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1. Geese Ee iiini cee EO 53 8 48 8 I a pees mmm 4 4 a zm a E E a paper iii gt ae gt Lp co ee a a l lee ecd Se ee d gue i o E r zm d je canas zm earannan aaa gt PS a a el Bc ES Tapper a PHP If there is an obvious misplacement use Undo to return to the previous position data display In this example all data positions are now in State Plane coordinate system Example 2 Local 858 X Y positions and Global State Plane or GPS coordinates are known for 4 or more corresponding points This is a mote common case where the corners of the area are measured with GPS Then the new data position coordinates are simply recomputed from one coordinate system to another The program does not try to account for any 858 system positioning irregularities Four points known in both coordinate systems are sufficient to derive the transformation The new points need not necessarily coincide with any of 858 survey marks The requirements are that no more then two points can be connected with a straight line we are defining a new surface A Pseudo Affine transformation is defined in the formulas below X For example X Y would
2. m r n NN i Figure 47 To deselect all the positions click the left mouse button anywhere 4 5 2 Editing a group of positions Once you have finished selecting the positions click the right mouse button on the green area of the map A pop up menu should now appear on the screen EE hPUunmumitstud l wu i Figure 48 e To shift the selected positions by an X or Y offset select Shift Selected Position s By e To delete the selected positions select Delete Selected Position s e To line up the selected positions along a slope select Line Up Selected Positions Along A Slope The following segment operations are only available for continuous surveys e To shift the selected segments by an X or Y offset select Shift Selected Segment s By To reverse the selected segments select Reverse Selected Segment 5 e To reverse and shift the selected segments select Reverse And Shift Selected Segment s by e To delete a segment select Delete Segment This will delete the readings of every selected segment Once you have selected the operation to perform one of the following dialog boxes will appear 70 4 5 2 1 SHIFTING A GROUP OF POSITIONS Shift position s Figure 49 Type in the X and Y fields the distance for every position to the new location then click the left mouse button on the but
3. Hold the Crt key to select multiple channels at once The Select channel to add dialog box will be closed and the channels added to the data channels list To remove an already selected channel highlight it and press the Remove button To remove all channels press the Remove all channels button How to load This dialog box controls and constrains the type of data that can be loaded into MagMap Typically the user needs to load both data and positions however it 1s possible to load disparate data from separate files as it described at the beginning of this section Select appropriate type here Based on this selection some input fields in the dialog are grayed out for instance if only positions are loaded the data section is disabled if only data is to be loaded then the position section is disabled Several data only and or base station files can be opened simultaneously to over different time spans This would normally be used when you have a multiple day G 858 or MagLog survey with base station files that begin and stop each day Then you would load the entire field sutvey and several base station files to apply diurnal correction on a day to day basis Keep in mind however that multiple base stations which were positioned at different locations will have different base offsets and your final corrected data set under these conditions may need to be block leveled Observing the base station data files concurrentl
4. Figure 1 Drop down menu shown on profile plot The above screen shows the selection of the flag using the menu obtained by right clicking on the spot where you would like to place the flag Once you have placed a flag you should see the following 72_100 bin 2 Figure 2 magnetic profile after flags have been added 108 72 100 1 nnnnnnnnnnnnnnmi 1 m m m m m B m mM gm mM mM M HM M g EE EE EN ON ON JN Figure 3 position map with corresponding flag Note that the 1 shown on the magnetic profile corresponds to the 1 shown on the position plot If you want to make a flag on the GPS plot you need to bring up a magnetic profile corresponding to the GPS map In the above example we do this by selecting the GPS menu and then selecting Draw new map using GPS data and the features of a Maglog NT survey You should then see a GPS map and the corresponding magnetometer data 72_100_bin Figure 4 GPS map with multiple flags Note The magnetometer data associated with the GPS positions is treated differently than the magnetometer data associated with the G 858 flags and positions Thus you need to choose the appropriate magnetic profile that corresponds to the map you want to flag if you want to use the G 858 map then click on that map to get the appropriate data and if you want to use the GPS map use the data associated with that map This also applies to any 109 data
5. Left clicking the mouse button again on the data set number will enable this data set to be downloaded 3 1 3 4 SETTING FILE NAME TO SAVE AS Next to the data set number you should type the drive directory name and the name of the file you wish to save as on the PC By default data set number 1 will be saved on the PC as C Program Files Magmap dataset bin Where C Is the drive letter Program Files Magmap is the directory name Datasetl bin is the name of the file You can type any valid drive directory and filename but you should try to use the extension bin for the filename The extension bin indicates this is a binary compressed file downloaded from a G 858 and is what Magmap expects You will see later that you can save your survey as an ASCII STN file In any case you should always keep this binary file You cannot edit this file By caution after downloading your survey you should back up this binary file Given the cost of your survey it is worth doing this extra step If you wish to browse your computer to select another drive or directory left click the mouse button on the browse button A standard Windows 95 Save Dialog Box will appear on the screen 3 1 3 5 SETTING DOWNLOAD ONLY DECOMPRESS LATER The data downloaded from the G 858 are in a compressed format If you wish only to download your sutvey and not process the survey data now you can keep your sutvey in th
6. Note that the user can use any characters to separate fields in the date string except digits commas tabs colons and spaces For instance 10 12 1998 is perfectly correct time stamp Year can be recorded as full year as 2007 or as short year 07 Years less then fifty are to be considered of 21 century years more than 50 belongs to 20 century Examples 07 is 2007 77 15 1977 e Line information MagMap searches the file header for the word line to use that column as the line number However you can always select a different column for line number as appropriate If no line numbers are available you can display the data as one line check Don t use lines or you can automatically assign line numbers based on the distance between neighboring positions check Split data file into lines by distance and enter Split distance When distance between two sequential reading positions exceeds the split distance MagMap automatically starts a new line and increments the line number e Data channels The last step is to specify which columns contain the magnetometer data The Data channels list will list the columns selected for import Press Add data channel and the following dialog box appears with all data columns listed Select channel to add 44 Select the magnetometer data channels for example could include magnetometer field data signal strength depth altitude etc and press
7. This includes e Surveys done without GPS only mapped coordinates available e Surveys done with GPS where you drew the GPS map using the option Draw new GPS map using the features of a regular 858 survey To export your survey to Geosoft Analysis and Plotting Software or Surfer you must have an open survey file When several survey files are open you must select the survey you want to export by selecting the window just click the mouse button anywhere in the window If you used a base station and want to do a diurnal correction to your data you must also open every base station file which covers the range of times desired Once you have an active survey select Export from the File menu item or right click the mouse button inside the grid and select Export from the pop up menu The following export dialog box Figure 69 will appear on the screen 167 Export Setting One sensor 1 or left or top or front Geosot 11 x v sensor wm ee PVE Program FilesiMagMap36Y SAMPLES survey xyz j Figure 69 12 1 1 Setting the type of survey You can change the grid parameters that you already entered as described in paragraph 3 4 page 46 In the case of mapped survey mode you can redefine your grid This will change the coordinates of every position acquired in your survey You should only use this feature if you set up invalid grid information in the G 858 magnetometer before doing y
8. 57 4307 37 4306 37 4305 122 195b0 122 1858 122 1850 122 1854 2 122 1852 122 1950 122 164838 Ctri left mouse drag to Zoom Press r to reset 11 40 57 11 41 01 11 41 04 11 41 07 11 41 11 II The Problem Sometimes there may be spikes in the data that are hard to filter using the Despike feature of MagMap We have now added a much more powerful despike editor called the Range Despike editor The Solution With the profile plot on the screen go to Filter then Range Despike You will see an icon appear that will allow you to draw a box on the plot with your mouse data that exceeds the minimum or maximum boundaries of the box will be cut from the data set but only with in the lateral boundaries of the box This gives fine control as well and sweeping editing abilities to the user 2000 E Selected range despike limits are 49356 29 49747 74 Would you like ta proceed with range despike After Despike After the Range Despike editor has been applied the data is now modified and the results will be shown in the Contour Map and when 1 the data is exported to Surfer MagPick or Geosoft for additional m l processing This is a quick and easy way to clean up the occasional Spike or dropout III The Problem Basestation data some times has noise that should be smoothed prior to applying diurnal correction MagMap2000 now offers a basestation sm
9. GPS menu item and then Draw new map using GPS data and the features of a Maglog NT survey Draw new map using GPS data and the feature of a regular 859 survey Draw new map using GPS data and the features of Maglog NT survey setup PS otteet We picked this option because we will need to add a position offset to our data our GPS and magnetometer are not located in the same place This option will allow us to do this We should then have the following two files 200 HEEL m pot pus m p pd I e po ne port T port p NEM i p Lm pt pM M ut a GPS data Magnetometer data 17 3 4 Editing the GPS data We now want to edit the GPS data Recall that the mapped file had some lines we needed to delete We know that the last line definitely has bad data We also know that there was one line that was done twice 201 Additionally we will want to add a position offset to account for the magnetometer being located 1 6 meters in front of the GPS We would also like our final map to be in UTM coordinates 17 3 4 1 DELETING A GPS LINE In this file we can safely ignore the line that was done twice because the position data is still okay For the GPS data if a line was done twice the GPS will report the same posi
10. 207 Magnetometer data with drop outs linearly interpolated There is also a downwatd spike in the middle of the screen that appears suspect We can choose to despike the data using a spike value of around 500 spikes of 50 are common but this won t do anything If we look closer e g run our cursor on the readings and see different values for different times we notice that this spike actually consists of several changing readings in other wotds it is not a spike at all Thus we are finished with our magnetometer data 17 3 6 The base station file This section describes some operations that we can do with the base station file Normally this file requires very little attention it is only used as a stationary reference to compare the magnetometer data to 17 3 6 1 LOADING THE BASE STATION FILE We can load the base station either as a binary file or as an ASCII file if you have already converted it In this case we will load the ASCII equivalent 208 To open the file you can select it as follows Open Look in Ex Wagl 32 n AL str ngU 7L str nra PL str File name base stn Files of type G 858 Asci Files stri Cancel Note You can open other files you saved earlier in the same way From here you should see your base station data base stn Base station data 17 3 6 2 CHECKING THE BASE STATION DATA If we look at the file it is difficult to see if the data 1
11. REAR WHEN WALKING ACCORDING TO FORWARD DIRECTION You had two sensors second sensor in front of the first sensor You want the longitudinal gradient with the rear sensor magnetic field subtracted from the front sensor magnetic field when you walked according to the picture defined in FORWARD DIRECTION For example if you set the FORWARD DIRECTION to the first item line going up in the increasing Y direction Every survey line going in that direction will have the gradient computed as the following front rear Every sutvey line going in the opposite direction will have the gradient computed as the following rear front 12 1 1 9 2 SENSORS TO COVER 2 LINES You had two sensors with the second sensor on the right of the first sensor You do not want the horizontal gradient but instead assume that each sensor covets one line to get a better land surface coverage Often used for archeology and UXO sutveys 12 1 2 Setting bias for magnetics If you have selected a gradient survey you can add or subtract to the gradient a constant magnetic field In the bias value for magnetics just type any positive or negative value you want to add to the gradient 12 1 3 Setting the sensor separation If you have selected a survey with two sensors type in this field the distance between the two sensors this unit should be consistent with the survey position units 170 12 1 4 File format You can choos
12. c an OFM Im Ctrl left mouse drag to Zoom Press r to reset 90 Note The aspect ratio has not been adjusted This contour plot was done before any data was filtered or drop outs removed Thus using conventional techniques this plot should have been entirely one color using the number of colors available for the same reason as discussed earlier However in this plot blue spans about 400 nT whereas green spans about 8 nT still each color appears about the same amount on the graph Thus the technique can be summarized as the range for each color is picked in such a way that each color is represented the same amount on the graph 5 1 3 Plot options for 2D 3D plot 5 1 3 1 SET MIN MAX FIELD Right clicking the mouse button inside the window will bring up the following context menu Plot Sensors Setup Plot ell Set Min and Max Field Set Grids 20 30 Plot Only Selecting Set Min and Max Field will allow the user to change the maximum and minimum Z axis scaling Type in the range of values you interested in and press OK button when done This will repaint the window using the new defined maximum and minimum fields The legend to the right will be updated at the same time Clicking on Restore Default button will reset maximum and minimum fields to be default values Ser vertical Scalig Ed Maximum field 50847 6484375 Minimum field 17763 3164063 Restore Detault
13. i i ddl Program Files MagMapdb datasets bin 3 1 3 1 SETTING THE COMMUNICATION PORT First setup the communication port that your G 858 is connected to You can either select COM1 ot COM2 Make sure you did not select the communication port where the mouse or external modem 1s connected 33 3 1 3 2 SETTING THE BAUD RATE The G 858 supports different baud rates ranging from 1200 BD to 115 kBD and an auto mode Auto Detect where the PC will select the best baud rate For most cases setting the Baud rate to 115kb should work just fine If you are having problems downloading your survey at this baud rate with lots of retries lower the value to 19200 or smaller Once you exit Magmap your settings will be saved You do not need to set these values again unless you connect the G 858 to a different port or are having problems at high baud rates 3 1 3 3 SELECTING THE DATA SET In the G 858 you cannot store more than 5 surveys at any time Each survey is represented by a number from 1 to 5 that correspond to the data set number By default every data set is selected to be downloaded check marks near the data set number To prevent a data set from being downloaded click the left mouse button on the check mark of the data set you do not want to download The check mark should now be removed and the name to save as and BROWSE button of the corresponding data set grayed out
14. It is recommended that you use grid lines before printing Note that the appearance on the paper greatly differs from what you see on the screen 5 7 Marking anomalies for further study In the course of a typical Magmap analysis you usually will use at least two windows one showing the positions involved in your survey and the second showing a profile of the readings over time Itis often useful to be able to correlate an interesting feature seen on the reading profile with the positions given in another window This can be done by the use of flags 107 The flags placed on the profile will stmultaneously appear on the position map and on the contour map allowing the user to place the cursor on the flag on the map for instance and easily identify the anomaly s position This feature works in either X Y or Lat Long spatial mapping configurations 5 7 1 Setting a flag To set a flag you need to have an X Y map default screen for G 858 surveys or a map with GPS positions From here you may click in an empty area but inside the survey grid area and select Plot Mag Field This will bring up a profile plot of the readings Once you have the profile plot you may right click on part of the map that shows the reading that you would like to locate on the position map 72 100 bin 2 Fle Ea Plot Sensors Setup Plot All Sensors Set Min and Max Field Get 20 20 Pict mny Set mark Remove all marks
15. JE Projects M anuals h agmapSb E sample Files o60 E NO VALID BASE STATION FILES ARE CURRENTLY OPEN H SIR AN IF vau did setup a base station while doing a survey ANALOG DEVICE 2 Please first open the base station file s from the menu ANALOG DEVICE 3 ANALOG DEVICE 4 ANALOG DEVICE 5 ANALOG DEVICE 5 ANALOG DEVICE 7 Export MagPick profile Initially read every samples from MagPick caen In this case we have chosen to expott this in Surfer format Additionally we do not want to export data separately this would keep the GPS and 880 data in separate files so we have unselected Export Data Separately to Default Filenames By default all fields are highlighted and exported If you don t want to export all of the fields you can hold down the C7 key and select the fields you would like to export as seen above The final file should look similar to the following magl X magl Y mag2 X mag2 Y ANALOG 1 ANALOG 5 TIME DATE 0 14 30 11 un 40 11 429996 34700 30000 1700 13 35 57 000 12 12 98 0 13 29 09 0 25 39 09 49998 60500 49999 47400 13 35 57 100 12 12 98 0 11 28 07 0 24 38 07 50001 78000 49999 97900 13 35 57 200 12 12 98 0 10 27 06 0 22 37 06 49998 59200 50001 06000 13 35 57 300 12 12 98 0 08 26 04 0 21 36 04 49999 60500 50000 99200 13 35 57 400 12 12 98 0 0 6 25 03 9 99409 300004420500 50000 01600 13 35 57 500 12 12 98 0 0 5 24 01 0 18 34 01 49999
16. but some of the dialog boxes and windows will not look as pictured in this document 1 3 Installation 1 First decide to which drive and directory you wish to install the program It is prudent to keep it in the default directory C program_files magmap2k 2 Insert the installation diskette into your floppy drive 3 Run the SETUP program found on that disk There are several ways to do this One is to double click on My Computer double click on the floppy drive then double click on SETUP Or click on START then select RUN Type A SETUP and press ENTER 5 Follow the directions on your screen 1 4 Usage The three modes of operation of the G 858 correspond to different ways of manipulating the data inside the Magmap program 1 4 1 Base Station Magmap will download the base station data plot it and use it to correct the survey data for diurnal drifts You can determine that you have a valid base station file that overlaps with the field data by going to your export menu If you do not have the message No valid base station file has been opened at the bottom of your export menu this means you have a valid base station file 1 4 2 Simple Survey You must describe your survey to the Magmap program so that the program can properly locate the data points You will manually input the starting line direction the line and mark spacing and whether you took data bi directionally 1 4 3 Mapped Su
17. 01 09 12 24 730 163 HEROT 17 5 A 18 06 23 01 09 12 24 746 The task is to have both fields HEHD T and HEROT interpolated to the magnetometer time and appear in the interpolated output file as two columns Procedure Press Add data file on the Wizard s screen and select GYRO compass file Enter prefix HEHDT in the prefix field enter the channel number as 1 and type the channel name as Heading Then press Add data file again and select the same file Now use 5HEROT as prefix set the channel as 1 and the name as Rotation With this setup the program will read the input file twice once taking only heading strings and a second time taking only rotation strings Both these variables are interpolated to the magnetometer time and appear in the resultant file as two separate columns with the names Heading and Rotation 11 2 4 Select UTM transformation parameters The second panel allows input of UTM translation parameters Select UTM transformation parameters vw Transfer Lat Lon gt UTM on input Transfer LITM Lat Lon on output Ellipsoid parameters Ellipsoid User defined Major asis m E3781 a Flattering 298 254 UTM projection parameters Central meridian degrees U v Choose central from data Scale factor 0 9666 for 0 9996 False Northing m 0 False Easting m lo 5 ava Load lt Back Cancel The Transfer Lat Lon gt UTM on i
18. 1 281 122347 OG 2535040 The values are line number Julian day time station number and magnetic field reading to one tenth decimal not shown G 858 53504 000 0 000 13 59 00 000 07 06 99 0 The values are an internal tag number indicating type of data first magnetic field reading second magnetic field reading zero unless using a second sensor time date and a second internal tag number The base station data file time period must be equal to or greater than that of the survey data file At a minimum the file must contain two data points at times equal to or greater than the start and stop times of the survey data file It is possible to use SURFER file for base station readings File should consist of at least three columns readings date and time 117 7 Processing magnetic field readings 7 1 Introduction Despiking is a technique used for removing readings known to be incorrect These spikes are usually identified because they differ significantly from the adjacent readings They can be caused by operating the sensor near the dead zone under high tension lines and or over sites where there is a high accumulation of small magnetic surface clutter and the operator is carrying the sensor just a few inches above the ground surface However often anomalies can be mistaken for spikes so we need to develop a scheme that allows us to distinguish anomalies from spikes One criterion that we can use to distinguish
19. 12 13 22 Export Setting File Format Surer Iw Export Data Separately to Default File Names Select Output Path File Name Browse c datas 17 dat NO VALID BASE STATION FILES CURRENTLY IF did setup a base station while doing survey Please first open the base station file s from the menu Select Fields ta Export DOP HEIGHT LINE MARE TIME DATE speed kntots 1 88 IN z Export flaggedipoints only Cancel If data is exported into separate files with default file names prefix is used as part of this filename except non alphabetical characters such as in this example This example speed values is mostly for QC purposes for instance one could check what was actual speed during the survey More practical example would be to use height measurements from GGA 155 message Those are taken in already but only if other data such as magnetic field is present Let s assume the survey where GPS 15 the only device and the goal is to plot an elevation map Loading GPS data into MagMap as usual and then loading GPS again as prefixed data can achieve this 156 Note This may not work as expected if GPS during the survey loses some of the fields in its GGA message for instance due to poor satellite coverage This will shift channels in the message and some other channel can substitute height which is not desirable 11
