a plot in some specific format this field can be safely ignored This is only used when Fit paper size below is selected 3 Scale map units in one paper unit This option is used when metric scale is required It controls how many units on topography inches cm fit in one unit on paper 181 Export and printing 10 11 Orientation Paper orientation If Landscape is selected picture is rotated by 90 degrees counterclockwise Offsets Shifts in paper units from left bottom corner of
358. wing To edit each layers properties select them in the list box and push the button Properties The dialog box shown on figure L15 is displayed Here the user can alter the following elements e Enable or disable layer If the layer is disabled its definition and all entities are omitted in the DXF file If layer is enabled but there are no entities if user did not request to draw them in Common parameters dialog 3 then the layer is presented in DXF table but there are to entities If the layer is enabled and its entities are drawn in MagPick then they also are drawn in the DXF file e Layer name MagPick will assign names itself however the user can change them Do not enter same name for different layers 165 Export and printing Each string in this Oy FF CDKE export elements X list represent a separate layer Press Properties button to set each layer s parameters Typically magpick operates in short UTM coordinates However drawing can be presented in full UTM or Lat Lon Press this button to set false Northing and Easting or and inverse UTM Drawings to export Coordinate grid Contour map Profile lines Profile Stack Inversion results Picks R parameters A ON Polygon amp direction Press here to enter drawing title and X t Marks Drawings selected for output and Y axis titles Properties Transformation setup DXF Decimal jal Internal posit
359. wn simply because location of the target is not avail able and in fact ought to be estimated Looking at the picture one can note that target could be everywhere on the circle around survey line there could be infinite number of XOZ planes for instance defined by points 2 or 3 Location of the target in XOZ plane can be readily estimated even if the plane itself is not known It provides useful information such as target range from the survey line or possibly depth or offset from line and target location projected onto survey line The procedure can be used as a pattern recognition tool to find dipole anomalies on the survey lines automatically and classify anomalies as dipoles or monopoles MagPick uses that 2 D inversion as one of the options for simple pick feature It can be shown that Total Magnetic field in XOZ plane can be approximated as the following Tiotal J1 x xo z R Jo x x9 7 R gt J3z7 R gt ax bx Tic 138 Implementation of inversion where xo z is unknown position of the dipole in XOZ plane R y x xo z is the distance from observation point to the dipole ax bx Ty is the square term to approximate Earth s and geological fields in the area and J1 J2 J3 are linear coefficients which are functions of target magnetic properties directions of Earth s field and orientation of the XOZ plane The parameters to be estimated by non linear optimization are xo z The linear unk
360. xample of such a file data_23_09_97 mag_p02_23_09_97_filt dat BLUE RED 4 20 27 28 3 1 29 30 7 5 31 32 11 9 33 34 14 12 A 44 5 2 data_23_09_97 mag_p03_23_09_97_filt dat BLUE RED 4 20 27 28 3 1 29 30 7 5 31 32 11 9 33 34 14 12 A 44 5 2 data_23_09_97 mag_p04_23_09_97_filt dat BLUE RED 4 20 27 28 3 1 29 30 7 5 31 32 11 9 33 34 14 12 A 44 5 2 data_23_09_97 mag_p05_23_09_97_filt dat BLUE RED 4 20 27 28 3 1 29 30 7 5 31 32 11 9 33 34 14 12 A 44 5 2 While loading progress indicator appears on the screen You can stop loading if you want When it finishes the total number of loaded profiles is shown It is possible to have a slightly different format when you need to load several profiles from one data file Here the first column can have the following format number1_number2 Here number is the string number where profile data starts and number is the string number where data profile ends Here is an example of such a file 1_74 dat bl_east dat BLUE RED 1 1 2 h 0 3 75_151 dat bl_east dat BLUE RED 1 12 h 0 3 152 228 dat bl_east dat BLUE RED 1 1 2 h 0 3 229_304 dat bl_east dat BLUE RED 1 1 2 h 0 3 305_379 dat bl_east dat BLUE RED 1 1 2 h 0 3 380_454 dat bl_east dat BLUE RED 1 12 h 0 3 5 5 2 Simple profile load Profile data can be loaded in Magpick using profile list file This method is certainly beneficial when large numbers of similar files tens or hundreds are to be loaded However profile list
361. y a where a is the scaling coefficient from meters to other units Thus in case of feet a 3 2804 and magnetic moment is scaled by 35 3 13 UTM Gauss Kruger transformation in magpick OBSO LETE MagPick is supposed to work with local projected magnetic data Usage of geodetic coordinates is possible but depreciated Instead the user should project his or her data into the UTM Universe Transverse Mercator projection or any other suitable projection UTM is supported by MagPick 121 UTM Gauss Kruger transformation OBSOLETE internally False northing and easting should be introduced to avoid large numbers MagPick stores the position as single precision numbers allows double the amount of data loadable into program The full UTM form as well as geodetic would lead to lost of accuracy Allows you to save and load projection parameters from file It is recommended to keep this file with the data Set of ellipsoid names to choose from Major axis and flattening are changed when you change ellipsoid to reflect your choice Ellipsoid s parameters If you choose Ellipsoid name wos 84 1984 User defined you can enter these values Major axis m 6378137 00000 If checked central meridian will be Flattening 298 25722 taken from first Lat Lon sample UTM calculator will show zone and C M Warning if you do inverse transform only Y Get central meridian from 1 st sample do not check this box