20. G 858 ASCII file that has been decompressed with the DOS version of MAGMAP you will need to select the type of survey you did as described in the following dialog box Figure 5 Otherwise if you are opening a G 858 ASCII file that has been decompressed using the windows version of MagMap called Magmap you will not be prompted for this dialog box as the survey information has been stored in the ASCII file 858 Survey Information Mappedsurvey 1 jeg survey Base station Figure 5 Once you have selected the type of survey you did click the left mouse button on the button and your survey file will be read as shown on the next dialog box Figure 6 38 Loading G 858 Ascii File Figure 6 The line number of this dialog box indicates a count of lines of text of the file being read in and not the sutvey line numbet 3 3 3 Opening a G 856 survey ASCII file If you are opening a G 856 ASCII file you will need to select the type of survey you did One sensor survey Gradiometer survey or base station survey as described in the following dialog box Figure 7 You will also need to set the year in which the survey was started This is because the G 856 stores the date as the Julian day e g Day 221 out of 365 is recorded as 221 856 Survey Information Figure 7 Once you have selected the type of survey you did click the left mouse button on the OR
21. Global system employed If the box is checked the program uses an ellipsoidal approximation and computes distances in meters using Lat Lon pairs It is the user responsibility to select correct type of coordinates Selecting Lat Lon when the actual data is in UTM or State Plane would result in huge DX DY and Distance error values If there are only four points all errors are zero Each time you add a point modify or remove a point the transformation coefficients are recomputed new solution coefficients are displayed and DX DY and Distance are updated It is advisable to save this table into a file use Save Points button for future reference File format is shown below 4 X GLOBAL Y GLOBAL X LOCAL Y LOCAL 7605249 7253704 417 921 7604839 7252787 The first line of the record is the header and is omitted Note that the file format is compatible with the format used to replace all the marks Example 1 These two files are interchangeable After the transformation is completed press Ok and the transformation information 15 read into MagMap All points on the screen are replaced with new positions If there is an obvious error use Undo to revert to the earlier screen The general recipe in this case is that if a few points are known to have accurate positions use them If you are not sure of the accuracy of your positions use as many points as you can to minimize errors through least square fit Note that i
22. If you save a GPS map window only GPS locations and magnetic readings will be saved Positions field notes and pause events will not be saved If you save a regular map window using mark location only position locations and magnetic readings will be saved GPS data field notes and pause events will not be saved You should never save a file with the same file name as your original file If you wish to process the data yourself or if you write a program that reads G 858 ASCII format you can use the DOS utility program bintoasc exe that is shipped with Magmap It allows you to decompress a G 858 binary compressed file to G 858 ASCII format For more information type bintoasc exe at the DOS prompt 176 14 Printing Magmap allows you to print any Magmap window There are also a few options available that will help you print e You can change the title of a plot by clicking on the middle of the title on a window This is useful when you need to distinguish different plots e You can see a preview of your printing by choosing Print Preview from your file menu It will immediately show you a preview of how your hard copy should differ from your screen layout Namely Magmap will set a white background and scale the picture to occupy most of the available space This will allow you to have reasonable layout but it will prevent you from using exact scaling Additionally for contour maps the coordinate mesh will be
23. SETTING Cancel ERFURT NOM In this case we have chosen to export the position sensor reading and diurnally corrected sensor position to a file named 0 70 dat We can export this by pressing Export Now Note Even if there is GPS data present it will be ignored in this case You need to select an active GPS window in order to export GPS data GPS and mapped data are always treated separately 18 6 Further data manipulation The second file is processed much like the first There are no huge spikes in the data and the map is correct Therefore you should be able to easily load the base station file load the data file and export without having to do anything else 228 Make sure that you export this file with the same output parameters Refer to section 17 5 2 for information on how to concatenate the output files 229 18 7 Analysis in Surfer This section assumes you ate familiar with basic operations in Surfer If you are not consult the Surfer manual for discussions on the plots used 18 7 1 Using the contour and shaded relief plots As done in Chapter 17 we find the shaded relief plot to provide a useful view of our data We get the result shown below s 014 jJ EL ILI 0 Oo DO num S000 DOO Shaded Relief plot with mapped data We can easily make out the pipe features on this map We can also see several other anomalies on the map This
24. THE CONTOUR AND SHADED RELIEF PLOTS GETTING A POSITION OF THE ANOMALY FROM THE CONTOUR PLOT ADDITIONAL OBSERVATIONS INDEX TABLE 221 223 223 223 225 227 228 230 230 232 233 234 Note to new G 858 Users This software replaces the DOS version of software also included with the G 858 In some cases G 858 and G 856 magnetometers were shipped with an early MSDOS based version of MagMap We strongly recommend that users upgrade to Windows 95 98 2000 or NT in order to employ the full power and utility of Magmap In keeping with the common naming conventions this manual refers to Magmap and the newly released MagMap2000 New features will be added to the MagMap2000 version in our continual pursuit to deliver the highest levels of support to our customers in their quest to see beneath the surface of the earth 22 1 Whatis Magmap agmap is a post acquisition processing software used to analyze and process data from a number of different instruments It allows the user to download data from the G 858 and modity the positions that were entered while doing a survey It also supports other instruments such as the G 856 G 880 G 881 G 877 the Ohmmapper MetalMapper and the EM 61 The resulting data grid is graphically displayed on the PC screen as a Quality Control measure and to assure coherence between the original acquisition parameters and the final locations Editing functions include moving lines and pos
25. Use this dialog to re assign channel order and names If any of the assigned channels are defined right pane of the dialog is not blank they are used in place of defaults In no channel is specifically assigned right pane of this dialog blank then default names from the left pane are used In this example we only want to get speed in knots channel 2 so select CH2 on the left and press Add button Type desired name as shown no spaces please Assign name for 2 q X Mew channel name speedikntots Cancel Then press O amp button Dialog displays the change 153 Assign serial channels order and names X Existing channels Assigned channels CH1 LH gt speed kntats CH3 CH4 Remove all OF Cancel Press OK to complete assignment and then press OK one more time to load actual file Progress dialog is shown on the screen Loading prefixed data file X Reading line 24601 Disks File is loaded the same way as NT Generic serial device file When load is completed graph window is shown on the screen in addition to other data windows Note that you should not close this window till you complete data processing You can perform all kinds of operations with these data The window is shown here 154 10 39 03 11 09 04 10 39 03 11 09 04 Now when all other data loaded and is ready for export you can see speed in the export list 11 41 57 12 13 22 11 41 57
26. Zoom out X zoom out the map in the X direction only The scale in the Y direction remains unchanged Zoom in Y zoom in the map in the Y direction only The scale in the X direction remains unchanged Zoom out Y zoom out the map in the Y direction only The scale in the X direction remains unchanged Window Zoom zoom in map in the user selected window To select zoom area point mouse into one of the corners click and drag mouse to the opposite corner Zoom rectangle is shown with rubber band After releasing of mouse button selected rectangle is zoomed to extend s of the window Areas outside of selected rectangle are not shown To bring picture back to full extend press Fit in window button Fit in window the map is scaled to fit exactly inside the window X and Y do not have the same scaling factor If the window is resized the map will not be scaled again to fit inside the window Always fit in window the map is scaled to always fit exactly inside the window X and Y do not have the same scaling factor If the window is resized the map will be scaled again to fit inside the window True map coordinates X and Y have the same scaling factor When you zoom in a map you can use the mouse or the arrow keys to scroll the window 50 Right key Scroll to the right Left key Scroll to the left Up key Scroll to the top Down key Scroll to the bottom Page Up key Scroll one page up Ctrl Page Up
27. after or before main survey data To start loading prefixed data go to File Open menu and select file type as Generic Prefixed Serial Data as it is shown on the following screen shot 150 ES Export GPS dat EEExpart a 880 Ma dat Survey Of 17 07 Ist eS Export GPYTG GP S dat Survey 02 17 OF Survey Export 2 5 Survey O2 17 D7 Survey EH Export aP TG gyro dat Survey 02 17 07 Survey EH Export Serial Device cable dat Survey 02 17 Survey Files of type Maglog NT Files Cancel 385 Profiler 7 Magsea Projects ref Magsea Files MGS Files 3 858 bin amp file Metal mapper binary Files SURFER dat files nterpolator INT Test Then select file you wish to load for instance GPS file it also contains VIG messages Program will show preview of the file first 20 strings and allow prefix definition as it shown here 151 Generic Serial Prefixed Data X File name data02 17 OF SSurven 02 17 07 Survey GPS GP5 Data sample tGPGGA 181202 011 3800 206724 N 12224 965636 4 10 1 1 7 35 M 0 010139 D IRFHDT 3B5 TU 02 7 07 10 12 03 201 2 D27 0 10 12 03 20 GPQG64 181 202 511 3800 20710 12224 955401 4 10 1 1 7 36 0 01038 0 T00 02 47 07 10 12 03 551 02217707 10 12 03 BB
28. and y coordinates not identical 4 4 5 Plotting magnetic field readings of the entire segment For example if you plot all the readings of the second segment of line 0 as shown in Figure 10 you will get the following picture Survey bin Figure 39 For more information on this window see the section about plotting readings section 0 page 116 Readings are not shown in their correct linear position only in the sequence that they were taken This plot is used as a quality control device to insure that the data is free from excessive noise and dropouts It is very important to immediately remove any zero values or spikes from the data see section 7 After applying various filters the data should be re plotted for confirmation of results 4 4 6 Deleting a segment Delete segment ESES Figure 40 If the information reported by this dialog box confirms that this is the segment you want to delete click on the YES button otherwise click on the NO button to abort Deleting a segment will delete all the magnetic field readings acquired for this segment It may also delete the end positions if there are no other readings attached to these positions 66 For example in the survey plotted in Figure 10 if you delete the second segment in line 0 you will obtain the picture in Figure 41 Figure 41 4 5 Selecting and editing a groups of positions 4 5 1 Selecting a group of positions T
29. are set to the first four columns present in the file You will probably need to change the settings to reflect the correct columns used Click on the down arrow to select the proper data column Input file parameters Data File E Projects Manuals M agmapJ6 E xample Files S80 E Output File output dat 2 calum 1 magl X bd T column 2 magl Y id Field ealumn 5 ANALOGI m Line column if exists a E ANALOG 5 _ 7 TIME Use distance intervarto spi lt Back Cancel Selection of line column A few options to be aware of are 123 e Line column Destriping uses the line number column to determine which lines it is working on Select the proper column for the line number If the output file does not have a line number included you will need to select the option Use distance interval to split the lines e Use Distance Interval to split the lines checkbox This is used when there is no line number stored in the input file In this case you need to specify a distance interval to specify when a new line is started This distance interval is defined as the maximum distance between the positions of two adjacent readings E g if you do a land survey and have line spacings of 5 meters it is probably safe to put a value of 2 or higher for this reading If the value is too large it will not notice when you have shifted lines and if the value is too small it may assume you have started a new line w
30. be Global State Plane or UTM or new Lat Lon positions and would be in the local 858 X Y coordinate system If both coordinate systems are accurately defined a equal to zero and a a are equal to one Coefficients a a describe scaling transformation a a describe rotation transformation and describe 82 translation transformation between two coordinate systems Non linear terms a a describe inconsistencies in the application of the model after the transformations have been computed For instance if user defines local coordinate grid as 10 x 10 meter and wants to transfer it into State Plane which is defined in feet a a would be 3 28 scale coefficient between meters and feet If he or she converts to UTM defined in meters then a a would be 1 Furthermore if in reality 10 x 10 meter grid defined by the user is not square and for example is 9 6 x 10 2 meters other terms in the equation for X Y may also be used MagMap can use any number of points to compute this transformation The recipe is to use well defined points with minimal positional errors For instance in the picture below you would not use points 1 2 3 4 if you know that point 3 is misplaced 2 5 3 local coordinates of point 3 in x y will not show this misplacement The correct solution would be to use points 1 2 4 5 Point 3will still be misplaced after transformation and although nothing can be done here to correct its position t
31. button and your survey file will be read 3 3 4 Opening a Maglog project file The option Maglog Projects Survey will give you the option of opening files with an extension Survey This option is useful if you have a set of Maglog files and you want the program to automatically open all files associated with the survey you did After you have pressed OK it should automatically open all recognizable files types associated with the survey you took Note There are some files that Maglog NT produces that are not used in Magmap e g comment files Magmap will warn you that it cannot read these due to an unknown file type In this case it is safe to ignore this message 3 3 5 Opening an individual Maglog file You can open an individual Maglog file by selecting the file type Maglog Files You can then individually open each file associated with your project No user input is required when opening Maglog files except for Interpolator files using open as sufer dat etc 3 3 6 Opening a G 856 MagMap for DOS file This option will specify that the file you are opening 1s an old version of MagMap for DOS file 3 3 7 Opening a Magsea project This option is used when you have logged data from Magsea and have a series of files associated with your survey This option will automatically load all pertinent files and normally does not require any additional input You may get a warning message such as the one below war
32. fields outputted and the format look very similar to the Surfer file The only noticeable difference is the separate line that lists the line number This is updated later in the file 12 2 2 3 TEXT SPACE DELIMITED This outputs all the fields with one space between each reading 12 2 2 4 SURFER 3 COLUMN This export procedure is particularly useful when you have two sensors with corrected positions for each sensor and you would like to export into one Surfer compatible file Normally the easiest thing to do would be to export a file two times one file for the first set of readings and positions and the second for the second set of readings and positions You would then need to concatenate these two files We tried to save some work by creating this file format For each set of positions that you select you may select one reading This assumes that the first positions you specified will go with your first reading and the second positions you specified will go with your second reading etc If you don t have a position set to go with a reading or vice versa you will get an error message such as the one below Number of coordinate pairs should carespond to the number of sensors selected for export Please change your selection Export Setting File Format Surfer 3 column Export Data Separately to Default File Names Select Output Path File Browse E SwINNTSProfilesSAdministrataD esktap M a
33. have spikes that consist of several points far away from other points it may be difficult to smooth your data If the technique described above doesn t work experiment with the parameters and see if you can get a path that looks reasonable If all else fails you can always manually delete certain problem points and proceed from there 145 8 5 3 References on splines For more information about splines you can refer to the following The Theory of Splines and their Applications Ahlberg J H E N Nilson Walsh J L Academic Press New York 1967 e This book is out of print but can be found in some online used book stores e g BarnesAndNoble Com 146 8 6 Troubleshooting 8 6 1 Map appears incorrect when using geographical coordinates Occasionally there is a problem where an offset was put into the UTM setup UTM was disabled but the offset still remains Sometimes this will affect the map that is created The easiest way to get rid of this problem is to select UTM set both offsets to zero and select OK This will redraw the map in UTM coordinates You can then go back into the UTM setup and deselect this item and the map should be redrawn correctly If this doesn t work try exiting the program and reloading your file 8 6 2 Map appears incorrect when using UTM coordinates This could happen if you are using the wrong prime meridian Refer to the section on setting UTM parameters for a better description of solution
34. in Y e Zoom out X e Zoom out Y e Window zoom zoom in graph in the user selected window To select zoom area point mouse into one of the corners click and drag mouse to the opposite corner Zoom rectangle is shown with rubber band After releasing of mouse button selected rectangle is zoomed to extend s of the window Areas outside of selected rectangle are not shown To bring picture back to full extend press Fit in window button These are fairly self explanatory Once you select one of these menu options your cursor will change to reflect the type of zooming operation you are doing You can then zoom in on a specific point by pressing the left mouse button This zooming feature will remain turned on until you select the menu option again or deselect it from the toolbar You can go back to a view of the full map by selecting Fit In Window You can also get rid of all scaling permanently by selecting Advays fit in Window You can also zoom by using the toolbar buttons pictured below From left to right they are e Zoom in X and Y e Zoom out X and Y e oominX e Zoom out X e Zoom in Y e Zoom out Y e Window Zoom zoom in graph in the user selected window To select zoom area point mouse into one of the corners click and drag mouse to the opposite corner Zoom rectangle is shown with rubber band After releasing of mouse button selected rectangle is zoomed to extend s of the window
35. in the UTM screen as follows 203 UTH transformation setup W Enable UTM transformation m Ellipsoid parameters Ellipsoid name vwas 84 1384 Major axis meters Flattening UTM projection parameters Central meridian degrees Scale factor 0 9666 for UTM 0 9996 Northing meters 0 Easting meters 0 Cancel Note Here we let Magmap automatically set the central meridian After we ate done and press we should get the following map O 70_bin 204 As can be seen this map is in UTM coordinates but they are quite large and difficult to deal with We would like to have this in a local coordinate system where the bottom left hand corner corresponds to the coordinates 0 0 To do this we need to add offsets We need to look at the GPS screen in UTM cootdinates to get these offset values In the above case we need to have a northing offset of 4142942 21 and an easting offset of 572012 08 we took the negative of the numbers located in the bottom left hand screen Remember that we can find our offsets by using the formula e Value Offset NewValue e Offset NewValue Value if NewValue is 0 then Offset Value Here Value for northing was 4142942 21 and NewValue was the value we wanted to have namely 0 After we have set
36. is open it will update the display automatically Therefore the user can easily check how well the despike filter works using the current settings If the effect was not what was desired the user can click on the Undo button to reverse the filtering Clicking on the Close button will close this setup dialog box with the new settings saved in memory Therefore next time user selects Despike from Filter menu it will always use the current despike setting to filter readings The default value for peak threshold is 5000 and maximum spike readings is 1 Use despikine carefully for non continuous discrete surveys Readings may have been acquired far apart and therefore may look like spikes to the algorithm Note High amplitude noise variations usually occur over a very short time span Thus if you have an anomalous set more than ten readings there is a good chance that this is not noise 7 5 Destriping 7 5 1 Introduction Destriping is a new feature offered in MagMap 2000 which offers the user the ability to remove coherent heading error offsets from data collected in parallel line mode In addition the program can perform a smart high frequency filter along the line to remove the small sinusoidal noise associated with stride or quantization processes inherent in the collection of the data We define heading errors as errors that are dependent on the direction of travel When a survey is performed as a series of
37. key Scroll one page to the left Page Down key Scroll one page down Ctrl Page Down key Scroll one page to the right 21 00 survey bin ZO x I File Edit View Scale Filter Gps Survey Se Serer Gl M AM oo dod For Help pre IF 51 4 2 Selecting and editing a single position To select a single position right click the mouse button on the position symbol small blue square Figure 11 A pop up menu should now appear on the screen Figure 11 To perform the desired operation Move Position To Shift Position By or Delete Position move the mouse cursor on top of the corresponding item then left click the mouse button or use the keyboard arrow keys to select the item and press the ENTER Key To move the position to a new location select Move Position To e To shift the position by an X or Y offset select Shift Position By e To delete a position select Delete Position Once you have selected the operation to perform one of the following dialog boxes will appear 4 2 1 Moving a position to a new location Move Position mod Figure 12 Type in the X and Y field the coordinates of the new location then click the left mouse button on the button or pressed the ENTER key To cancel the operation left click on the CANCEL button or press the ESC key To switch between the X Y OK and CANCEL contr
38. map is useful because we can get a good view of where all the anomalies are We can also get a good idea of how deep they are by seeing how wide they are A large peak very dark spot on the contour graph or a large peak on the stack plot can be indicative of a large object or something near the surface The width of the anomaly will distinguish this An object buried close to the surface will tend to have a high peak but narrow width whereas the same object buried deeper will give a larger width and shorter peak This is discussed in more detail in the Applications Manual for Portable Magnetometers by S Breiner You can also start to make a guess about the nature of the object by looking at the contour plot Naturally objects such as pipes that lie horizontally are quite prominent on the graph You can make other general identifications by looking at whether the anomaly appears to be a magnetic monopole or a magnetic dipole For instance in the contour plot below we can see a number of dipoles and a number of monopoles 230 EL OO EL ILI ao 0 50 rr 1 0 20 OO zum DO nur S000 DOO Contour map of data We can zoom in on a few characteristic dipoles Selected dipoles from data These anomalies are dipoles that were produced by buried drums lying horizontally In each case the number and orientation of the drums differed as well as the depth In the lower right h
39. of 2 as shown below Shift selected seqment s Shift all selected segment s by pom 2 Cancel Shift Selected Segments menu In the new map we see that the lines we selected have shifted over by 2 meters 219 eek lll gp Ng ON HN HRS NI ITIN PF RV RIT NN Map with segments shifted Now we need to delete the last line where the battery went dead X 72 In order to do this we do the same delete operation that we did earlier We select the two position points and then delete the line BRR RRR RRR RR RRR RRR RRR RRR RRR RR Ree Rees De ee ee ee ee eee a CU NU Final map for X 0 gt 70 18 1 3 Saving current work At this point it is advisable to save the current work in case there are changes to make in the future To do this press Save Since we have not specified a save file before for this we will be prompted to type a file name As Save n E Wagl 32 d 0 70 Zi 0 70 str E ng 70 str Ej 72_100 stn Ez nmO 70 stn File name 0 70M ap str Save as type G 858 Files stri Cancel In the above example there are several stn files already present It will be helpful to pick a naming convention so that we can easily identify the files associated with a given open file In this case we chose to add to the initial file name We can save this by pre
40. only two positions 4 4 1 Shifting a segment Shift segment Figure 30 Type in the X and Y field the distance to the new location then click the left mouse button on the button or pressed the ENTER key The two positions of the corresponding segment will be shifted by the X and Y offset and all the magnetic readings inside that segment will be linearly interpolated between the two new positions For example in the survey plotted in Figure 10 if you shift by X 2 5 and Y 50 the second segment in line 0 you will obtain the picture in Figure 31 Mark 1 and Mark2 have been duplicated Figure 31 If you shift that segment again Mark 1 and Mark2 will not be duplicated 4 4 2 Reversing a segment There are three options for reversing a segment A segment can be reversed in X and Y direction in X direction only and Y direction only The last two options should not be used for horizontal or vertical segments For most cases select Reverse In Both Directions 62 Reverse In Bath Directions a4 Figure 32 For example in the survey plotted in Figure 10 if you reverse the second segment of line 0 you will obtain the picture in Figure 33 Figure 33 The positions at each end of the rotated segment have been duplicated in order to preserve the interpolation of the readings in the segments on either side of the rotated segment 4 4 3 Correcting a walking deviation There are two
41. or MagLog Pro surveys This feature allows the user to load virtually any ASCI columnar data into MagMap for analysis MagLog NT real time position interpolator files extension INT can also be loaded in this way Depending on the user selection the following information can be loaded from a SURFER data file 40 1 Positions and Data In this case it is assumed that each reading in the SURFER file has an associated position 2 Positions ONLY In this mode the user loads only positions 1 e the file is used in the same way as a GPS file in case of MagLog NT Survey files Magnetic or other data should be loaded separately and may have a different sample interval than the position sample rate Data can loaded as a SURFER file as well see below or as MagLog NT device file s While the user can load multiple data files only one position file is allowed Note that the Line Number file can also be loaded in this case 3 Data ONLY In this mode the user loads only data Multiple SURFER files can be loaded in this mode Positions and line numbers are loaded separately as MagLog NT GPS and Line Number file Alternatively positions can be loaded as a SURFER file see above 4 Use as a Base Station In addition any file of the structure with magnetometer and time information can be used as a base station file for diurnal correction as long as the dates and times of the survey and base file intersect base data must overlap ro
42. parameters for your shaded relief plot 94 Shaded Relief parameters Ea Iv Plot shaded relief map Sun azimuth 20 Elevation 45 Data scale 0 1 Cancel You need to select the option Plt shaded relief map to plot the map Your map will be plotted after you press and exit out of the Vertical Scaling dialog The sun azimuth and elevation parameters allow you to set the position of the light source in relation to the topographical map The data scale setting allows you to vary the height differences of the different parts of the topographical map A larger value of the data scale will favor large peaks whereas smaller values will allow you to see smaller variations better An example of a shaded relief plot is shown below Note this is obtained from the same data that produced the contour map shown earlier in this shaded relief discussion Plotting Mag Field in 2D Contours for Sensor 1 Ctri left mouse drag to Zoom Press r to reset 5 3 Stack profile plot 5 3 1 What is a Stack profile For certain surveys it is useful to view the magnetometer data of different lines at the same time in otder to look for trends that occur between different lines Since an anomaly 95 usually can be seen from adjacent lines we can distinguish anomalies from noise by looking at several lines We can also locate objects such as pipelines that extend over many lines Magmap s stack prof
43. the battery went dead 72 100 bin This file has the conclusion of the survey until X 100 Base bin This file has the base station data There are drop outs at the beginning due to a the magnetometer warming up 17 3 Analysis of magnetometer files 17 3 1 Loading the file In this section we will manipulate the two magnetometer files to get the correct mapped information We begin by opening the file The file type is G 858 Binary File as shown below Open Look in E Wagl 32 E 72_100 bin am Base bin File name 0 70 bin Files of type G 858 Compress Files bin Cancel Note This menu will default to the last file type you selected If you do not select G 858 Compress Files as shown above you will still get your data but you might not get your survey map You should get the map shown below 199 0 70_bin Ce er Initial map for first G 858 file 17 3 2 Manipulating the map In this survey we did have some problems with the map but we don t need to do anything to fix them We will use GPS rather than the marks and end of line manual positions to do our final positioning so we need to edit the lines that will be associated with the GPS file If you wish to read more about editing the map see the following chapter 17 3 3 Drawing the GPS map Now we would like to manipulate our GPS and magnetometer data To do this we need to make a GPS map We can select the
44. there is now a scale that has to span 50000 gammas compared to 5000 gammas when only one sensor is graphed Note Due to the above it is useful to de spike the data and remove drop outs from the data before you try to create a stacked profile Otherwise it will be difficult to make out small features in your profile Your final result should look similar to the stack profile below 2_100_bin a NC CC 5 3 3 Scaling a stacked profile The scaling for a stacked profile works the same as for all windows This will be discussed in more detail in the following section 5 3 4 How to turn Auto scaling off By default Magmap chooses scaling that will allow all the data to fit in one window In order to disable this and hence use the scaling buttons at the top of your Magmap screen you need to go to your Scale menu and deselect Advays fit in window Filter aps Survey oom 1 and m zoom Wut A and T eG Eres zoom Dr 7 EG 1 oon Br T Too oan EP ey epe n v Always Fit In Window True Map Coordinates arid lines You will then have the option of zooming in and out 5 4 Basic scaling operations You can scale the map a few different ways 1 Use the menu 2 Use the mouse and toolbar The menu options that will immediately change the scale are e Zoom in X and Y e Zoom Out X and Y e oominX 100 e Zoom
45. these errors by smoothing but it always becomes a factor when doing a sutvey Keep these factors in mind when you are planning your survey 233 19 Index table ASCII file 38 Base station plotting 112 Base station magnetometer 116 Baud rate 34 Binary file 39 BintoASC 158 contour plot 88 90 91 92 94 111 131 215 231 233 Coordinate Transformation 79 csv 36 40 175 179 180 DAT file 78 172 data scale 96 Decompress 35 Deleting line 60 segment 66 Despiking 119 destriping 122 Deviation line 57 segment 63 Diurnal correction 114 168 Diurnal parameters 113 Downloading 32 Downloading a survey 27 32 Dragging 141 207 Dropouts 121 Easting 138 192 193 Editing grid 28 74 lines 27 55 positions 27 52 segments 28 60 editing positions 27 elevation 96 234 Ellipsoid name 136 Export 31 78 169 File export 78 169 saving 177 Filtering readings 119 Filtering readings 31 Geosoft 31 78 169 GPS clock bias 140 GPS Interpolator 122 159 GPS Offset 139 141 174 196 207 Grid editing 28 74 Reversing 76 Rotating 77 settings 78 Shifting 75 Group editing 29 67 selecting 29 67 Host software 23 Importing a survey 32 Installation 25 Jump 143 Line deleting 60 deviation 57 editing 27 55 moving 59 reversing 56 rotating 50 shifting 56 MagMap Data flow 23 metal mapper 149 Moving line 59 Multipl
46. think about a Your data has obvious spikes that you would like to take out e In this case it is okay if your curve doesn t approximate most of the actual data You should aim to get a curve that takes out the effects of the spike The data that falls within the acceptable jump limits will not be changed This data will only be changed on the second smoothing Go to step 2 b Your data has random error but no obvious spikes e you should try to make your smoothed curve approximate your data as much as you can Try to determine what is due to error and what is true positional reporting and use small smoothing parameters to make your final path look reasonable You probably won t need to do any additional despiking or smoothing e g ignore Steps 2 and 3 if you get a reasonable curve Despike your data After you have your first smoothed curve choose a Jump parameter that will remove the spikes Smooth your data a second time If your path still doesn t look acceptable apply smoothing a second time probably to a smaller degree than the first In most cases you will be doing this after despiking so you will want to use a smaller degree of smoothing because your first smoothing had to take out the effects of the spike If your final path looks acceptable press Close and Apply 8 5 2 Warnings about smoothing Some paths are easier to smooth than others If you have data with many spikes or if you
47. 0 795 2 652 11 03 01 09 58 01 615 0 954 3 180 11209201 09 58 01 675 1 113 3 706 11209201 09 58 01 955 d Accept only stings with Please enter comma separated channel numbers and names Channel numbers fi 2 Channel names Fictation Heading Cancel The data file name is listed in the upper box and the beginning of the file is listed in File beginning box so the user can make decisions about which parts of the messageto use for interpolation Use the channel numbers dialog box to specify which channels columns are to be interpolated It is possible to specify more then one channel using a comma separated list Magmap2000 uses the same parsing rule as MagLogNT i e any character that is not a digit dot ot sign 1s interpreted as field separatot Names should be assigned to the channels using the channel names enter field Use a comma separated list to specify the names for more then one channel No spaces are allowed in the channel name designator box These names will appear in the headers of Surfer or GeoSoft interpolated output files The use of the prefix designator allows filtering of multi message files When the prefix 1s left blank all strings in the file are used for interpolation A prefix causes the program to accept only strings that start with the designated prefix Example Typical GYRO compass file acquired during marine survey HEHDT 180 3 1 25 06 23
48. 0 times longer than downloading the compressed binary file with the Magmap Import program and is not recommended Magmap Import provides an Autospeed function that will make RS 232 connections at up to 115 KBaud on compatible systems EM 61 data is treated like Magnetometer data OhmMapper data is processes within Magmap but is described in a separate manual PN 1 1 2 PC File Formats The transmitted binary data is stored in a binary file with the extension BIN on your PC This file requires about 100 KBytes of hard disk storage per hour of data collection at 10 readings per second The STN file is an ASCII representation of the data You can create this file at any point in your Magmap analysis and this can be viewed from an ASCII text editing program such as a spreadsheet Most editing functions can be accomplished with the Magmap program These files may be very large typically 1MB per hour of data collection 1 1 3 Accurately Positioning Data After conversion Magmap will interpolate readings between known position points called marks When you have GPS data each given position point will also count as a mark You have great latitude in defining how the survey data was acquired and in editing the individual positions of the readings Computation of the vertical or horizontal gradient from two sensor gradiometer files takes place at this stage During the location process the user may perform several corrections to the
49. 1 GPGG4 181203 011 590020749 N 12224954441 4 10 1 1 7 36 M 0010234 D r0 2 100 02210 10 12 04 152 GRP T7G 62 1 7 2 02217707 10 12 04 152 tGPGGA 181203 511 380020788 N 12224 955601 41071 1 seb E 4 02 17 07 10 12 04 553 O11 2 0247 0 10 12 04 191 204 011 3800 20828 N 12224 95257 w 3 10 1 1 7 37 OOO E fGPHET 66 5 7 00 0227 17 07 10 12 05 153 a GPVTGLBO BT MEDON TT 2b O27 P707 10 12 05 153 Pretix GPVTG Policy Accept data WITH Assign channel names Cancel To define prefix type GPVTG and select Po y as Accept data WITH prefix It means all other strings in the file are ignored As defined by NMEA VTG messages has the following type of information heading degrees from true or magnetic North speed over the ground knots speed over the grounds kilometers per hour As an NMEA message it also has checksum It means by parsing this message program will produce for channels Last channel checksum is meaningless Be default channels have names CH1 CH2 CH3 etc Those default names can be re assigned by pressing Assign channel names button Assignment dialog 1s displayed as the following 152 Assign serial channels order and names X Existing channels Assigned channels CH1 CH3 CH4 Add gt gt Remove all Cancel
50. 1 Export Procedure To export a survey select Expor from your Fz menu You should see the following menu File Format Surfer Select Fields ta Export POSITION MAMET ds 0 00 dy 0 00 POSITION MAMET r de 0 00 dus nr v Export Data Separately to Default File Names QUAL IND DOP Select Output Path File M ame Browse TIME E wINNTSM agmap96 Filename dal deis 1 G 059 2 NO VALID BASE STATION FILES ARE CURRENTLY OFEN Il IF vau did setup a base station while doing a survey Please first open the base station file s from the menu Export MagPick profile Initially read every f samples fram MagPick Export menu for Maglog NT survey This menu is quite different from the one that was discussed in the previous section One of the most noticeable changes is that you can output the additional positions specified in your GPS Offset menu The options you ate given are e Export data separately to default filenames This will export your data to separate files You should get one file per device Be careful if you choose this option This option will ignore any filename you type in e Select Output Path Filename choose any filename and path you wish to store your data in e Select Fields to Export Highlight all fields you wish to export The highlighted fields will be exported with a heading identifying each column You can select more than one field by holding down your CTR
51. 2 1 Introduction This utility is used to assign locations to large marine or airborne Maglog NT data files using interpolation of GPS positions Such large files are not well handled in MagMap and should therefore be processed in Surfer or Geosoft type programs Features e Processes binary and text data files e Text data files can be processed as original Surfer or Geosoft format e Original data files remain unchanged e Locations can be output as geographical or plane coordinates A choice of 12 pre defined ellipsoids or a user defined ellipsoid can be applied to UTM conversions e UTM parameters can be stored to and read from a text response file Magmap provides a wizard to simplify use of this utility It can be accessed by selecting the menu item nterpolate GPS wizard located in the File menu 158 11 2 2 Select Input and Output Files After you have selected nterpolate GPS wizard you should see the first panel of the wizard that allows selection of input files input file format output file and output file format Select input and output files Data File G ChinasT est repeat_line Survey 380 geal GPS File Chinas T est repeat_line Survey GPS gpe 3 Chinas T esthrepeat_ line Survey LineN umber G China T srh Orignal T m e Data file name of MagLog NT data file to be processed Most of the data files are in ASCII text format Data files from the GR 820 sp
52. 300 67 13 1 58 68 21 0 39 2 00 1 00 49658 80000 70 56500 11 26 37 As can be seen we have exported all of the fields that we wanted into a Surfer compatible format Note Some versions of Magmap2000 have problems exporting this file This is due to the fact that the file 0 70 bin was improperly terminated If you get a message that prevents you from exporting such as One of the lines is shorter than Look forward points Look backward points Export Aborted one work around is to not delete any lines on the GPS map It should work fine then 212 17 5 Further Data manipulation 17 5 1 Processing the second file The second file also needs to be processed This data has no noticeable spikes and the map 1s correct so the processing should be easy refer to previous sections for operations you might choose to do In this case we loaded the file drew a map using the GPS readings and exported the data no special manipulation required Make sure you select the same export fields as you did in the first file You should also pick a new filename to export to Make sure your base station file is open Note Many of the settings you selected in the first file will be valid for the second These settings remain e g GPS offsets UTM settings until you change them If you have difficulty graphing the GPS data e g the option is grayed out make sure that you have closed the first file Magmap cannot have two GPS maps of the
53. 5 good or not We see some drop outs which occutred when the magnetometer was warming up However it is difficult to see if the rest of the data was good We don t need to set any bias for the time because we set the clocks to be the same at the beginning of our survey Additionally we don t want to add any magnetometer offsets to all the data 209 We can re scale the data by pressing the right mouse button We fill out the following base stn EI X Maximum field 0 Minimum field ord Restore Default owe Our new map shows us that the data is okay except for the very beginning base stn el Eq Re scaled base station data In this case we don t need to do anything more to the data because these spikes occurred a long time before the survey began Thus we have done all we need to do with our base station file It is always a good idea to save it though 17 4 Exporting the data We have finished editing the GPS data and the magnetometer data We need to export this data so we can further analyze it To export this data we select the screen with the GPS data This is important because certain export options are only available through the GPS screen We can then go to the file menu and select Export This should bring up the following menu Export 5 etting Filesss AD 1 3240 70 dat Export Setting di
54. 858 bin files e csv file 2 You select both files to be opened You can do this by holding the CTRL button and left clicking on the applicable files After this you should see your normal position screen without your GPS data In this case we got the following which reflected the manual position points we took 178 sampcsv bin Opening screen after loading csv files 15 2 Looking at the GPS data 15 2 1 Drawing it as an 858 Mapped Survey Next we will look at our GPS data We can do this by selecting Draw new map using GPS and the feature of a regular 858 survey from out GPS menu We will be prompted to add some time corrections to the data This allows us to correlate the time reported from the GPS UTC with the time that the correction file is given in Greenwich time In our case we use the following GPS conection File name line gen csv Time diff Lacal P5 hours E Time diff Local sUTC sec dz 5 179 Our GPS data is shown below sampcs _bin niat rte E xA gt RETI gt m d AL d EN s 1 ti tuf ia p yuh TOT m tragen i LE P T m 1 or iz m GPS Screen with correct time corrections It is important to set these offsets correctly If they are set wrong e g we use 8 hours 20 seconds instead of the
55. 97800 49999 68100 13 35 57 600 12 12 98 Sample output file in Surfer format Note In the output format that we used in the example we would have to look at the data separately one magnetometer at a time or work with it further to concatenate all the readings You could instead choose to output the file in Surfer 3 Column format which would create three columns and would combine the readings for both magnetometers 197 17 Analyzing an 858 Land Survey with GPS Positions This section covers a sample analysis of an 858 land based survey that has GPS input In this sutvey we will look at the results obtained using the GPS readings as position points and also at the results obtained from doing a time interpolation between the endpoints of the lines This sample survey also has some common problems that might be encountered during a survey We will need to delete certain lines and de spike the data There is also base station data 17 1 Survey layout This survey had the following features 100 x 100 meter grid Lines were 2 meters apart Each line 1s 100 meters Additional position points were obtained from an Trimble AG 132 non magnetic GPS that was carried near the magnetic sensor A base station took data 17 2 File features We made three files during this survey 198 0 70 bin This file has all measurements for the first 36 lines up until X 70 e At X 52 one line was mistakenly repeated At X 72
56. Areas outside of selected rectangle are not shown To bring picture back to full extend press Fit in window button 101 e Fit full map in window but keep scaling options enabled e Always fit full map in window e Use true map coordinates 5 5 True map coordinates Usually when you select Fit full map in window Magmap will show you your entire map and use the full window to show it This means that if you have a rectangular grid Magmap will stretch ot shrink a certain coordinate axis so that it is all visible E g in the case of a grid that is 100 x 1000 Magmap will graph the X axis from 0 to 100 and will graph the Y axis from 0 to 1000 In order to make it all visible Magmap might display one inch per 10 meters in the X direction and one inch per 100 meters in the Y direction If you want the scaling of X and Y to be the same you can select the option Use true map coordinates In this case our original grid that was 30 x 100 would appear like the grid below 7 _100_bin X You can use the scroll bar to get to the bottom 5 6 Using grid lines When you zooming closely in at regions of the graph grid lines will be very useful in determining positions and magnitudes These grid lines are available for both coordinate plots and time series plots 102 You can enable grid lines by choosing Grd Lines from the Scal menu By default these are not enabled It should bring up the f
57. Cancel Selecting Plot Sensors Setup will let user select the readings for a specific sensor to be plotted For the 2D 3D plot it only allows one sensor to be plotted at a time Plot All Sensors option is inactive for the same reason After selecting the new sensor and clicking on OK button it will repaint the window using readings from selected sensor However if user accesses Plot Sensors Setup from Profile Plot Mag Field Plot it allows multiple sensors selection To do this hold down the CTRL key and then click each sensor you want to select Fn Sensors Setup Sensor 2 Use Ctrl Key and Mouse ta Select Multiple Sensors Only One Sensor Allowed for 20430 Plot Cancel 5 1 3 2 SET GRID SIZE You can also set the number of gridding points used by clicking on the Set Grids option on the menu obtained by right clicking on the contour plot Plot Sensors Setup Plot all Set Min and Max Field Set Grids 20 30 Plot Only This should then bring up the following dialog box Set Grids of Grid Points x Width 0 747475 100 Y Width 1 0101 100 Cancel In this case 100 grid points are used to define X and Y This is the default The X and Y width are calculated by taking the total X and Y distance respectively and dividing by the number of grid points desired Hence if you want to have a different width the number of grid points will change acco