362. y anomaly as dipole or monopole lTerms dipole and monopole are widely misused in geophysical community to describe shape of the curve In reality dipole is infinitely small magnetic object and magnetic monopoles simply do not exist 139 90 Single magnetometer inversion 18 Using single magetometer data for inversion in MagPick For the single mag inversion magnetic field anomaly should be recorded on multiple passes lines with line separation comparable with distance to the target In example here mag altitude is about 7 8m with line separation is 20m which is OK but not perfect for purposes of the MagPick inversion Generally speaking magnetometer data should be clean of diurnal time variation which means that base station magnetometer or other means of Earth s field time variation recording should be available In the example here we do not use diurnal correction which is an omission The key point point of the inversion is that multiple lines should be involved Consider the following data set 89 8500 8600 8700 8800 8900 9000 9100 8500 8600 8700 8800 8900 9000 9100 Figure 89 Profile lines recorded with single sensor Here is line 5 red has anomaly of interest which is shown by stack profile To use this this anomaly for inversion we also need to include lines 4 and 7 which are adjacent to the line 5 Look at the anomaly plot 90 for line 5 in the Profile view window
363. y depth from the sensor can be computed 158 HVDC cable inversion 4 d Model background Could be DC constant linear or square function e Initial XY seed Selection are automatic and picks In case of automatic poly line inter sections are used In case of picks user should put picks on the map f Initial cable depth Enter expected cable depth The reference could be from sea floor water surface or sensor depending on how to report depth selection above Miscellaneous a Use sensor depth If this box is not checked program assumes all data have constant zero depth b Use altimeter Use values O for altimeter 1f not checked c Smooth sensor depth with spline If this is checked program smooths depth readings before carrying out the inversion d Depth smoothing parameter 1 e 4 is recommended e Total non linear optimization iterations Default is 2000 might not be reachable f Derivatives Use analytic or numeric derivatives for non linear optimization Analytic is supposed to be faster g Create protocols and protocol folder If this box is checked user should define a folder where all results of the inversion including observed and synthetic fields are saved to be used for future plots or reports By default program only saves results of the inversion but no fields 20 3 HVDC inversion Results Results of the inversion are presented in the dipole worksheet gt The worksheet has the fol
364. you may encounter e The date you entered is out of model scope 1900 2005 presently Obtain a new file igrf dat and replace the old one e The program can not find file igrf dat Make sure this file is exists in the same subdirectory as the MagPick executable Make sure you call MagPick with the full path or its location is listed in system PATH variable 124 Potential field transformations 15 Potential field transformations In many cases the total field anomaly can be treated as a potential field which allows the use of some standard transformations These are upward downward continuation pole reduction decomposi tion of the total field into its components All these transformations are based on the Fast Fourue Transform FFT and are available in MagPick To learn more about the theory of these transformation please see 7 Due to the nature of an FFT transformation you can get a considerable side effect if your grid has a small number of cells or if you have a considerable gradient across your area Attention All these transformations are working with anomalous magnetic field NOT with the total magnetic field measured by the total field magnetometer Before using of any of these transfor mations you should subtract average field value of IGRF predicted value from your data 15 1 Upward continuation Because of the potential nature of the gravity and magnetic field they can be calculated at any el evation above and in
365. you might conclude that you are unable to find this object perhaps this object is not a pipe This is also a possible result You may note that the estimation procedure here is less stable than one for the dipole If you set the initial location far from real and or with weird initial depth procedure is likely to fail Conclusions Hopefully you have learned how pipe parameters can be estimated using MagPick I would like to stress that this feature has not been in wide use It appears much less stable than the dipole estimation I would recommend to use it only when there is a clear field picture as presented in this tutorial 237 Tutorial 27 7 Reduction to the pole Field at point with declination 30 Inclination 70 degrees Field on pole declination 0 Inclination 90 degrees 20 40 60 80 100 120 20 40 60 80 100 120 Figure 166 Reduction to the pole Preface It is a well known fact that the total magnetic field measured at a arbitrary latitude and longitude can be reduced to the field measured on the magnetic pole To do this kind of transforma tion the user should know the magnetic inclination and declination at the point of measurements use IGRF model to find it Also the direction of the body s magnetization is needed This last value may not be known however in some cases it can implied that the body has only induced magnetization and therefore it s direction will coincide with the direc

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