58. D 7 897378 0 03377 604845 Y 8 006 0 041 7 897 77v 7252782 81 Mew coordinates are Longitude and Latitude At the beginning this dialog box will be blank To add points interactively press the Add point button and fill in fields in the New Reference Point dialog New Reference Point X Global coordinates e 554981 7253889 Local mapped coordinates A 00 E Cancel In the Global section type geographical State plane UTM etc coordinates in the first two fields Type the local X Y coordinates below in the Local dialog box Press Ok As soon as four of more points are added the program computes a solution Solution coefficients are displayed in the dialog box shown on previous page along with computed errors DX DY 84 and Distance Note that point 1 in the dialog box has a Distance mismatch of 21 86 m Clearly this point will cause an incorrect repositioning of other points and should be removed from the computation Points in the list can be deleted or modified by selecting the appropriate strings and pressing Delete or Edit buttons The program treats the entered positions in differing manners depending on whether the New coordinates are Longitude and Latitude box is checked or not If this box 1s left unchecked the values DX DY Distance are computed as simple Cartesian distances between points in whatever units feet or meters the
59. D DIRECTION to the first item line going up in the increasing Y direction Every sutvey line going in that direction will have the gradient computed as the following left right Every survey line going in the opposite direction will have the gradient computed as the following right left 12 1 1 5 VERTICAL GRADIENT TOP BOTTOM You had two sensors one on top of the other You want the vertical gradient with the bottom sensor magnetic field subtracted from the top sensor magnetic field 12 1 1 6 VERTICAL GRADIENT BOTTOM TOP You had two sensors one on top of the other You want the vertical gradient with the top sensor magnetic field subtracted from the bottom sensor magnetic field 12 1 1 7 LONGITUDINAL GRADIENT REAR FRONT WHEN WALKING ACCORDING TO FORWARD DIRECTION You had two sensors second sensor in front of the first sensor 169 You want the longitudinal gradient with the front sensor magnetic field subtracted from the rear sensor magnetic field when you walked according to the picture defined in FORWARD DIRECTION For example if you set the FORWARD DIRECTION to the first item line going up in the increasing Y direction Every survey line going in that direction will have the gradient computed as the following rear front Every survey line going in the opposite direction will have the gradient computed as the following front rear 12 1 1 8 LONGITUDINAL GRADIENT FRONT
60. E L ain ee es ee Se Meee eee eee LILLLLIBLLL Hb LEE D 9 SEE mami EMI Eee ee a p 18 PRLS Ee URS S mi mium PERE ED EB Cee L di L H GPS file E BBUT est with dr est with dropouts txt 880 file with one sensor plotted 16 3 Basic editing operations for 880 Data As seen from the above 880 file there are several dropouts and it will be difficult to look at the data while the dropouts remain This section will discuss basic filtering techniques to remove the dropouts and display the data in a reasonable fashion 183 16 3 1 Rescaling the data We would first like to re scale the data so that we can see the source and extent of the dropouts We can re scale by clicking on the right mouse button This will bring up the following pop up Plot Sensors Setup Plot All Sensors Set Min and Max Field Set lange AU Plot irl menu From here we should select Set Min and Max Field The following dialog box will then come up Set Vertical Scaling Maximum field 0021 904 Minimum theld 49900 Restore Default C
61. E HOW TO PLOT A STACK PROFILE SCALING A STACKED PROFILE HOW TO TURN AUTO SCALING OFF BASIC SCALING OPERATIONS TRUE MAP COORDINATES USING GRID LINES MARKING ANOMALIES FOR FURTHER STUDY SETTING A FLAG REMOVING A FLAG LOCATING A POSITION BASE STATION AND SURVEY READINGS MAGMAP S USE OF BASE STATION DATA SETTING DIURNAL PARAMETERS BASE STATION ONLY ADDING A BIAS TO DIURNAL MAGNETIC VALUES ADDING A BIAS TO DIURNAL CLOCK VALUES PERFORMING DIURNAL CORRECTION DESPIKING BASE STATION DATA SMOOTHING BASE STATION DATA WITH A SPLINE FILTER BASE STATION USER INTERFACE DESCRIPTION AND SYMBOLS DEFINITION115 SETTING PLOTTING PARAMETERS BASE STATION FILE FORMATS PROCESSING MAGNETIC FIELD READINGS INTRODUCTION A TYPICAL DESPIKING SESSION REMOVING DROP OUTS REMOVING SPIKES DESTRIPING INTRODUCTION USE OF THE DESTRIPING DATA WIZARD RESULTS OF DESTRIPING PSEUDO GRADIENT GPS OVERVIEW LOADING YOUR GPS DATA ENABLING DISABLING UTM COORDINATES 102 107 108 110 110 111 111 112 112 113 113 113 113 116 117 118 118 118 119 120 121 121 121 127 130 133 133 133 135 8 4 8 5 8 5 1 8 5 2 8 5 3 8 6 1 8 6 2 8 6 3 e 9 1 9 1 9 2 11 1 11 2 LET V2 112 5 11 2 4 T 1 2 5 12 12 1 12 1 1 12 12 12 353 12 1 4 12 1 5 12 1 6 12 1 7 12 1 8 12 1 9 12 2 12 2 1 1222 13 GPS OFFSET SMOOTHING POSITIONS RECOMMENDED SMOOTHING P
62. E 174E 30 003W 006W 000E 60 177E 174E 180W Obtained from Software Documentation for GCTP General Cartographic Transformation Package National Mapping Program Technical Instructions U S Geological Survey National Mapping Division Oct 1990 e Scale factor Input 9996 for UTM coordinates e Northing Easting These are constant values that you would like to add to your UTM coordinates UTM coordinates are usually large numbers on the order of a million meters but your survey may only be looking at thousands of meters This allows you to simplify your final numbers by adding or subtracting a large offset Occasionally you may see a warning such as the one below when you enter the UTM setup screen 96 A Distance between central meridian and average longtitude of your data mare then degrees Unless you know exactly what you are doing please use autoset of UTM parameters or da nat use UTM at all Answer OK IF you want autoset In most cases it is a good idea to have the program automatically set the UTM parameters since a bad value for the prime meridian can seriously affect how your data appears on the screen 137 8 4 GPS Offset This feature is available for surveys where you earlier selected Draw new map using GPS data and the features of an airborne survey 1t allows you to specify one or more offsets in relation to the GPS that you want to be calculated and exported This is needed when you hav
63. G UP A GROUP OF POSITIONS ALONG A SLOPE For example suppose that the back edge of the map plotted in Figure 42 should be sloped in the following manner e Top left corner of the map is at 0 Y 600 e Top right corner of the map is at X 45 Y 650 First select all the positions at X 600 as shown in Figure 53 72 nnnnnnnnnrn m m m m m m mg NM NM NM IE p gm m m I 9 m m m m I 9 m m m m IE p m m m Figure 53 Click the right mouse button and select Line Up Selected Positions Along A Slope from the pop up menu The dialog box as shown in Figure 54 should now appear on the screen Intersect Selected Position s With Line Defined By 2 Points Figure 54 Type the coordinate of the top left corner of the map in the point 1 coordinates field Type the coordinate of the top right corner of the map in the point 2 coordinates field Then left click the mouse on the OK button You should now get the right shape of the map as shown below in Figure 55 mmm m n p y m m m m m y m m m m m NM y E m gm m m y m m m m m y m m m m m NM BEN ES PSI PLI PH Figure 55 4 5 2 4 SHIFTING A GROUP OF SEGMENTS CONTINUOUS SURVEY MODE ONLY You can shift a group of segments the same way as a single segment see paragraph 4 4 1 Shifting a segment page 62 4 5 2 5 REVERSING A GROUP OF SEGMENTS CONTINUOUS SURVEY MODE ONLY You can reverse a group of seg
64. L key and selecting objects with your left mouse button e Export MagPick profile This will export a profile that you can use with the MagPick program 12 2 2 Output Files There are a few different file types you can export 12 2 2 1 SURPER This outputs a file in Surfer format You can select any combination of fields to export and this will export them with headings in a format compatible with Surfer A typical Surfer file is shown below magnetometer_X magnetometer_Y GPS X GPS Y 3 855 1 122 1852905 37 4305114 122 1852782 37 4305008 50L99 0 7600 122 1852912 37 4305121 122 1852790 37 4305015 50096 44800 122 1852920 37 4305129 122 1852798 37 4305022 49944 51800 Here we chose five fields to output two position pairs that we specified and the first field reading 29 Note Surfer will only read data files with the extension dat slk csv or txt 173 12 2 2 2 GBOSOPFT This outputs a file in Geosoft format A Geosoft Analysis and Plotting Software file has the extension xyz and it has headings and a separate line that lists the line number A typical Geosoft file is shown below magl X magl Y mag2 X mag2 Y G 858_1 LINE 0 122 1849910 37 4302225 122 1849192 37 4301530 50199 07600 122 1849918 37 4302233 122 1849200 37 4301537 50096 44800 122 1849926 37 4302240 122 1849208 37 4301544 49944 51800 122 1849933 37 4302247 122 1849215 37 4301552 49810 18600 Here the
65. LINE UP POSITIONS ALONG A SLOPE 20 2 4 HOW TO UNDO THE PREVIOUS OPERATION 20 2 5 HOW TO VIEW A PROFILE OF THE READINGS 30 2 6 HOW TO CREATE A 2D CONTOUR MAP OF THE READINGS 30 2 7 HOW TO CREATE A 3D MAP 30 2 8 HOW TO PLOT STACK PROFILES ON THE MAP 30 2 9 HOW TO FILTER THE READINGS 31 2 10 HOW TO EXPORT YOUR SURVEY TO SURFER OR GEOSOFT 31 3 IMPORTING A SURVEY 32 3 1 DOWNLOADING A SURVEY FROM A G 856 OR G 858 MAGNETOMETER 32 3 1 1 SELECT IMPORT FROM THE MENU 32 341 2 SETTING THE G 858 MAGNETOMETER FOR UPLOAD 32 3 1 3 SETTING THE PC FOR DOWNLOADING 32 3 2 OPENING A SURVEY FILE 35 3 2 1 OPENING A FILE USING THE MENU OR THE TOOL BAR 36 32 2 OPENING A FILE USING DRAG amp DROP WINDOWS EXPLORER 37 3 3 SETTING THE TYPE OF SURVEY 37 3 321 G 858 COMPRESSED FILES 38 3 29 25 OPENING A G 858 SURVEY ASCII FILE 38 16 2 929 3 3 4 222 3 3 6 en 3 3 8 3 3 9 3 3 10 3 3 11 So M S 3 4 3 5 gt 4 1 4 2 1 A DD 2 2 9 4 3 4 3 4 3 2 4 3 3 4 3 4 4 3 5 4 3 6 4 4 1 4 4 2 4 4 3 4 4 4 4 4 5 4 4 6 4 5 1 4 5 2 4 6 4 6 1 4 6 2 4 6 3 4 6 4 4 6 5 4 6 6 4 7 n 5 1 OPENING A G 856 SURVEY ASCII FILE 39 OPENING A MAGLOG PROJECT FILE 39 OPENING AN INDIVIDUAL MAGLOG FILE 40 OPENING A G 856 MAGMAP FOR DOS FILE 40 OPENING A MAGSEA PROJECT 40 OPENING A MAGSEA INDIVIDUAL FILE 40 OPENING A MGS FILE MARINE GRADIOMETER SOFTWARE 40 OPENING A G 858 BIN FILE AND CORRESPONDI
66. NG CSV FILE 40 OPENING SURFER DAT FILE 40 SHOWING ALL FILES 46 DEFINING THE GRID G 858 SIMPLE SURVEY MODE OR G 856 ONLY 46 CONCLUSION 47 EDITING OF THE MAP 49 MAP USER INTERFACE DESCRIPTION AND DEFINITIONS 49 SELECTING AND EDITING A SINGLE POSITION 52 MOVING A POSITION TO A NEW LOCATION 52 SHIFTING A POSITION 54 DELETING A POSITION 54 SELECTING AND EDITING ENTIRE LINES 55 SHIFTING A LINE 56 REVERSING A LINE 56 CORRECTING A WALKING DEVIATION 57 ROTATING A LINE 59 MOVING THE END OR START OF LINE POSITION 59 DELETING A LINE 60 SELECTING AND EDITING SEGMENTS CONTINUOUS SURVEY MODE ONLY 60 SHIFTING A SEGMENT 62 REVERSING A SEGMENT 62 CORRECTING A WALKING DEVIATION 63 ROTATING A SEGMENT 65 PLOTTING MAGNETIC FIELD READINGS OF THE ENTIRE SEGMENT 65 DELETING A SEGMENT 66 SELECTING AND EDITING A GROUPS OF POSITIONS 67 SELECTING A GROUP OF POSITIONS 67 EDITING A GROUP OF POSITIONS 69 SELECTING AND EDITING THE SURVEY GRID 74 SHIFTING A GRID 75 REVERSING A GRID 76 ROTATING A GRID 77 GRID SETTINGS 78 EXPORTING THE SURVEY TO GEOSOFT OR SURFER 78 PLOTTING MAGNETIC FIELD READINGS OF THE ENTIRE SURVEY 78 MAGMAP2000 COORDINATE TRANSFORMATIONS 79 OTHER VIEWS OF READINGS 88 2D CONTOUR AND 3D SURFACE PLOTS FOR MAGNETIC FIELD READINGS 88 18 CREATING A 2D OR 3D PLOT EQUALIZING COLORS TECHNIQUE FOR CONTOUR PLOT PLOT OPTIONS FOR 2D 3D PLOT USER INTERACTIONS FOR 2D 3D PLOT SHADED RELIEF PLOT STACK PROFILE PLOT WHAT IS A STACK PROFIL
67. Other utilities 11 1 BintoAsc utility G 858 files have a binary format and therefore it is impossible for the user to modify them However sometimes it is necessary to access the data directly this might be due to a hardware problem or if the user wants to do data manipulation outside of Magmap The Bzuto ASC utility allows the user to convert the binary data file to an ASCII file and save it Note If the user uses Magmap to save ASCII data often data like GPS data or serial data logged onto the console will not be saved in the same file To use this feature go to the Fz menu and select Binary 858 gt ASCIL You should see the following dialog 3 B58 binary to ASCII conversion Files Input file E Program Files M agmapdb dataset bin Browser Output File C Program Files apJ6 dataset stn Browser Outputreadings I Output discontinuities I Output marks IY Output pauses I Output field notes Output serial data W Output unpauses Cancel Here you can select the input and output file names Additionally you can select if you want to output all your data or output specific types of readings When you press the program will run a conversion routine and create your output file You are free to load this file into Magmap or use it for other purposes Please see the G 858 manual for the description of the formats of the above types of entries 157 11 2 GPS Interpolator 11
68. PLE MANIPULATING A SURVEY WITH A CSV FILE LOAD THE FILES LOOKING AT THE GPS DATA DRAWING IT AS AN 858 MAPPED SURVEY DRAWING THE DATA USING THE FEATURES OF A MAGLOG SURVEY SAMPLE ANALYSIS FROM A MAGLOG FILE LAYOUT OF SURVEY IMPORTING THE FILES BASIC EDITING OPERATIONS FOR 880 DATA RESCALING THE DATA PLOTTING SECOND SENSOR DESPIKING THE DATA MANIPULATING THE GPS FILE USING UTM COORDINATES SMOOTHING GPS DATA OTHER OPERATIONS SETTING OFFSETS EXPORTING TO A FILE 178 178 179 179 181 182 182 182 183 184 185 187 189 190 193 195 195 196 ANALYZING AN 858 LAND SURVEY WITH GPS POSITIONS SURVEY LAYOUT FILE FEATURES ANALYSIS OF MAGNETOMETER FILES LOADING THE FILE MANIPULATING THE MAP DRAWING THE GPS MAP EDITING THE GPS DATA EDITING MAGNETOMETER DATA THAT GOES WITH THE GPS THE BASE STATION FILE EXPORTING THE DATA FURTHER DATA MANIPULATION PROCESSING THE SECOND FILE CONCATENATING TWO FILES ANALYSIS IN SURFER G 858 SURVEY WITH NO GPS DATA LOADING THE FILE MANIPULATING THE MAP SAVING CURRENT WORK 19 198 198 199 199 200 200 201 207 208 210 213 213 213 214 216 216 217 221 18 2 18 3 18 4 18 4 1 18 4 2 18 5 18 6 18 7 18 7 1 18 7 2 18 7 3 MANIPULATING THE G 858 DATA THE BASE STATION DATA ANALYSIS OF G 858 DATA FROM WITHIN MAGMAP SETTING A PROPER SCALE USING THE STACK PROFILE EXPORTING THE DATA FURTHER DATA MANIPULATION ANALYSIS IN SURFER USING
69. ROCEDURE WARNINGS ABOUT SMOOTHING REFERENCES ON SPLINES TROUBLESHOOTING MAP APPEARS INCORRECT WHEN USING GEOGRAPHICAL COORDINATES 147 MAP APPEARS INCORRECT WHEN USING UTM COORDINATES CANNOT GET ORIGIN OF GRID TO CORRESPOND TO 0 0 OTHER DEVICES METAL MAPPER OPENING A METAL MAPPER DATA FILE TREATMENT OF METAL MAPPER DATA 138 140 145 145 146 147 147 147 148 148 148 148 USING MULTI TELEGRAM MESSAGES WITH MAGMAP2000 EXAMPLE USING GPS VTG MESSAGES OTHER UTILITIES BINTOASC UTILITY GPS INTERPOLATOR INTRODUCTION SELECT INPUT AND OUTPUT FILES INTERPOLATING OTHER DATA SETS SELECT UTM TRANSFORMATION PARAMETERS RUN INTERPOLATION EXPORTING TO GEOSOFT OR SURFER EXPORTING A LAND BASED SURVEY SETTING THE TYPE OF SURVEY SETTING BIAS FOR MAGNETICS SETTING THE SENSOR SEPARATION FILE FORMAT OUTPUT FORMAT OUTPUT FILE EXPORT NOW CANCEL SAVE SETTINGS BASE STATION SURVEY BOUNDARY CONSIDERATION EXPORTING A MAGLOG NT SURVEY EXPORT PROCEDURE OUTPUT FILES SAVING YOUR EDITING 150 150 157 157 158 158 159 162 164 165 167 167 168 170 170 171 171 171 171 172 172 172 172 173 176 15 1 15 2 15 2 1 15 2 2 16 1 16 2 16 3 16 3 1 16 3 2 16 3 3 16 4 16 4 1 16 4 2 16 5 16 5 1 16 5 2 17 1 17 2 17 5 17 3 1 17 3 2 17 3 3 17 3 4 17 3 5 17 3 6 17 4 17 5 17 5 1 17 5 2 17 6 18 1 1 18 1 2 18 1 3 20 PRINTING 177 EXAM
70. UTM Setup menu and fill in the offsets as follows UTH transformation setup v Enable UTM transformation parameters Ellipsoid name 5 84 1394 Major axis meters Flattering UTM projection parameters Autoset projection parameters Central meridian degrees 51 Scale factor 0 9666 for 0 9996 Northing meters 4387 412 11 Easting meters 421 233 8 191 Cancel Note Here we select the values for Northing and Easting by taking the negative of the two coordinates numbers in the bottom left corner of the GPS graph See graph When we press OK we get the following GPSTesttxt m BL E ILU LL Hub TT Ltt Lo ULL Ub Lb DL Se Him Hg ee mom um HH EHI LLL Wt utc p S NH I n NEININEE aur gb DIT GREE m auum LLL U UL mum 8 ee HO ee oe ee ITT Tt Tit zB E i ii m mu E F Note that the bottom left corner now corresponds to 0 0 If you export data it will also be in this coordinate system with the offsets you selected 192 16 4 2 Smoothing GPS Data We would now like
71. User Guide GEOMETRICS INC Magmap 2000 User Guide 24891 01 Rev H 2000 24890 01 2000 Magmap 2000 4 0 User Guide Geometrics Inc 2190 Fortune Dr San Jose CA 95131 Phone 408 954 0522 Fax 408 954 0902 Sales geometrics com NEW MAGMAP 2000 FEATURES 25 Oct 2002 Manual Addendum There are several exciting new features in the October 2002 release of MagMap 2000 We list them here as a manual addendum and as a PDF for website distribution I The Problem In the contour map generation routine the Legend was always visible and if you made the map with many contour interval colors the legend became bigger than the map The Solution Now by right clicking on the map you can select Plot Color Legend box or not If you turn it off then you can get a larger picture of the map on the screen for zooming and further analysis Remember that when in PLOT DATA display profile display you can select anomalies for flagging by right clicking on the profile and selecting SET FLAG When you do that the flag appears on the profile number 1 below on the position map and also on the color contour map showing the position of the anomaly Put the cursor on the anomaly and read the X Y or Latitude Longitude of the cursor on the info bar at the bottom Plotting Mag Field in 2D Contours for Sensor 1 57 4316 37 4515 57 4314 37 4313 37 4312 57 4311 37 4310 37 4309 357 4308
72. X and Y offset For example in the survey plotted in Figure 10 if you shift the grid by X 5 and Y 100 you will obtain the picture in Figure 58 m m my m mg gm M M Im NEN p m m mW m m m M m m mW E 1 63 Figure 58 4 6 2 Reversing a grid There are several options for reversing a grid To reverse every line of the survey select Reverse Every Line and Reverse In Both Directions To reverse every even line of the survey select Reverse Every Even Line and Reverse In Both Directions Every other line starting with the first line acquired in the survey will be reversed To reverse every odd line of the survey select Reverse Every Odd Line and Reverse In Both Directions Every other line starting with the second line acquired in the survey will be reversed Figure 59 For example in the survey plotted in Figure 10 if you reverse every line in both directions you will obtain the picture in Figure 60 76 LET EL ELE a EU 4 y 4 y 4 y 4 y 4 y Figure 60 4 6 3 Rotating a grid Figure 61 Type in the rotation field the angle of the rotation in degrees from 360 to 360 degree Type in the X and Y field the coordinates of the rotation origin Once you enter all the fields click the left mouse button on the button or press the ENTER key For example in the survey plotted in Figure 10 if you
73. a dragging algorithm to calculate positions or not e X This is the horizontal offset in meters see diagram in GPS Offset Setup of your position from your GPS Assume the GPS is at the coordinates 0 0 Then from here you 139 need to specify how far right positive X or left negative X your position is from the GPS Assume that you ate facing in your direction of travel e Y This is the offset in meters parallel to the direction of travel of your position from the GPS If your position is in front of the GPS this will be represented by a positive Y If it is located behind the GPS this offset should be negative e Z This is the vertical offset in meters of your position from the GPS If the GPS is above the position point you would like Magmap to calculate this offset should be negative If it is below the point you would like to calculate this offset should be positive Note GPS of vertical positions are typically two or three times less accurate than X Y accuracies e Name This is an identifier by which this position will be known When you ate exporting you can choose to export the position by selecting this name Additionally this name will be printed in the heading of the export file should you choose to export the position e Use Dragging This is used for marine surveys to give better position calculations If you check this and select a positive dragging distance in meters Magmap will calculate the
74. above we can get a dramatically different picture such as the one shown below 180 sampcsv bin it li Ar ep ro tT dag SS Ani l I is M muli rer oen EET Lt I DNE PT Mitty ea Se ES T a m SUD Tm FE l i al 14444441141 1144444444 Yen ng iu x ib gt aiiis mt b gsm E TT ry 1 illi MT m pupa ELER Em EE _ er liddige E 11 1 3l qn li pas E j l Li Map plotted using incorrect GPS time corrections 15 2 2 Drawing the data using the features of a Maglog survey This survey type allows us to add offsets later if needed The main difference between the two is that you will get three views one of your GPS positions graphed on top of your marks and lines that you set one of your magnetometer data and one of the survey grid you set up From here you can despike your data and do your normal GPS smoothing operations 181 16 Sample Analysis from a Maglog File This section discusses how to analyze data from Maglog NT files It specifically covers operations that you might need to do such as calculating additional magnetometer position points smoothing GPS data and
75. al to UTM coordinates This can be done from within the menu option UTM Setup You should see the following dialog box that will allow you to set specific parameters related to your sutvey UTH transformation setup Fa Ellipsoid parameters Ellipsoid name WGS 84 1384 Major axis meters Flattening 299 254 UTM projection parameters Autoset projection parameters Central meridian degrees 105 Scale factor 0 9666 far jo 3996 Northing meters Easting meters Cancel e Enable UTM Transformation This allows you to turn the UTM transformation on and off When it is off Magmap will use geographical coordinates Magmap will use the given parameters to calculate UTM parameters when it is checked e Ellipsoid name This is the type of ellipsoid you use to approximate the earth Since the earth is not a perfect sphere some ellipses may better approximate the region you are surveying than others e Autoset projection parameters This is useful when you don t know what the prime meridian you are using is or when you data where your prime meridian may change This will set the prime meridian and scale factor automatically for you e Prime Meridian If you don t press Autoset projection parameters you should fill this in This value has a large impact on the UTM coordinates generated due to the non uniformity of an ellipse It can be quickly e
76. alog box Here we have chosen to export a number of fields magnetometer de 1 60 dy 0 00 magnetometer r de 1 60 dy 0 00 GPS de 0 00 dy 0 00 d D 00 dy 0 00 QUAL_IND DOP TIME ATE E imm a 3 588 4 DIURNAL 3 DIURNAL 4 e magnetomer_X magnetometer Y the two magnetometer shifted positions we specified e GpS X GPS Y the non shifted GPS positions we specified e QUAL IND DOP two quality factors included in the GPS data e Time e 5 858 3 the first sensor reading uncorrected e DIURNAL 3 the diurnally corrected first sensor reading Base Station Reading is subtracted from sensor reading Note We have not selected G 858 4 and DIRURNAL 4 because we only had valid data on one sensor 211 We also need to make sure that we pick a suitable name for our output file and uncheck Export Data Separately to Default File Names When we are finished we press Export Now and the data is exported Some sample data from the output file appears below magnetometer_X magnetometer_Y GPS_X GPS_Y QUAL_IND DOP G 858 3 DIURNAL TIME 67 48 1 17 68 57 0 01 2 00 1 00 50199 07600 469 64900 11 26 36 900 67 41 1 26 68 50 0 09 2 00 1 00 50096 44800 367 06300 11 26 37 000 67 34 1 34 68 43 0 16 2 00 1 00 49944 51800 215 13900 11 26 37 100 67 27 1 42 68 35 0 24 2 00 1 00 49810 18600 80 81000 11 26 37 200 67 20 1 50 68 28 0 31 2 00 1 00 49719 18700 10 18600 11 26 37
77. ancel By default the minimum field 1s set to the minimum reading received in the survey Since the survey has dropouts the minimum field will be set to 0 In this case we need to change it to 49900 or some other value that will allow us to see the data so that we can see some features besides the dropouts If we press our G 880 screen changes to reflect the scale change 184 im 830T est with dropouts txt 880 screen after scale change 16 3 2 Plotting second sensor By default only one sensor is plotted Since we are interested in looking at the data from both sensors we will need to plot this as well We can plot this by right clicking on the mouse while the magnetometer window is active We will get the same pop up menu that we saw before Plot Sensors Setup Plot All Sensors Set Min and Max Field Set lange This time we need to select Plot Sensors Setup This should yield the following window 185 Plot Sensors Setup ANALOG DEVICE 1 ANALOG DEVICE Z blue ANALOG DEVICE 3 green DEVICE 4 pink DEVICE 5 vellem ANALOG DEVICE 6 white ANALOG DEVICE 7 dark blue ANALOG DEVICE amp dark green ANALOG ANALOG red Use Ctrl Rey and Mouse to Select Multiple Sensors Only One Sensor Allowed for zZDb 3D Plot cance mS mm on In this example we choose the options Analog Device 1 and Analog Device 5 because w
78. and anomaly 3 3 drums were spread out and buried shallowly about 1 8 meters In the lower left hand dipole 2 two drums were buried at right angles at about 2 0 meters depth One can see the slight differences in the shape of the dipoles 231 The drums are buried in the same orientation in the upper right hand dipole 1 but they are deeper You can see that the anomaly appears weaker and harder to see Additionally since the magnetic field is induced one can see that the dipoles point in a north south direction The drums themselves point along the Y axis of the plot but the induced dipole points in the direction of the magnetic field We can also see examples of magnetic monopoles here Example of magnetic monopole This one is from a drum buried vertically the top of it about 2 0 meters from the depth Other monopoles are characterized by an object s long axis being perpendicular to the direction of the magnetic field In this case the magnetic field was equatorial horizontal to the ground and the long axis was vertical Note the converse relation a dipole is seen when the long axis is parallel to the magnetic field as in the case of long sheets of metal being buried parallel to the ground or drums being buried parallel to the ground As you can see we can start to make guesses about the orientation and depth of things from a basic understanding of the contour plot There is a more in depth discussion on estimat
79. and Staton in G 856 is represented by a blue square Figure 10 GPS positions also show as Blue Squares Duplicate positions are positions acquired at the same location same X and Y coordinates with a different mark or line number You get duplicate positions when you sutvey the same line or segment twice or when you shift a line or segment on top of another line or segment They are represented by a double inlaid square A selected position is represented by a white square A segment is represented by an arrow that also indicates the direction the user was walking between two positions Figure 10 A grid is represented by a white dotted rectangle Figure 10 Gridlines can be configured using the Scale menu Every magnetic reading is represented by a black point Figure 10 If there are many readings between two positions it will look like a black line drawn between the two positions By zooming in every reading will be represented by a single point When the mouse cursor is placed on top of a position the status bar will indicate information about the position such as time mark line X and Y location The scaling tool bar contains 9 buttons e Zoom zoom in the map in the X and Y directions with the same zoom factor Zoom out zoom out the map in the X and Y directions with the same zoom factor e Zoom in X zoom in the map in the X direction only The scale in the Y direction remains unchanged e
80. and no output for them when exporting The difference between Linearly Interpolate Drop Outs and Remove Drop Outs is Linearly Interpolate Drop Outs will interpolate those zero readings by good adjacent readings In other words those zero readings and adjacent one reading replaced by interpolated values Therefore those readings will still be plotted or exported by the new values after filtering Remove Drop Outs is usually the preferred method because most gridding programs simply grid over the missing data Please note that Linear Interpolate Drop Outs cannot be run if Remove Drop Outs has been run first because there is no meaning to do so 119 7 4 Removing spikes Magmap allows the user to define the maximum number of readings allowed in a spike and the height of the spike We can despike the data by selecting the Filter menu Despike Linearly Interpalate Drop Outs Remove Drop Outs Despike Setup Clicking Despike Setup will display the following dialog box Setup Feak Threshold 5000 Maximum Spike Readings This allows the user to enter peak threshold and select maximum number of readings width of an anomaly in other words which could be considered to represent a spike When done clicking on the Apply button will automatically find those spikes that match the criteria and filter them out If the reading window
81. are not available for a GPS map You may move a presumably bad GPS position to a new location You also can delete bad GPS positions delete readings and plot readings Note Version 7 of Surfer for Windows now offers double precision numbers This allows nine to fourteen digit decimal 133 degrees to be faithfully represented in the Surfer map grid annotation in previous versions you need to use UTM coordinates to get accurate positioning Magmap2000 of x File Edit View Scale Fiter Gps Survey Setup Window Help cB amp IMPORT OPEN SAVE PRINT REOLIT HELP survey bin 2 7 T vemm 0 in ao cat For Help press F1 x 85 36524920 38 823817 4 Figure 68 There are small differences in the way the program will behave depending upon with which option you choose to plot the GPS window You should choose the first option Draw new map using GPS and the features of a regular 558 survey if you don t need to specify additional offset antenna to sensor position points to be calculated It also has an export menu that is simpler to use The second option Draw new map using GPS and the features of an airborne survey will allow you to specify extra positions relative to the GPS antenna to be calculated Calculating additional positions will be discussed later in this chapter 134 8 3 Enabling Disabling UTM Coordinates Magmap has the facility to do a transformation from geographic
82. be corrected by collecting repeated magnetic field measurements at a fixed sensor location and orientation over the time span of a survey The base station is placed close enough to the survey area so that the variation in field with respect to distance is assumed negligible Less then a few miles is good During analysis we can then remove these short term variations in field by subtracting time correlated base station readings from the magnetometer readings Due to the potential for high gradients and significant variation in the magnetic field during magnetic storms surveys are usually not conducted at these times Year 2000 is an eleven year solar sunspot maximum This section describes the MagMap2000 procedure for making diurnal and micropulsation corrections to data collected with the Geometrics G 858 or G 856AX magnetometers with either of the same magnetometers set up as the base station all combinations are acceptable The plotting of readings for a segment line or grid is similar to the plotting of base station readings Therefore only the base station case will be described in the following paragraphs 6 1 MagMap s use of base station data In order to do diurnal corrections MagMap needs a series of base station readings with clearly marked time stamps that correspond with the roving magnetometer data From these readings MagMap will determine which readings it can use In the best case the base station takes readings a
83. bi directional parallel lines these errors can be very noticeable and significant Heading errors can be created by any number of sources but the primary sources are heading error of the sensing system itself often in the to 2 nT range offsets due to carrying some ferromagnetic object on the operator or from the logging console or some other sensor device such as a GPS receiver or antenna being too close to the sensor Only since the advent of very high sensitivity optically pumped Cesium vapor magnetometers have these errors been visible and the necessity to remove them become apparent Heading errors are traditionally removed by using a technique that attempts to find constant magnetic offsets for each line traveled Since the causes of heading errors are usually magnetic objects that change orientation as the user changes orientation in cases of heading error there should be a constant magnetic field offset added to or subtracted from the magnetic field for each direction of the user Thus we attempt to find a technique that removes this constant magnetic field offset from each line The line to line offset minimization uses a local min max technique that searches down every line for local minima or maxima and seeks through an iterative process to minimize this offset on a line to line basis The technique we use therefore has a minimum distortion effect on large anomalies while performing quite well in the flat areas of the field where headi
84. correctly interpret the metal mapper file the following procedure should be used when opening a file 1 Download data from the G 858 console as it is described for the magnetometer However check the button Download only decompress later The result will be a binary file on your hard disk 2 Go to Open on the file menu Select Metal mapper binary files in the dialog box If you do not do it Magmap will assume that your file is a magnetometer file 3 Load the file as usual Note that the menu item Metal mapper under Survey setup is available Like the magnetometer the metal mapper has two sensors but it does not have a pseudo gradient As soon as you have worked once with metal mapper files binary files that are in your history list are treated as metal mapper files This changes after you work with the magnetometer again 9 1 2 Treatment of Metal mapper data The recommended treatment of Metal mapper data is as follows 1 For each line calculate the median value for each sensor and subtract this from the data 2 Create a set of new readings by summing the absolute values of both metal mapper channels These new values will replace the readings for sensor one and the readings for sensor two will be equal to 0 3 Plot or map this new synthetic field To do these transformations go to Survey setup Metal mapper The following dialog should appear on the screen 148 Hetal mapper transfo
85. ct Delete Segment This will delete the readings between the two positions 2 2 4 Selecting and editing the survey grid To select the grid click the right mouse button on the green area of the map To shift the grid by an X or Y offset select Shift Grid By To reverse the direction of every line or every other line select Reverse Grid To rotate a grid select Rotate Grid To change the mark and line spacing select Grid Setting 2 2 5 Selecting and editing a group of positions In order to move a several positions by a given amount you may select them as a group and then move them 2 2 5 1 SELECTING A GROUP OF POSITIONS To select a group of positions click the left mouse button and draw a rectangle around the positions to edit When you have finished drawing the rectangle release the left button Every position inside that rectangle will be selected white square 28 To select more positions press the control key CTRL and repeat the previous operation To select a single position press the CTRL key and click the left mouse button inside the corresponding position e If the positions were already selected they will be deselected if they were not selected they will be selected pressing the CTRL key togeles the selection e To deselect all the positions left click the mouse button anywhere 2 2 5 2 EDITING THE GROUP OF POSITIONS Once you have finished selecting the positions rig
86. ct deviate in the X direction When the following dialog box Figure 23 appears on the screen type 2 5 and click on Deviate line 0 in the X direction Figure 23 You should now have fixed your walking deviation as shown in Figure 24 Figure 24 If by mistake you start line 0 at X 2 5 instead of 0 and end up at X 0 and Y 600 First reverse the line then deviate the line in the X direction by 2 5 and reverse the line again 58 4 3 4 Rotating a line Rotate line Figure 25 Type in the rotation field the angle of the rotation in degrees from 360 to 360 degrees Type in the X and Y field the coordinates of the rotation origin Once you enter all the fields left click the mouse button on the OK button or pressed the ENTER key For example in the survey plotted in Figure 10 if you rotate LINE 0 by 180 degrees at the origin 0 and Y 0 you will obtain the picture in Figure 26 Figure 26 4 3 5 Moving the end or start of line position This is the same as moving a normal position as described in paragraph 4 2 1 Moving a position to a new location page 52 4 3 6 Deleting a line Delete line Figure 27 If the information reported by this dialog box confirms that this is the line you want to delete click on the YES button otherwise click on the NO button to abort Deleting a line will delete all the positions and magnetic field readings acquired on this l
87. culated Northing and Easting UTM coordinates e Save allows storage of UTM transformation parameters in a file e Load allows loading of UTM transformation parameters from file For more discussion on individual UTM parameters please refer to the UTM discussion in the Magmap2000 manual 11 2 5 Run Interpolation 165 166 The third panel is used to start the interpolation process using parameters set on the first two panels Hun interpolation Start initiates the interpolation process When the process is finished GPS Interpolator remains running and ready for additional work Stop interrupts a running interpolation Samples read the number of input data records Interpolated the number of interpolated output data records Ratio ratio of Interpolated to Samples read Ratio should be close to 100 with a good data set Finish starts an interpolation process and closes GPS Interpolator when the process is finished 12 Exporting to Geosoft or Surfer Before you export you should be aware of which type of survey you are dealing with This is important because different options are available for different types of surveys and the export menus and procedures appear quite different Each of the following sections will define the type of surveys that are supported 12 1 Exporting a land based survey This export procedure covers the export menu that you will see for land based surveys
88. d square Then select Plot Mag Field in 3D Surface 2 8 How to plot stack profiles on the map This is only applicable for land based surveys such as G 858 or G 856 Position the cursor on one of the lines of the map and press your right mouse button Select Plot Stack Profile on lop of Then select Plot Sensors Setup and choose which sensor you want to plot You should then see a series of profiles appear over your lines Plus Minus Keys control the amplitude of the stacked profiles 30 You can zoom in and out by using the zoom buttons a toolbar located at the top of your screen If they are grayed out make sure that you have disabled AAvays Fat in Window from the Scale Menu 2 9 How to filter the readings Select Filter from the menu then Despike or Linearly Interpolate Drop Outs Despike will only remove spike s above 1000 nT Use despike with caution in discrete survey mode as the readings may change rapidly near an anomaly and thus the anomaly may be interpreted as bad data and filtered out 2 10 How to export your survey to Surfer or Geosoft First open or download one or more base station files if a diurnal correction is Op desired Then select File from the menu then Export or right click the mouse button on the green area of the map then select Export The diurnal correction will be done automatically if the time of any opened base station fi
89. data including re scaling offsetting and correcting for diurnal variations Finally after positioning the data Magmap will write an ASCII file suitable for input to a 3D surface plotting program such as Surfer for Windows or Geosoft Analysis and Plotting Software Such files consist of x and y coordinates field values difference between values in the case of gradiometer data and time and date for each magnetometer reading These files are typically about 3 MB per hour of data collected After data corrections are applied the corrected raw data may be stored in ASCII format with an STN extension This will be necessary if you have not completed all the editing you wish to do and wish to continue at a later time 1 2 Requirements The G 656 can collect an enormous amount of data Marine Mags create even larger files Even modest size surveys will require large computer resources in terms of RAM and hard disk space You will need a minimum of 16 MB of RAM 24 installed on your computer Plenty of hard disk space will be necessary as well if you want to store lots of data Typical Windows95 Windows 98 Windows NT and Windows 2000 installations will have enough resoutces Additionally some of the larger surveys will be very time consuming We recommend at least a Pentium system with 32 MB RAM although Magmap will run on slower systems This program will not run under MS Windows 3 1 It will run under Windows NT 3 51
90. difference iterations Hence a good result involves picking a small enough iteration step to not overshoot the correct value and additionally doing enough iterations 7 5 2 4 LINE SMOOTHING PARAMETERS DIALOG This dialog is used to help us smooth the data to remove high frequency noise stride noise Typically stride noise is very small on the order of 0 2nt and we do not wish to effect any actual anomaly data so we allow an upper limit on what we will consider stride noise The default for this parameter is InT We consider any anomaly of greater than InT that is coherent to be real and we do not want to remove it We recommend initially leaving this setting at InT If for instance the stride noise 1s larger due to some magnetic object on the survey personnel then this value should be increased This dialog box 1s shown below 125 Line smoothing parameters Dynamic range for smoothing nT lt Back Cancel A low pass filter is used to filter the stride noise Additionally to keep from filtering out actual anomalies we use a setting Dynamic range for smoothing This setting is used as a guideline when trying to distinguish anomalies from noise 7 5 2 5 RUN DESTRIPING DIALOG The Run Destriping dialog box gives us to options either running Destriping in a test mode or to actually apply the filters and write out the files Clicking on Run Destriping will run the program without writing out th
91. e know that we have two 880 magnetometers each with signal depth and altitude measurements The data that 1s logged will appear as the following to Magmap Thus if we wanted to graph the two signals instead we would choose to display analog channels 2 and 6 After we have pressed the magnetometer screen should look like the following 186 Field 1 Analog Channel 1 Signal 1 Analog Channel 2 Depth 1 Analog Channel 3 Altimeter 1 Analog Channel 4 Field 2 Analog Channel 5 Signal 2 Analog Channel 6 Depth 2 Analog Channel 7 Altimeter 2 Analog Channel 8 fe 880T est with dropouts_txt Scaled magnetometer data 16 3 3 Despiking the data In the above case there are spikes and drop outs in the data Magmap has facilities for removing both The generic option Lnearly Interpolate Drop outs will remove drop outs with varying numbers of points involved It will replace the drop outs points with valid points nearby This doesn t involve much conscious effort on behalf of the user If we select this option through the despike menu we will get the following im S80T est with dropouts_txt Scaled magnetometer data with dropouts linearly interpolated 187 In this case the drop outs have been removed However there are still spikes that need to be removed The readings that are left after removing drop outs are not zero readings but they still are significantly different from n
92. e Offsets setup 140 Northing 138 192 193 offset 27 28 29 52 54 55 56 61 62 70 75 76 89 113 138 139 140 141 148 201 203 206 220 Opening a file 35 Output file 78 172 Parameter 143 Plotting readings 30 Position deleting 54 editing 27 moving 52 selecting 27 52 shifting 54 prefixed data 151 Prime Meridian 136 printing 178 psuedo gradient 131 Readings despiking 119 filtering 119 Readings plotting entire survey 78 117 parameters 117 Reversing grid 76 line 56 segment 62 Rotating grid 77 line 59 Rotation segment 65 Saving to a file 177 Scale factor 138 scaling 49 50 91 94 101 102 103 105 117 Segment Definition 60 deleting 66 deviation 63 editing 28 60 Editing 60 Operations 61 reversing 62 rotating 65 Selecting 60 shifting 62 Selecting a group 29 67 Settings grid 78 shaded relief plot 94 Shifting grid 75 line 56 segment 62 Sloping edges 30 Smoothing 142 146 194 Spl Smooth 143 splines 147 Stack profile 96 99 226 State Plane 79 sun azimuth 96 Surfer 31 78 169 Survey plotting readings 78 117 True map coordinates 50 103 117 Undo 30 Uploading 32 UTM 79 134 136 137 138 148 191 192 203 204 205 206 214 215 XYZ file 78 172 235
93. e a GPS but your magnetometers are not located at the same place as your position point was taken In the case of a handheld magnetometer G 858 survey the GPS antenna is always a fixed offset away from your magnetic sensor In the case of a matine magnetometer G 880 or G 881 the sensor is towed on a cable of fixed length In order to produce a final data set without positional errors distance offsets from the GPS antenna to the sensor must be calculated These values are then used to recalculate the actual sensor position The position points that you specify in the offset screen will only be calculated when you export your data The recalculated sensor positions can be viewed in Magmap but must be exported and read back in You can set offsets by pressing GPS Offset This should bring up the following dialog box GPS Offset Setup Ea Magnetometer offsets magnetometer 1 magi dx 0 dyz1l rage dx i 0 maga dx 0 i 0 GPS magnetometer 3 77 v magnetometer 2 a rf m tvpical for hand held typical for marine or airborne Horizontal offsets are posite ta the right af the GPS and negative to the left af it facing inthe direction af motion Parameters ta calculate direction of mation Points to look Forward 5 Points to look backward 2 Offsets Multiple offsets setup GPS clock bias secs o Cancel The picture shows the coordinate system that is being
94. e are two problems to be considered here e How do we transform local 858 coordinates into State Plane coordinates or some other coordinate system If both coordinate systems were defined completely without errors it would be sufficient to measure only two corresponding points in each system e How do we take into account possible irregularities in the 858 coordinate system such as non parallel lines curved lines or irregular mark spacing along the line In this case it is not enough to define the transform using only two points It could be that a new coordinate for every positional mark would be required Keep in mind that methods described below also can be used for direct transformation between Latitude Longitude pairs State Plane coordinates and vise versa The transform functions will typically be of most value where the survey is conducted without GPS but the final map product requires GPS positioning The process is as follows After the survey is completed the positions of the four corners of the survey area are measured with the geodetic grade GPS and coordinates are recorded as Latitude Longitude ot State Plane coordinates Alternatively the positions of all survey marks including end of line marks could be measured with the GPS Note State Plane coordinates can be easily obtained with from Lat Lon pairs using CORPSCON software program which is freely available from the Army Corps of Engineers at http crunch tec army m
95. e between Geosoft or Surfer output format 12 1 5 Output format You can individually select the output fields you want to export to Geosoft or Surfer by clicking the left mouse button on each item Outputs that are supported are e X your X coordinate or longitude Y your Y coordinate or latitude e Sensor 1 reading e Sensor 2 reading e Gradient between Sensor 1 and Sensor 2 e Dturnally corrected Sensor 1 reading Base Station Reading Sensor Reading e Dturnally corrected Sensor 2 reading Base Station Reading Sensor 2 Reading e Time Date Line and Mark all features in land based surveys done with G 858 magnetometer These outputs are only available for surveys with 2 magnetomters You need a base station file 12 1 6 Output file Type the file name of the new Geosoft Analysis and Plotting Software or Surfer file By default the file name is the same as the survey file with the extension xyz for Geosoft and dat for Surfer You can use the browse button to select another directory or drive 12 1 7 Export Now Cancel Save Settings If you are ready to export your survey click the left mouse button on the Export now button otherwise you can cancel by clicking on the Cancel button or save your export settings by clicking on the Save settings button 171 12 1 8 Base station If no base station files are currently opened a blinking warning message will remind
96. e compressed 34 format to save some space on your hard drive By default this feature is disabled Current hard drive sizes may make this unnecessary 3 1 3 6 READY TO DOWNLOAD Once you have defined all the data sets you wish to download click the left mouse button on the DOWNLOAD NOW button or Cancel to abort the download operation and close this dialog box You should see the following screen while the downloading is happening Downloading G 856 data Serial port COM2 at baud rate 175200 Dataset 2 Block 274 Connected Downloading data Cancel This screen allows you to see the status of the downloading whether a connection has been established etc You can also see the COM port selected and the baud rate For every survey you download a new DOS window will appear on the screen reporting the status of the downloading process Once your survey has been downloaded if the option Decompress later has not been set your survey file will be opened automatically Note If your downloading does not work you can have Magmap use the DOS utility binxfer exe To enable this you need to edit the Magmap ini file by going to the Windows system directory and double clicking on Magmap ini Find the string BINXFER 0 and replace it with BINXFER 1 Magmap will now use the DOS utility to download If you do not need to open the file manually you can skip the next paragraph that exp
97. e file so that the users can see the results of the parameter selection In particular we want to see the maximum offsets corrected and the average and maximum disbalance after the line to line balancing is applied If the values are still too high then you are given the option to go back to the earlier screens to select different parameters Typically we like to see less than 5 nT maximum correction and a maximum disbalance after destriping of perhaps 5 When you are happy with the results press Finish and the actual destriping process with file output will occur 126 Hun destriping E Maximum carrectian nT Maximum disbalance Average disbalance X lt Back Finish Cancel Bring the resultant file into Surfer or Geosoft and grid and display the data we recommend shaded relief for maximum contrast and dynamic range display and observe the results compared to the original dat file If the results are insufficient we recommend running the previous destriping output file through the process a second time This often generates a smoother result with the downside of removing more of the high frequency content of the data file We believe that judicious use of the spike editing and destriping routines in MagMap 2000 will afford the user powerful data correction capabilities Some experimentation will be necessary to get optimum results 7 5 3 Results of destriping Shown below is data taken and mapped withou
98. ecause some drop outs that last for a long time may not get removed if they are longer than the maximum number of points involved allowed in a spike 16 4 Manipulating the GPS file Our starting GPS file is shown below 189 GPSTest_txt 2i pl TUTTE TTT OTT MR gt E 4 TT TT mE WEL LL LU UL Ue amu ELE wi T pm Mis Hu LL 1 Lo E SE ee p HEN ENNEN eee mim HI imm EME m m masnu EL EMI TT L LLL UL E i This section will show how to change from geographical to UTM coordinates and how to smooth the data 16 4 1 Using UTM coordinates The data is originally given in geographical format However we would like to see UTM coordinates instead We can do this by selecting UTM Setup from our GPS menu We can then fill out the following UTH transformation setup W Enable UTM transformation Ellipsaid parameters Ellipsoid name 85 84 1384 Major axis meters Flattening 799 254 UTM proj
99. ect every file you wish to import by pressing the CTRL key and the left mouse button Then drag these files while pressing the left mouse button onto the MAGMAP window 3 3 Setting the type of survey The Open dialog box has a list of several types of files that can be loaded It is very important to make sure that you correctly specify the type of file that you are using You can do this by selecting the Fzs of Type option in the Open dialog box and selecting the option which fits your survey A sample is shown next Open ng AL str Ej 72 100 stn nm 70 stn Files of type G 856 Asci Files drl str Cancel MagMap will sometimes recognize the type of file that is being loaded but occasionally it will not Each option in the Open dialog box is specifically designed for a particular type of file which will be discussed below 3 3 1 G 858 Compressed files This option will allow you to open 858 compressed files If you are opening a mapped G 858 binary compressed file you do not need to enter any survey information as it has been stored with your data in the file Simple survey files require some information such as line spacing covered in Section 3 4 A dialog box indicating decompression and status information will be shown on the screen Figure 4 Decompress E Program Files MagMapS6 SAMPL Figure 4 3 3 2 Opening a G 858 survey ASCII file If you are opening a
100. ection parameters Autoset projection parameters Central meridian degrees 51 Scale factor 0 5666 for 0 9996 Northing meters 0 Easting meters 0 190 In this dialog box we select Enable UTM Transformation which will cause the coordinates to be output in UTM format Additionally we set the Northing and Easting parameters equal to 0 This will make it easier to add offsets later We also allow the computer to choose the prime meridian The new GPS screen is shown below Bn P5Test txt E 8 m Hi NEM ESI Emm ns LLL ES EUUNHEHININ Hm m NEH HHININI BI SU EE ee ee pu a _ L ui TIE TRETIE i ee a qu Hm E ANNANN E i mm umma Be 2 E BIERBIINIEENI pE EmIEINEI Em mul HL HL mumu om Eaa i Now we would like to graph this in a local coordinate system e g instead of using the huge numbers that are given from absolute UTM coordinates we would like to shift all points by a given amount so that the final numbers are more manageable To do this we can set offsets Again we go to the
101. ectrometer are in binary format These files will contain GR 820 as part of the filename Data file records must end with a MagLog NT time stamp formatted as MM DD YY 55 555 159 160 Gps_file name of the MagLog NT location data file to be processed This file will usually contain GPS as part of the filename GPS file records must contain NMEA GPGGA data and end with a MagLog NT time stamp formatted as _MM DD Y Y_HH MM SS sss If GPS records contain the GPS checksum will be verified A sample acceptable GPS reading 1s shown below GPGGA 114804 00 1838 5075 N 11228 2062 E 1 8 01 0 00058 M 00052 9 M 08 10 99 09 05 02 530 e ine file name of the MagLog NT line file to be processed This file will contain the line number as part of the filename This file is created by Maglog NT and should list the times that each line starts and stops A sample line file is shown below START INE 07 108710799 09205 02 251 STOP LINE O0 09 10799 09205220 o 0 START LINE 1 08710799 097051253074 STOP LINE 1 0S 1057 99 09 05 995501 161 11 2 3 Interpolating Other Data Sets It is possible to interpolate additional data sets to the magnetometer time using the MagMap2000 GPS Interpolator Wizard This involves a simple linear interpolation based on time stamps in the data files to be interpolated and a magnetometer data set with time stamps time stamps means that every reading has a time associated with it when it arrived at
102. ed the operation to perform one of the following dialog boxes or windows will appeat 4 3 1 Shifting a line Figure 18 Type in the X and Y field the offset to the new location then click the left mouse button on the OK button or pressed the ENTER key Every position of the corresponding line will be shifted by the X and Y offset For example in the survey plotted in Figure 10 if you shift by X 2 5 and Y 50 LINE 0 you will obtain the picture in Figure 19 Figure 19 4 3 2 Reversing a line There are three options for reversing a line A line can be reversed mirrored in the X and Y directions in the X direction only or the Y direction only The last two options should not be used for horizontal or vertical lines 56 For most cases select Reverse In Both Directions Figure 20 For example in the survey plotted in Figure 10 if you reverse LINE 0 you will obtain the picture in Figure 21 4 3 3 Correcting a walking deviation There are two options for fixing a line deviation A line can be deviated in the X or Y direction If your line is vertical and you did not walk straight and end up off line at the end of the line select deviate in the X direction If your line was horizontal select deviate in the Y direction Figure 22 For example let us assume that in Figure 10 you walk off line on LINE 0 and really end up at the end of line at X 2 5 and y 600 To fix this problem sele
103. editing operations if you edit magnetometer data associated with the standard G 858 position map you will need to repeat the editing operations if you wish to use the GPS map with the data Since most users only use one type of map this shouldn t cause any problems You can have as many flags as you wish The flags should also be visible on any contour plots you generate It is necessary to close a contour plot and reopen it to see the added flags Future additions to this program may include a table output of the anomaly positions 5 7 2 Removing a flag You can remove flags from your map by right clicking on a portion of the magnetic profile and selecting the menu option Remove all flags 5 7 3 Locating a position You can locate a position by moving your cursor onto the part of a contour map or GPS whose position you would like to know The position will be shown on the lower right hand corner of the static bar at the bottom of the screen 6 Base station and survey readings The Earth s magnetic field varies over time periods on the order of seconds to hours similar to survey periods The variations are caused by internal changes in the Earth s magnetic field and the distorting effects of the solar wind The distortions result in micropulsations and magnetic storms that occur at any time and during the daylight hours there are diurnal or daily magnetic field changes Diurnal and micropulsation variations may
104. eld Plot Field in 20 Contours Plot Mag Field in 3D Surface Plot Stack Profle On Plot Sensors Setup Plot All Sensors Dont Plot Any Sensors Zoom ln Stack Profile oom out Stack Profile This should bring up a menu that will allow us to select the sensor we want to plot Sensor 1 Our stack profiles are shown below 0 0 bin 1 Map with stack profiles plotted At this scale we can see some anomalies but we would like to zoom in on them to characterize them more accurately We can right click on our map and select Plot Stack Profile on Top of Map From here select Zoom In Stack Profile as shown below Shift Grid Reverse Grid Rotate Grid Grid Setting Export Plot Mag Field Plot Mag Field in 2D Contours Plot Mag Field in 3D Surface eel Flot Sensors Setup Plot All Sensors Don t Plot Any Sensors om n Stack Prof Soom out Stack 1 Au Pre Note We can also change the height of the stack profile peaks by using the and keys After zooming a few times we get the stack profile shown below 226 18 4 2 1 CHARACTERIZING AN ANOMALY THROUGH THE STACK PROFILE There are a few things we can immediately tell from looking at the stack profile One thing is that we have a few objects that look linear O 70_bin M ER SL ee a UE We can tell this because there are several anoma
105. es SEA EM Geometry IMPORT OPEH SAWE PRIHT Metal Mapper 4N550_266_Field_PR 13 0 stn Local system transformation Replace positions From File p rp p p p p p p p p p p mL p pc ppc pr pp p The warning will appear 80 magmap2000 e This will replace ALL positions on the screen as with positions Fram the File wnuld vau like bo proceed Click Yes and a dialog box opens for you to specify the replacement file name Make sure you check the New coordinates are Longitude and Latitude box at the bottom of the dialog if you want to output position data in Lat Lon i e this box should be checked only if the new cootdinates are to be geographical When you click Open the transformation routine will run Look in E Mir e EJ EH z3U30145 corr dat Sil net ing B 4 pt ii Sl base station jpg nek md 50075 50050 bin El transformi Jjpa Te new Features pdf EH 50075 50050 dat ctransFarm jpq E new features Sx 23030145 BMG PA nelia doc new Features eng sxiw EHI 3030145 dat net eps replacel jpg File name cata MimyA Files of type All Files Cancel Open as read only The position screen will now be updated with the new positions and may look like this 81 4N550_266_Field_PR 13 0 stn ES _ ra I ee E E E DR LZis aa a re Ee iniii o
106. gmap Fil NO VALID BASE STATION FILES ARE CURRENTLY IF You did setup base station while doing survey Please first open the base station file s from the menu t 5 00 dy 0 00 drag dist 45 00 7 00 dy 0 00 drag dist 2 Export MagPick profile Initially read every samples from MagPick oen Here is a portion of the output file we obtained X 008 22 227 122 1864991037 37 Note In this example the first magnetometer had valid readings and the second had a series of O readings This is evident when we look at the output file one line corresponds to the first magnetometer and the second corresponds to the second magnetometer Three fields are always outputted 4302225 1849192 37 4301530 4302233 1849200 37 4301537 Data 50199 07600 0 00000 50096 44800 0 00000 175 13 Saving your editing Magmap allows you to save your editing only in the G 858 ASCI format so can use your favorite editor or spreadsheet to view or edit your data The Save option is not available with any Maglog NT files This applies to the following e Any Maglog NT survey files e Any G 858 files that stored GPS data that was then opened as a Maglog NT file If you want to view this file in its ASCII form you need to use the program bintoasc exe as described below To save a file select File from the menu then Save or Save as
107. he rest of the grid will be correctly located If the quality of reference points is not known you can use some number of them to obtain a least squares fit solution to minimize the errors The fitting process is done automatically when more than 4 points are used in the solution MagMap2000 allows user interactive solution computing as shown below gt 2000 File Edit wiew Scale Filter Gps Survey Setup Window Help Grid Setting ECT Map Offset Between lines N EM Geometry Metal Mapper Local system transformation D ae amp j F IMPORT SAME PRIHT REGOLIT AM550 266 Field PR 13 0 Replace positions From File es Coordinates network 1 I 1 I I Li 1 I I I I I I i 1 r rT rm rm riri rmi rmrm rmi rm rm mimm mrm rm nmT i rm 83 As before open the Survey Setup and select Local System Transformation The following dialog is displayed Local Global Coordinate Transformation S GLOBAL Y GLOBAL LOCAL Y LOCAL 1 B 5243 regar Ug 417 921 18 47 11 68 21 56 2 6048539 0 0 2 4 13 fos 3 B 4 774 fend eae 0 1950 2 33 afd EAE 4 B b133 252639 1300 0 3 15 1 38 3 r 2 B BD 4 reggo 1300 1950 2 90 LF 3 31 Add point Remove pamte Modify point Remove all Save points Load points Solution Information Fseuda palynamial transtormation 2 1 4e
108. hen in fact you have just walked a little faster or had a GPS error that made the distance larger 7 5 2 3 DESTRIPING PARAMETERS DIALOG Next Magmap will bring the data into the destriping program and report the statistical findings You should see a screen such as the one below Destriping parameters Data file ts anualssMagmapSE E sample Files ample da Output File Lines in file 353 2 mir p A ma 504 08 cells 2 Y min 53 Y max 58236 Y calls 85 Interval 0 96628145 Destriping azimuth 30 59348731 lherations o Iteration step nT pa change nT Eo Restore default lt Back Cancel Here you will get a report of the data e min X max Y min Y max These are respectively the minimum and maximum X and Y values found during a search of the file e X cells Y cells these are the number of gridding cells calculated based on the interval specified below e Interval this should approximate the average distance between adjacent points For a series of data points equidistant there should be no performance or accuracy gain by specifying a smaller interval However for points which are not equidistant a smaller interval may help with accuracy Usually the default value works well for most situations e Destriping azimuth This is the angle between north in your gridding system and a line drawn perpendicula
109. his is the last option available but should not be used for opening individual files Magmap has the ability to manipulate many different file types but it needs to know what type of file to expect Since this option doesn t give Magmap any hint of the file type the resulting behavior is unpredictable It is more useful to use this option to see what is in your directory and then go to the appropriate file type selection to actually load your file 3 4 Defining the grid G 858 simple survey mode or G 856 only When you open a G 858 simple survey mode or G 856 file you will need to define the parameters of the grid This does not apply to the G 858 s mapped survey mode because the magnetometer has already stored the coordinates of the positions In the Grid Orientation dialog box Figure 8 you will need to enter several parameters e First position origin this is the origin of the survey s first position e Mark spacing this is the distance between two positions e Linespacing this is the distance between two lines e Survey direction this is how you walked relative to the first position You cannot cancel the settings The Cancel button is grayed out You must set all the parameters to plot the map 46 You will see later that you can change these parameters and even use the grid setting for mapped survey mode Grid Orientation Figure 8 3 5 Conclusion Regardless of the way you import your data by down
110. ht click the mouse button on the green area of the map e To shift the selected positions by an X or Y offset select Shift Selected Position s By To delete the selected positions by an X or Y offset select Delete Selected Position s This will not delete any readings but will cause the data to be linearly interpolated between the remaining positions e To shift the selected segments by an X or Y offset select Shift Selected Segment s To reverse the selected segments select Reverse Selected Segment 8 To reverse and shift the selected segments select Reverse And Shift Selected Segment s by e To delete a segment select Delete Segment This will delete the readings of every selected segment 2 3 How to line up positions along a slope You can create a triangular back edge useful e g if your survey is bounded by a road or a fence at an angle to the grid by selecting the positions you want to move Then right click the mouse button and choose Line Up Selected Positions Along A Slope Then you will enter two coordinates The positions will be moved to lie along the line you have defined 2 4 How to undo the previous operation Select Edit from the menu then Undo You can only undo the most recent operation 2 5 How to view a profile of the readings e To plot a profile of only the readings between two positions click the right mo
111. ically feasible MagMap2000 provides methods to deal with of these potential problems see the following section 6 2 Setting diurnal parameters base station only You can access the screen that will allow you to set diurnal parameters by selecting the menu option Diurnal setup and then the menu item Diurnal Parameters The resulting screen allows you to adjust the base station s clock to correspond with the magnetometer clock Additionally you can choose to add a constant value to each outputted reading Diurnal Setup Figure 64 6 2 1 Adding a bias to diurnal magnetic values You can add or subtract to all the base station magnetic readings a constant magnetic field In the bias to add to diurnal magnetic values just type any positive or negative value you want to add to every base station magnetic field The Diurnal column in the XYZ file consists of the difference between the sensor reading and the base station reading plus the offset entered in this dialog box This is in case you wish the diurnal values to be in the 50 000 nT range rather than relatively small positive and negative values 6 2 2 Adding a bias to diurnal clock values A time mismatch between the base station and survey data will cause misalignment of the data values and cause subtraction of the wrong base station value during the correction One can imagine that if the base station data curve has large variations a mismatch wou
112. id point at status bat 5 2 Shaded Relief plot The shaded relief plot is used to give a different view of the data similar to what you might get via a contour plot but more customizable It is produced by assuming there is a light source above a 3 D topographical map of the data The location of the light source is user defined and the resulting shadows are graphed on a 2 D plot You can decrease the effects that huge spikes have in your graphed data by using scaling factors that work to reduce the influence of the spike You can also adjust the viewpoint by changing the relative location of the light source To produce a shaded relief plot you need to first obtain a contour map See the section on contour maps for instructions on how to do this From here right click on the mouse as shown below GPSTest txt 2 OF x Plotting Mag Field in 2D Contours for ANALOG DEVICE 4 Plot Sensors Setup Plot Alli Sensors Set Min and Max Field Set Grids 2D 3D Plot Only 56 000 50 001 50 002 20 005 50 004 50 005 50 006 Ctri left mouse drag to Zoom Press to reset After you select Set Min and Max Field you should obtain the following dialog Set Vertical Scaling Ed Maximum field 0021 9 Minimum field 49478 Revert color scale Restore Detault Iv Equalize colors Colors fio Shaded relief Cancel From here press the Shaded Relef button to get a dialog that will let you set the
113. il software corpscon corpscon html Here is how MagMap solves the transform problem Example 1 Point for Point Mark replacement You have State Plane positions for all survey marks including end of the lines or State Plane coordinates The following file must be manually generated XGLOBAL YGLOBAL XLOCAL YLOCAL LINE MARK 7606142 127 7252837 023 1300 0 39 26 7606092 261 7252834 938 1250 0 39 25 7606042 396 7252832 853 1200 0 39 24 7605992 530 7252830 768 1150 0 299 25 7605942 664 7252828 683 1100 0 o9 22 7605892 799 7252826 598 1050 0 ow 21 ou want the surve rid in Latitude Longitude The first string is the header and is not used The second line has two columns labeled XGlobal and Y Global which contain State Plane UTM or Lon Lat coordinates two columns with local X Y 858 coordinates and columns for the line and mark numbers The program actually uses only the State Plane and Line Mark pairs All marks must be present in the file omitted pairs are removed from the data in memory a warning message is displayed Integer numbers must be used for Line Mark pairs Note When data is exported magnetometer data is interpolated between existing marks To perform the transformation load the G 858 STN or BIN file and select Survey Setup Replace positions from the menu lt Magmap 000 File Edit View Scale Filter Gps Survey Setup Window Help m Grid Setting eee ci oe Map Offset Between lin
114. ile presents a way of looking at the magnetometer data of several lines at the same time It scales the magnetometer data over each individual mapped survey line as seen in the example below 2 100 NNNM Stack Profile for an G 858 survey Note the similarity of the second line X 74 to the plot of our magnetometer readings 96 We have zoomed in on the left line X 74 so that we can compare it with the magnetometer readings below 72_100 bin 2 Plotting of readings from Line 37 mark 2 to line 37 mark 0 49673 766 4887 7 580 13 48 10 300 13 49 19 900 Magnetometer Readings for X 74 We can see that this early peak also appears above on the stack profile Currently Magmap supports handheld land based surveys such as surveys done with the G 856 and G 858 magnetometers 97 Note Stacked Profile is not available for GPS date 5 3 2 How to plot a stack profile To plot a stack profile you need to start from the mapped screen 2 100 NM Shift Grid Reverse Grid Rotate Grid Grid Setting Export Plot Mag Field Plot Mag Field in 20 Contours Plot Mag Field in Surface Plot Stack Profle On Top Fy Plot Sensors Setup Plot All Sensors Dont Plot Any Sensors zoom n Stack Profile Zoom out Stack Profile pe eet ee From y
115. ine For example in the survey plotted in Figure 10 if you delete LINE you will obtain the picture in Figure 28 Figure 28 LINE 0 has been completely removed from the survey 4 4 Selecting and editing segments continuous survey mode only A segment is defined as the set of readings between two positions 60 In discrete survey mode there is only one reading per position and located at the position itself therefore there is no segment In continuous survey mode readings are acquired between positions and linearly interpolated between them To select a segment right click the mouse button between two positions on the direction symbol arrow Segment operations are only available for continuous survey A pop up menu should now appear on the screen Figure 29 e To shift the segment by an X or Y offset select Shift Segment By To reverse the direction of a segment select Reverse Segment To correct a walking deviation error for example you did not walk straight between 2 positions and end up at an other line select Add Segment Deviation To rotate a segment select Rotate Segment e To plot the magnetic field between 2 positions select Plot Mag Field e To delete a segment select Delete Segment This will delete the readings between the two positions Every operation on a segment is basically the same as operating on a line You can think of a segment as being a line with
116. ing depth given in the Applications Manual for Portable Magnetometers Chapter 5 18 7 2 Getting a position of the anomaly from the contour plot This is a general rule of thumb that helps you get the position of the object from knowing the minimum and maximum of the dipole We begin with a dipole that we previously looked at This figure shows how you can find the location of the anomaly by finding the minimum and maximum Namely 1 Find the center of the minimum 2 Find the center of the maximum 3 Draw a line connecting the two 4 Find the center of this line 5 The location of the anomaly is at the center This is only a rule of thumb but it is useful when you have a large area and don t know where to start digging 18 7 3 Additional Observations You might also take the opportunity to compare the results from the mapped survey with those obtained from the same survey using the GPS As surveys get larger and larger it becomes more difficult and expensive to lay out accurate mapped surveys Additionally as there are fewer and fewer definite position points the errors are greater because it is difficult to accurately time interpolate position points for each magnetometer reading Even small changes in speed can make a large difference over a long line However with smaller surveys the error of the GPS usually around 1 2 meters can be larger than the error recetved from time interpolation We can attempt to reduce
117. ing on policy Then data is parsed the same way as for Generic Serial Device Channel names can be assigned by default in this case program counts all available channels or can be defined by the user In latter case some of the data channels could be omitted for instance only speed could be extracted from the VTG message and meaningful channel name can be assigned Below this kind of data is referred as prefixed data GPS VTG message is used below as an example but procedure works the same way for any kind of prefixed data To use this feature sequence of operation is not important either of following conditions should be met e At least one GPS or SURFER file should be loaded Those files should refer to the same time interval as prefixed data e Survey file should be loaded This includes GPS line number file magnetometer or other devices After all this information is loaded prefixed messages could be loaded from the same GPS file e Prefixed data should be acquired with MagLog program at least have time stamps at the end of the message Time should sequentially increase As a result user is able to export speed values with its positions pretty much the same as it is done for magnetic field 10 1 Example using GPS VTG messages In this example we load speed values from GPS VTG messages in addition to all other information included by default into MagLog survey Prefixed data could be loaded
118. itions changing the direction of lines rotating lines and deleting parts of lines or entire lines It also provides a means of performing diurnal corrections plotting the acquired magnetic field values and filtering them for spikes dropouts or leading errors Vertical and horizontal longitudinal and transverse gradiometer data is supported In cases where there 15 GPS data MagMap2000 has facilities to smooth this data and use these coordinates in place of mapped coordinates Finally the program will export data for surface plotting programs such as Golden Software s Surfer and GeoSoft s suite of analysis plotting programs 1 1 Program Flow Overview The flow diagram below is provided for reference in the following discussions and will assist the user in understanding each step of the data processing procedure G 858 Data Format MagMap Function Binary Data Files 1 5 File Import Binary Data BIN extension File Save optional ASCII Data STN extension File Export Surf Data GeoSoft xyz DAT extension Data Flow for the Magmap program 1 1 1 Downloading Data from the G 858 The time position and magnetic field data are stored in the G 858 console in one of 5 files numbered 1 through 5 The data are stored in a compressed binary format for maximum use of the available RAM While the user may select ASCII download via RS 232 with a program of his choosing i e Procom this can take up to 2
119. lains how to open an already downloaded file and go directly to paragraph 3 4 Defining the grid G 858 simple sutvey mode or G 856 only 3 2 Opening a survey file You can open several types of files that are already on your PC G 858 binary compressed files e G 858 ASCII file Simple Survey Mapped Survey and Base Station e G 856 ASCII file Survey and Base Station e Maglog airborne projects e Individual Maglog Files Maglog NT Maglog lite Magsea projects e Individual Magsea files e MGS files Marine Gradiometer Software e G 858 bin files with a csv file that gives corrected GPS positions e Surfer Fiber dot or XYZ files Note Take care in selecting the proper category The program acts differently for different types of projects And there are several ways to open these files 3 2 1 Opening a file using the menu or the tool bar There are several ways you can bring up the open dialog box Figure 3 e Select from the menu File then Open Or click the left mouse button on the open toolbar button Or press the CTRL and keys simultaneously 3 Samples c e Base bin survey bin Open G 858 Compress Files bin Figure 3 Once the open dialog box appears on the screen select the desired file then click on the Open button 36 3 2 2 Opening a file using Drag amp Drop Windows Explorer You can use Explorer to import several survey files Sel
120. large a particular anomaly is and also where it occurs To do this we will need to set up a series of good grid lines and then use Magmap s zoom feature to look at pertinent features To turn on the lines go to Scale and select Grid Lines You should get the following menu Set time grid parameters Time axle Iv Draw arid lines Auto grid interval step 1 miri Field axis M Draw arid lines Auto grid interval step 5 Decimals NN Choose Font Cancel Grid Lines dialog box Here we have chosen to manually specify our grid lines We have chosen intervals that are pertinent to our survey e g the survey is 100 meters wide so it makes sense to scale and try to locate anomalies on the scale of 1 5 meters We have disabled Auto gridding because it is more difficult to find the values that will be assigned to the intervals When we press OK our appears as follows 223 O 0 bin 1 Map with grid Note Magmap will apply the grid options to the active window Make sure that you have selected the window you want to grid 224 18 4 2 Using the Stack profile The stack profile is particularly useful in a survey such as this where the lines are straight and parallel We can plot a stack profile on our map by selecting an endpoint and right clicking to get the menu Shift Grid Reverse Grid p Rotate Grid Grid Setting Export Plot Fi
121. ld yield even larger magnitude inaccuracies than if a smoothly varying curve was used In turn if the base station data curve is essentially flat constant during the survey period there would be little concern about the effects of a time mismatch One may use the bias shift option to apply the shift needed to match the start times of the base station and survey data The period of the base station data file should be equal to or greater than that of the survey data In the bias to add to diurnal clock just type any positive or negative value in seconds that you want to add to the time of all acquired magnetic field readings of the base station This will allow for you to correct for errors due to the clock of the base station being different from the clock of the magnetometer 6 2 3 Performing Diurnal Correction Diurnal correction is done automatically upon export of the edited file to Surfer or Geosoft format Both the Base station and Survey files must be currently open and be synchronized in day and time You must also select the diurnal column in the export settings when exporting the Surfer or Geosoft file Note that an exported file in dat or xyz file format can be reloaded into Magmap for viewing or further editing 6 2 4 Despiking base station data We despike base station data in the same way that we despike magnetometer data Please see the following chapter for a description on how to do this 6 2 5 Smoothing ba
122. le matches the time of the survey 3 Importing a survey 3 1 Downloading a survey from a G 856 or G 858 Magnetometer 3 1 1 Select import from the menu Select Fre from the menu Choose Import G 856 Data if you have a G 856 magnetometer or Import G 858 Data if you have a G 858 data The dialog box in Figure 1 should appear on the screen Setup G 858 For Download Turn on G 858 Select data transfer menu and press enter Select PC controlled transfer and press enter When you are ready click on OK Cancel Figure 1 Note Most of the following examples use the G 858 magnetometer but the procedure for downloading data from the G 856 magnetometer is the same 3 1 2 Setting the G 858 magnetometer for upload In the G 858 Initial Menu select DATA TRANSFER by moving the up or down arrow key Press the Enter key to go to the Data Transter Menu In the Data Transfer Menu select TRANSFER UNDER CONTROL OF PC and press enter The G 858 is now ready to download the sutvey 3 1 3 Setting the PC for downloading Once your G 858 is ready for downloading click the left mouse button on the OK button or CANCEL to abort The G 858 download setup dialog box should now appear on the PC screen as shown in Figure 2 32 G 858 Download Setup msema d E Program Files MagMap4Y6 datasetl bin Program Fileskhdagapsb dataset bin FileskhdagapBSB5dataset3 hbin
123. lies on the stack profile that have about the same height and width and can be arranged in a line This is characteristic of objects such as pipes These particular anomalies came from a wooden pipe wrapped in steel wire that was buried at the survey site in the 1800s The wood had long since rotted away but the steel wire surrounding it was picked up by the magnetometer You can also look at other anomalies and try to get some basic characterizations such as depth X and Y coordinates and width You can even begin to guess what type of object it is For more discussion read Applications Manual for Portable Magnetometers by S Breiner A thorough discussion on interpretation of anomalies is gtven in Chapter 5 18 5 Exporting the data 227 This data can now be exported for further analysis The technique is a little different than the technique we saw in Chapter 17 For one thing we have no GPS data to export We can export our data by selecting Export from the file menu We get the dialog box shown below Export Setting Fa Sensors type One sensor 1 or left or tap or front FORE direction Bias value for magnetics Sensor separation C iz File format Surer h F C Output format ees wo SENSORI SENGO Y SENSOR E DIHBNAL ER Lus DATE LINE Output file sPrafiles sdministratarsD esktep M agmap FilessAI 1 320 70 dat BROWSE SAVE
124. loading your survey or by using the open dialog box Figure 3 or using Explorer the folowing window Figure 9 will appear on the screen Some surveys will only have the lower window mapped initially open This window will appear if you have This window will appear if you have imported a base imported a survey file station file E Magmap2000 _ File Edit View Scala Fiter Plot DiumalSetup window Hep Flat Fiter Plot DiumalSetup window Hep Window Help SEH Ee NES Qa ae mem Base ee ee ee ee Se C ep et ep Pe et ee B I ILLI I L EE E For Help press F1 Reading Number 15842 FIELD 54513 285 07 26 85 15 15 29 Figure 9 Note If no profile is initially open you can create one by right clicking on the mapped screen and selecting Plot Mag Field If you click on a position point it will the profile of the line corresponding to the position point clicked If you click on another part of the map you will get a profile of all the data 48 4 Editing of the map 4 1 Map user interface description and definitions A start of line is the first position of a line and is represented by a green square Figure 10 An end of line is the last position of a line and is represented by a red square Figure 10 A position called Mark in G 858
125. lone Note It is usually recommended to do a second smoothing after using jump to despike because the curve is not actually smoothed Instead the first smoothing spline is used only in calculating whether a given point is a spike If you do smoothing a second time it will smooth the despiked data e Spl Smooth This allows you to turn on a second degree of smoothing that will be done after your first despiking and smoothing have occurred e Parameter This controls the degree of smoothing for the second smoothing Note You apply any change in parameters except Line Number by right clicking on the gray heading buttons E g to change the Despike option we would press Despike This will then give a menu that will allow you to change the value and apply the option to all lines You can also change the parameters for an individual line by selecting the line and pressing Change Line Parameters Below we have chosen to edit the parameters for line 4 142 Line smoothing parameters setup Spl smooth Spl smooth II 4 No 2 Line 0 Yes 10 1 Y es 4 Ma 10 Ma 2 Line 2 Yez 4 Linet 3 M 4 Smooth parameters for Linet 4 s M Spline smooth Parameter Line Tes 4 Linet 7 Yes 4 Position despike Jump m o I Spline smooth ll Parameter Change line parameters Cancel We have changed the first smoothing parameter from four to six higher degree of smoo
126. lors technique for contour plot As a recent addition to the program the contour algorithm uses a technique where the colors shown are equalized This is best explained by looking at the plot below which does not employ this technique Bim IB XJ Plotting Mag Field in 2D Contours for Sensor 1 50200 50155 50109 50064 50018 49973 49927 49882 49836 49791 49745 49700 E 40 As it can be seen most of this graph is dominated by color The other colors are sparingly represented and this occurs because each color represents a roughly equal part of the total magnetometer range Since the range is divided up into equal parts this technique will show a bad contour plot if a drop out exists or some small noise exists because then the range is a lot larger and each color must span a much larger range For instance if we graphed the above and had one drop out in the data that we didn t filter we would probably see an entirely red graph because blue would represent a range of about 0 10000 green a range of about 20000 30000 and red most of the valid data taken We can solve this problem by using a technique of equalizing colors This means that each color is represented in the contour plot the same amount In the graph below we see this at work 0 70 bin 2 Plotting Mag Field in 2D Contours for Sensor 1 ee SO ea
127. ments the same way as a single segment see paragraph 4 4 2 Reversing a segment page 62 4 5 2 6 REVERSING AND SHIFTING A GROUP OF SEGMENTS CONTINUOUS SURVEY MODE ONLY You can perform a reverse and shift operation on a group of segments all at once 4 5 2 7 DELETING A GROUP OF SEGMENTS CONTINUOUS SURVEY MODE ONLY You can delete a group of segments the same way as a single segment see paragraph 4 4 6 Deleting a segment page 66 4 6 Selecting and editing the survey grid To select the grid right click the mouse button on the green area of the map A pop up menu should now appear on the screen 74 Figure 56 e To shift the grid by an X ot Y offset select Shift Grid By To reverse the direction of every line or every other line select Reverse Grid e To rotate a select Rotate Grid e To change the mark and line spacing select Grid Setting e To export your survey to Surfer or Geosoft Analysis and Plotting Software select Export To plot every magnetic field reading of the survey select Plot Mag Field Once you have selected the operation to perform one of the following dialog boxes or windows will appear 4 6 1 Shifting a grid Shift grid Figure 57 Type in the X and Y fields the offset to the new location then click the left mouse button on the OK button or pressed the ENTER key Every position of the survey will be shifted by the
128. moothing by pressing Close and Appl The final map shows our smoothed positions GPS data with smoothed path drawn 194 16 5 Other operations 16 5 1 Setting Offsets In this survey as in most surveys the positions of your magnetometers will not be the same as the GPS positions reported This can be easily seen by looking at a contour map generated by Magmap for the example data set Plotting Mag Field in 2D Contours for AMALOG DEVICE 1 45 400 20021 7 50017 85 450 5001 3 8 500099 300 S0006 0 200020 250 49995 1 49994 2 200 49990 3 40956 3 150 49992 4 49978 5 TOU This should appear to be a grid of 9 circular anomalies However due to the difference between the GPS position and the magnetometer position the actual map doesn t come out that way We can correct this by setting offsets Select the GPS Offse menu option under GPS GPS Offset Setup EG Magnetometer offsets e magnetometer 1 T tj oS magt dx lt 0 dy 0 amp mag2 dx dy maga dx lt 0 dy lt 0 2 magnetometer 2 7 E C im typical for hand held typical for marine or airborne Harizontal X offsets are positive to the right of the GPS and negative to the left of it facing inthe direction of motion magnetometer 3 77 ERI aoe Parameters to calculate direction of motion Points to look forward 5 Points to look backward 2 Offsets Multiple offsets se
129. multi point spikes from anomalies is the number of points they span It 15 reasonable that we will not see 10000 gamma anomaly for 1 seconds e g about one point for a magnetometer taking readings at a rate of ten times per second However if we saw this jump last for a long time hundreds of readings we would probably believe that it is an anomaly rather than an incidental spike A lot of this 1s also dependent on the speed of the operator We can also use the height of the anomaly to characterize an anomaly A jump of one gamma might be considered to be noise whereas a jump of 5000 gamma might be an anomaly or a spike 7 2 Atypical despiking session A typical despiking session usually involves two activities e removing drop outs zero readings e identifying and removing spikes non zero anomalous readings over a short duration When we remove drop outs we try to remove the effects due to being near a dead zone or near a very large ferrous mass These are zero readings that can show up in the data for short to long periods of time usually showing that the magnetometer was operating under conditions where good readings were not possible Since these readings are not valid in our data and can overwhelm our efforts to see smaller anomalies we remove them We can choose between linearly interpolating between bad readings and removing the readings from the file without linearly interpolating them Because most gridding pr
130. n To e To shift the position by an X or Y offset select Shift Position By e To delete a position select Delete Position This will delete only the positions The locations of the nearby readings will then be re interpolated using the positions that are left 2 2 2 Selecting and editing entire lines To select a line click the right mouse button on the start of line symbol big green square ot on the end of line symbol big red square To shift the line by an X or Y offset select Shift Line By To reverse the direction of a line select Reverse Line To correct a walking deviation error for example you did not walk straight and end up at another line select Add Line Deviation e To rotate a line select Rotate Line e To delete a line select Delete Line This will delete the readings of an entire line 2 2 3 Selecting and editing segments To select a segment click the right mouse button on the direction symbol arrow located between two positions Segment operations are only available for continuous surveys To shift the segment by an X or Y offset select Shift Segment By To reverse the direction of a segment select Reverse Segment To correct a walking deviation error for example you did not walk straight between 2 positions and end up at another line select segment Deviation To rotate a segment select Rotate Segment To delete a segment sele
131. n the status bar The first item shows the magnetic field amplitude the second item is the reading number in the survey and the last one is the time of the reading The base station scale tool bar is similar to the map scale tool bar described in paragraph 4 1 page 49 except for the last button True map coordinates which is not available and grayed out 6 4 Setting plotting parameters When you click the right mouse button in the plotting window you will see a pop up menu as shown in Figure 66 Figure 66 By default only the readings for the first sensor are plotted You can plot if you wish the teadings of the second sensors or simultaneously the readings of both sensors You can also change the scaling parameters by selecting Set Min and Max as shown below in Figure 67 Set Vertical Scaling X 54532 515 54474 353 Figure 67 You can set the maximum and minimum magnetic field value to be plotted in the first two items of the dialog box You can restore the default value by clicking the left mouse button on Restore Default 6 5 Base station file formats The base station file may have any name with the BIN extension for a binary file anda STN extension for an ASCII file The BIN file is a raw data dump and not stored in a user readable format do not modify files of this type Depending on the magnetometer used for the base station the STN data formats would appear as follows G 856A AX
132. nates Network gt Magmapz2z n File Edit wiew Scale Filter Gps Survey Setup Window Help Grid Setting um E Led id T Map Offset Between lines st EM Geometry Local system transformation Replace positions From file If some of the marks are outside of the polygon defined by the triangle mesh they will be removed If the transformation appears to be miscomputed use the Undo button to restore original positions in case of error and check your reference point file for errors 87 5 Other views of Readings Magmap has the ability to display readings in different ways depending upon what kind of survey you have 3 D plotting capability is included in Magmap The purpose of the 3D displays is to give a quick ovetview at the data They are not intended for in depth data analysis or presentation but can be printed 5 1 2D contour and 3D surface plots for magnetic field readings 5 1 1 Creating a 2D or 3D plot When tight clicking the mouse button to edit the grid two new options Plot Mag Field 1n 2D Contours and Plot Mag Field in 3D Surface are included in the menu as follows Shift Grid Reverse Grid d Rotate Grid Grid Setting Export Plot Mag Field Plot Mag Field in 20 Contours Plot Mag Field in 30 Surface Plot Stack Profile On Top Of Map Note Plot Stack Profile On Top Of Map may not be available for some types of surveys specifically GPS survey
133. ne can look even deep with higher spline factors What if we want to look at only the surface features for instance if we are doing an archeological or UXO survey we may want to accentuate the higher frequencies and remove the deeper geologic signal In this case we apply a high order high number spline filter to the data and THEN CLICK THE DIFFERENCE button so that the data that is presented when we press review is the difference between the raw data and the splined data Then in this fashion only the higher data is saved into memory when we press the Accept button im 2 dat zinixi Smoothing degree a 4 Channels to apply MiBOTTOM ACG Previews Accept Hemova Cancel ERNETEN IN ESE EEE DARET T TS Then when we contour the data we get high frequency small target data display 40 20 6 10 2 30 40 50 70 80 100 ra VI The Problem Noise spikes due to operation of the sensor close to the dead zone see dead zone sensor orientation discussion in technical report MTR 120 can be troublesome to remove However with our new range despike and spline filter modules the data clean up is simple and quick The Solution Here is a sample of data corrupted by poor sensor orientation 12 l l l l l l l l l l l l l l l m l l l l l l l l First we use the Range Despike tool
134. ng error offsets are most apparent It assumes that the lines are run straight and parallel 7 5 2 Use of the Destriping data wizard The input to the Destiping program is the dat file exported from MagMap after all filtering and data positioning edits have been made The output of Destriping is a dat file and therefore can be called back into MagMap for viewing However better visual results will result if the data is gridded and displayed in third party program like Surfer or Geosoft When the routine runs it gives diagnostic data about the destriping process which will give the user important information about the success of the process and whether an additional iteration or varied parameter is required 7 5 2 1 FILE PARAMETERS DIALOG Destriping like GPS Interpolator for large marine or airborne files is accessed through the File menu selection Click on File then Destripe Data to access a dialogue box shown below The pertinent parts are 121 e Name of input file This is probably a dat file that was created using Magmap previously It should have space separated columns with X Y and field values at minimum Additionally lines numbers are useful but not mandatory e Name of output file The default name is output dat so it is advised to select new name that is more related to the name of your file e Name for statistics file this 1s enabled if you have selected the option Output Statistics File The stati
135. ning you of duplicate time stamps You can choose to smooth the readings immediately by pressing Yes or you can leave the data as it is and correct it later 3 3 8 Opening a Magsea individual file You can use this option to individually open Magsea files This option will show all files in your current directory not just the files it can recognize You should be able to open files with extensions such as refand DOL If you have readings with duplicate time stamps you should get an error message such as described in the previous section 3 3 9 Opening a MGS file Marine Gradiometer Software This option will allow you to open a MGS file If you have not purchased MGS Tools for Magmap this will not apply to you Otherwise you should read the user manual on MGS tools for further discussions on these files 3 3 10 Opening a G 858 bin file and corresponding csv file The option G 858 bin files and csv file currently supports files that are created from Trimble s Pathfinder software The csv file is a file that has differentially corrected positions that were produced from the Pathfinder program The 858 binary file should have GPGGA data strings recorded as serial data and there should be a one to one correspondence between readings in the csv file and GPGGA strings in the binary file 3 3 11 Opening SURFER dat file MagMap can read and display generic SURFER ACSI files in the same manner as MagLog NT
136. nput check box must be checked to enable the other items on this panel If this box 1s not checked GPS Interpolator operates with unchanged geographical coordinates which results 1n less accurate positions The Transfer UTM gt Lat Lon on output check box us used to generate accurate interpolated locations in geographical coordinates 164 Ellipsoid parameters section The Ellipsoid name list box allows choice of 12 pre defined ellipsoids or a user defined ellipsoid Pre defined ellipsoids include WGS 84 GRS 80 WGS 72 Australian 1965 Krasovsky 1940 International 1924 Hayford 1909 Clarke 1880 Clarke 1866 Airy 1830 Bessel 1841 and Everest 1830 Major axis and Flattening text edit boxes are enabled only for user defined ellipsoids UTM projection parameters section e Central meridian degrees text edit box is used for manual entry of the Central meridian to be used for location conversion This box is disabled when Choose central from data check box 1s checked e Choose central from data causes GPS Interpolator to automatically determine central meridian from the first GPS data file record Automatically determined central meridians are chosen by UTM Zones on six degree centers e Scale factor should usually be left at 0 9996 The text edit box is provided for the rare case where a different scale factor can be useful e False Northing m False Easting m allow entry of offsets to cal
137. o select a group of positions click the left mouse button and draw a rectangle around the positions to select Figure 42 When you have finished drawing the rectangle release the left button Every position inside that rectangle will be selected indicated by a white square as shown in Figure 43 Ml ul ug m m my m m m gm m m Pee Ree eo ee I 9 m m m m m 9 m m m y M y m m m m A fg Ft fg Figure 42 ull ull ug m m gm m gm m gm M NM NM Im ma m y m m m mma m m gym m m m m m my m m NW Figure 43 To select more positions press the control key CTRL and repeat previous operation Figure 44 and Figure 45 n mmn m m m gm my m gm m gm mM NM m m m m wml E E g n u hi E E g Figure 44 PT Ti mnm EEEN ENP ey I m m m m m9 m UN 1 UN i fj UU Figure 45 e To select a single position press the CTRL key and click the left mouse button inside the corresponding position e When you select positions if the positions were already selected they will be deselected Figure 46 and Figure 47 If they were not selected they will be selected pressing the CTRL key toggles the selection 68 E EEEE D m m m m r m mw PPP TT Ty TT Figure 46 mnm n mm mr
138. ograms will grid over the missing data we recommend removing them For more information please see the following discussion on removing drop outs To identify spikes we suggest zooming in on potential anomalies and then counting the number of readings to see if they are really anomalies To zoom in on a section of the map de select the AUTO button and click on the X tool bar button to allow zooming in the X direction Once you are at a scale that allows you to distinguish the anomaly place the cursor on the left and right at the beginning and end of the anomaly and note the reading numbers on the information bar at the bottom of the plot display You can get the number of readings involved in the anomaly by subtracting the two numbers In general we would think that any anomaly greater than one second 10 readings or less at 0 1 second per reading or perhaps less than one second depending on walking or traverse speeds would be determined to be a real magnetic field shift and not some artifact of the survey process Once a true spike is identified it becomes necessary to define the limits of the spike editing process such that actual data is not modified in any way We do this by setting the spike edit parameters by clicking on and then Despike Setup Default values are 5000 nT and 1 reading spike by anyone s definition Depending upon the type of spike identified some iterative trial and error proce
139. ollowing dialog box Set coordinate grid parameters iTi Tere 1 Dialog box for Grid lines menu option time series plot Both dialog boxes behave in a similar fashion so we will discuss the first dialog box this dialog box allows you to set grid lines for X and Y and choose the scaling method The two methods available are e Auto grid interval automatic scaling This assumes you want a fixed number of grid lines and will pick the scaling between each grid line so that you always see the same number of lines on your grid no matter how much you zoom 103 e Manual interval you pick a step that you want The grid lines will remain the same through all zoom factors e g the distance between them will scale so that they always represent a constant value There are also options to e Choose Font You can select the font and color that the grid line numbers will be written in e Decimals specifies the amount of precision displayed in the gridline numbers number of numbers after the decimal point Note The time series plot mesh step is set in minutes The time axis can also have an irregular mesh because different survey lines were taken at different times you may not have a continuous set of readings over the entire time Due to this you may see irregularities in time labels Here are examples that illustrate the two different types of scaling In each example we show the initial g
140. ollowing format NMEA output message format with a GGA message type Magmap has facilities to change from geographical coordinates to UTM coordinates smooth your GPS data and add additional positions to be calculated relative to the GPS 8 2 Loading your GPS data If you used the 858 MagMapper or DataMapper console to store GPS data you will see two menu items enabled These items are e Draw new map using GPS and the features of a regular 858 survey e Draw new map using GPS and the features of an airborne survey If you select either item a new map will be drawn as shown in Figure 69 using only GPS information Each flag is a GPS position fix Every latitude and longitude in the data stream is converted from degrees minutes seconds to decimal degrees within a range of values from 180 00000 degrees to 180 00000 degrees Note If you earlier enabled UTM coordinates to be used in the program the map will be drawn using UTM coordinates and the parameters you selected You can change this later if needed When you export your survey to Surfer or Geosoft Analysis and Plotting Software magnetic readings will be linearly interpolated between GPS locations in latitude and longitude decimal degrees UTM conversion to meters is optional see section 8 3 The user interface for a GPS map window is about the same as the regular map window using flag locations Many of the editing functions that change the coordinates of a location
141. ols use the mouse or press the TAB key 52 You can copy and paste values between every edit control The following commands are common to all edit controls in this program and Windows 95 98 and will not be described for the other dialog boxes When using the keyboard To copy press CTRL and keys or CTRL and INSERT keys To paste press CTRL and V keys or SHIFT and INSERT keys To undo press CTRL and Z keys or ALT and BACKSPACER keys To redo press CTRL and Z keys or ALT and BACKSPACE keys To cut press CTRL and X keys For example in the survey plotted in Figure 10 if you move the position at MARK 1 LINE 0 from X 0 Y 100 to X 2 Y 50 you will obtain the following picture Figure 13 When using the mouse Figure 13 Click the right mouse button and a pop up menu will appear 4 2 2 Shifting a position Shift position Figure 14 Type in the X and Y field the offset to the new location then click the left mouse button on the button or pressed the ENTER key For example in the survey plotted in Figure 10 if you shift by X 2 and Y 50 the position at MARK 1 LINE 0 located at X 0 Y 100 you will obtain the picture in Figure 13 4 2 3 Deleting a position Delete Position Figure 15 If the information reported by this dialog box confirms that this is the position you want to dele
142. oothing routine which when combined with the Range Despike editor offers excellent noise reduction The Solution Bring in the basestation file and then go to Filter Smooth Basestation Data You can select a value from to 10 for the smoothing 10 being the highest filtering Note that the filter curve is shown prior to your acceptance If you go back to Filter and Smooth Basestation Data you can choose Accept which will modify the data in memory Then you can export it or plot it Remember that your original data is never changed bin files but you can save a stn file over the original stn file Basestation data 4 hours Basestation data filter level 4 preview zoomed in tu eo a ar eio ee We ocho Ie bt D ic chal che icicles cae tha iol icici pri SBEHIIBIRRI Basestation data 0 05nT smoothed to 0 01 or better with filter level 4 0 A EE EE SSS OAS Sa SS E E E rer OS OS eS Sar Sea Sr Sera WEMMEL Basestation data accepted NOTE This feature will be implemented on regular data by November 2002 Then you can apply smoothing to both basestation and field data IV The Problem Zooming in to see the data had a maximum limit using the circle with a in it or an X or Y The Sol
143. options for fixing a segment deviation A segment can be deviated in the X or Y direction If your segment is vertical and you did not walk straight and end up off line at the end of the segment select deviate in the X direction If your segment was horizontal select deviate in the Y direction Add Segment Deviation k Figure 34 For example let us assume that in Figure 10 you walk off segment on the second segment of line 0 and really end up at the end of the segment at X 2 5 and Y 200 To fix this problem select deviate in the X direction When the following dialog box Figure 35 appears on the screen type 2 5 and click on Deviate segment in the X direction Figure 35 You should now have fixed your walking deviation as shown in Figure 36 64 Mark2 has been duplicated 4 4 4 Rotating a segment Rotate segment Figure 37 Type in the rotation field the angle of the rotation in degrees from 360 to 360 degrees Type in the X and Y fields the cootdinates of the rotation origin Once you enter all the fields left click the mouse button on the button or press the ENTER key For example in the survey plotted in Figure 10 if you rotate the second segment of line 0 by 90 degrees at the origin X 0 and Y 100 you will obtain the picture in Figure 38 1 Da Poe Pees Figure 38 Mark2 has been duplicated Note Aspect ratio of x
144. ormal readings to count as spikes We can remove spikes using the Despz amp e Setup also available through the menu Despike Setup Feak Threshold 5D Maximum Spike Readings 3 FEET Indo Close In this case these options work well If we used this to filter our drop outs we would need to use more than one point for our Maximum Spike Readings This is how the program determines it is dealing with a spike Since spikes that are due to error tend to be short in duration a few readings if you have any more readings composing your spike than the Maximum Spike Readings Magmap will assume that this is not a spike and it will leave it alone After you are done with this press Apply Note Magmap keeps a history of the changes you have done to your data If you don t like the changes you made you can press Undo to get back your original data In a few cases e g where you remove the drop outs or linearly interpolate them you will not be able to undo your changes after your first despiking Be careful and undo any changes you don t want to keep before despiking You should get the following 188 fe 880T est with dropouts_txt Scaled magnetometer data with drop outs removed If you want you can re scale this again to fit the bounds of the data You can also remove all your drop outs by despiking rather than by selecting Remove Drop outs Be careful doing this though b
145. osition points selected 217 7 0 70 bin 12 Shift Selected Position s By Delete Selected Position s Line Up Selected Position s Along amp Slope Shift Selected Segment s By Reverse Selected Segment s Reverse And Shift Selected Segment s By Delete Selected Segment s aI Oy el el Here we have selected the three position points we can pick these out by looking at the statistics on the bottom of the screen We search for X 52 or Line 26 After we have deleted the line the map should appear as follows 7 0 70 bin _ 150 ee Mg Ng 9 gu yg Map with a line deleted We now need to shift all of the other segments over so that our other map coordinates will be correct To do this we need to select all the segments and then press the right mouse button to bring up the pop up menu From here we can select Shift Selected Segment s by as shown below 218 0 70_bin Shift Selected Position s By Delete Selected Position s Line Up Selected Position s Along Slope 4 I 4 4 Shift Selected Segment z By B an E q U u a V T ni Reverse Selected Segment z Reverse 4nd Shift Selected Segment s By Delete Selected 5 Since we want to move all of the segments 2 meters to the left and we don t want to change Y offsets at all we should use an X offset
146. our mapped screen right click on your mouse and select Plot Stack profile From here you have several options e Plot sensors setup allows you to choose which sensor s you would like to plot including the pseudo gradient if available e Plot All Sensors will automatically plot all sensors e Don t plot any Sensors will remove all stack plots from the screen good for getting rid of your plotted profile e Zoom in Stack Profile allows you to increase the scale of the magnetometer readings the positions will remain the same but the variations in the readings will be easier to see You can also press the key to do this e Zoom out Stack Profile allows you to decrease the scale of the magnetometer readings You can also press the key to zoom out In the case of the above survey there is one sensor so we choose P ot Sensors Setup We need to select the single sensor 98 Plot Sensors Setup Sensor 2 Pseudo Gradient 2 1 Use Chl and Mouse to Select Multiple Sensors Plot Sensors Setup menu with single sensor selected If we instead choose the option Phot AU sensors Magmap will attempt to graph all the sensor readings on a single scale e g the first sensor has readings averaging around 50000 gamma whereas the second non existent sensor has readings that are 0 As a result it will be difficult to see any small features on the stack profile since
147. our survey such as invalid line or mark spacing In the Sensor type combo box choose the configuration of your sensor s 12 1 1 1 0NE SENSOR 1 OR LEFT OR TOP OR FRONT You had one sensor only and it was connected to the first connector 12 1 1 2 0NE SENSOR 2 OR RIGHT OR BOTTOM OR BACK You had one sensor only and it was connected to the second connector 12 1 1 3 HORIZONTAL GRADIENT RIGHT LEFT WHEN WALKING ACCORDING TO FORWARD DIRECTION You had two sensors second sensor on the right of the first sensor 168 You want the horizontal gradient with the Jeff sensor magnetic field subtracted from the right sensor magnetic field when you walked according to the picture defined in FORWARD DIRECTION For example if you set the FORWARD DIRECTION to the first item line going up in the increasing Y direction Every sutvey line going in that direction will have the gradient computed as the following right left Every survey line going in the opposite direction will have the gradient computed as the following right 12 1 1 4 HORIZONTAL GRADIENT LEFT RIGHT WHEN WALKING ACCORDING TO FORWARD DIRECTION You had two sensors second sensor on the right of the first sensor You want the horizontal gradient with the right sensor magnetic field subtracted from Jeft sensor magnetic field when you walked according to the picture defined in FORWARD DIRECTION For example if you set the FORWAR
148. plotted Shown below is an example of the Print Preview screen Next Page Prev Page Twa Page oom In Close maiie g d eL ee ed oe You can also choose the type of printer you want to use and the parameters by selecting Print setup from the file menu We recommend that you use a landscape paper orientation The printers available are set up using the standard Windows printer setup You can get your hard copy by pressing Prin 177 15 Example Manipulating a Survey with a csv file The option G 858 bin files and csv file currently supports files that are created from Trimble s Pathfinder software The csv file is a file that has differentially corrected positions that were produced from the Pathfinder program The 858 binary file should have GPGGA data strings recorded as serial data and there should be a one to one correspondence between readings in the csv file and GPGGA strings in the binary file This section describes the operations you need to go through to load these files and some basic data operations you can do with this 15 1 Load the files To load the files you need to select Open This should give you the following menu Open Look in EX csv a line gen czv sampocsv bin File name sampcsv bin lime gen csv Files of type G 858 bin files amp csv file Cancel Make sure that 1 You select files of type G
149. position you specify using previous positions of the boat to give a more accurate boat positions Typically this is not used in land surveys e If you select this option make sure that you don t include your cable length when you specify your distance Y E g If you have a single 880 magnetometer that you tow with fifty meters of cable you should specify a dragging distance of 50 and a Y offset of 0 assuming that the GPS 15 located at your tow point at the rear of the vessel If your GPS is not at the same position as the tow point you would enter the Y offset for the GPS with respect to the tow point e Add This will add a position point to the list It will use the current parameters filled in under X Y Z and Name e Delete This will delete the selected position point from the list Note You cannot edit a position point once it has been created If you want to modify an existing position point select it delete 1t and type in your correct offsets Then press 8 5 Smoothing positions Magmap uses a smoothing spline of the third degree to smooth data 140 This feature allows you to smooth your GPS data and get rid of spikes in your position After selecting the menu option 500 0 positions you should see a menu such as the one below that lists all of the lines you have in your survey You will also see series of parameters you can set to manipulate the magnitude and type of smoothing We will star
150. r to your line Usually the default works well in this case 124 e Iterations This is the number of times the program will increase decrease the iteration step e Iteration step this is amount the program will try to vary the field for a particular line on a given iteration e Max change This is the maximum magnetic field amount that a line will be changed The two parameters iterations and iteration step are best explained by understanding the method by which the destriping routine works During the destriping process we compare the readings across a number of lines that are taken perpendicular to the direction of travel If we compare all the magnetic readings across a given perpendicular line there will be a point on a survey line at which a minimum value occurs and a point on a survey line at which a maximum value occurs For each survey line we make a total of all the minimums and maximums occurring on a perpendicular line In destriping usually one or more lines will have an abnormal amount of maximums and another one will have an abnormal amount of minimums By changing the field values of each line by a small constant value we try to have an even distribution of maximums and minimums for each line and hence destripe the data We take small steps iteration steps because we don t want to overshoot e g add too much to a minimum or subtract too much from a maximum but we also need to take enough steps to make a
151. range of data and some smaller anomalies will not show up when graphed If we do a shaded relief plot using the magnetometer data we get 20 00 100 Sm Surfer shaded relief plot of magnetometer data 100 00 127100 14000 Here we used e X X e Y Mag Y e Z DIURNAL 3 We can also see several anomalies from looking at the map There is a long pipe that runs across the top of the screen and another pipe that connects and runs parallel to the Y axis X 40 Also note that these coordinates are graphed using the offsets we specified in the UTM screen We can compare this plot with one we obtain using the non shifted positions replace mag_X and mag_Y with GPS_X and GPS_Y 20 00 40 00 60 00 80 00 100 00 120 00 140 00 Surfer shaded relief plot with uncorrected positions As you can see here we can see errors introduced because the magnetometer and the GPS are not in the same place We can also look at the data that has not been diurnally corrected but the positions have been corrected 14000 A 17000 4 10000 e o ot 1 T YE EIE Tu 2 Data with no diurnal corrections 215 18 G 858 Survey with no GPS data Magnetometer surveys were typically done using a pre defined measured grid that would allow the surveyor to establish a few position points and time interpolate the rest Recent developments have allowed the
152. raph and then zoom in on the lower left hand corner corresponding to the coordinate 0 0 Both examples show the initial shot and two additional shots corresponding to two successive zooms The first example deals with automatic scaling When you look at all three shots notice that the number of scale lines never changes 104 72 100 bin 7 72_100 bin Same map zooming in on 0 0 once 72 100 bin Same map zooming in on 0 0 twice 105 From here we can observe that the number of white grid lines always remains the same no matter how many times we zoom The spacing between the grid lines does change This is different when we manually scale The parameters are shown below Set coordinate grid parameters Ed AMS Iv Draw grid lines Auto grid interval step Decimals s anis v Draw grid lines Auto grid interval 1o Decimals Choose Font Cancel The initial graph we obtain follows 72_100 bin Initial graph using manual grid lines 106 72_100 bin Graph obtained from zooming in on 0 0 ereen starting square If we zoom in again we see the lines again change Graph obtained from zooming in on 0 0 twice Note As one can see the total number of lines always remains the same when there is a manual scale grid is fixed and the number of lines shown on a given view remains the same when there is an automatic scale
153. rdingly There is a maximum of 300 grid points in a given direction One important tip to remember is that it will take longer to generate the graph if you select more grid points However the resolution might be better if you have more grid points in the direction you took your measurements Faster computers are always better for tasks such as these 92 5 1 4 User Interactions for 2D 3D plot In 2D 3D plot user can rotate translate scale and zoom the graph The procedure for each operation is explained as follows e Rotation 3D only 9 Hold down BOTH mouse buttons and either Q Move mouse counterclockwise to rotate view clockwise Of Press x z ot e to select an axis and then move mouse perpendicular to axis Note Some mouse drivers interfere with these dual button controls e Translation 2D 3D Press SHIFT and hold down BOTH mouse buttons 9 Move mouse to shift the chart e Scaling 2D 3D Press CTRL and hold down BOTH mouse buttons 9 Move mouse down to zoom in or move mouse up to zoom out e Zooming 2D 3D Press CTRL and hold down LEFT mouse button Move mouse to select the area to zoom into e Return to Default 2D 3D Q Press r 1 scaling translation and zooming removed Moving mouse cursor insider the contour surface map will display the line number LN mark number MK x and y coordinates representative date time grid value FIELD and representative reading number of the closest gr
154. re smoothing The user should try different values by pressing the Preview button and examining the results as it is shown on example below The black line represents a preview of the smoothed values Note that the minimum amount of smoothing that gives a reasonable result should be used Employing too high a smoothing factor will tend to remove small micropulsations and other rapid field variations that may be real Some experimentation will be required to get a good result but in general a spline degree setting of 5 to 10 will be sufficient 114 After a satisfactory result has been reached the Smooth base station data dialog box should be recalled and the Accept button clicked The original base station readings are then replaced with the smoothed values Now the user can proceed with the field reading export as usual Smoothed base station data is used instead of original base station readings to perform diurnal correction Remove button erases results of smoothing from the plot without accepting them 6 3 Base station user interface description and symbols definition Magmap96 22 8 2 Va GI Figure 65 In the previous graph Figure 65 the Y axis represents the amplitude of the magnetic field in nT and the X axis the reading number The time of the first and last reading is shown on the X axes 115 When you move the mouse cursor in this window additional information will be shown o
155. removing spikes from your data 16 1 Layout of Survey This looks at the two sample files included 880Test txt and GPSTest txt These files were generated using a course with the following features 500 x 500 meter grid Survey is done in several bi directional continuous lines Line spacing is 25 meters Speed of the boat is 10 meters second Ratio of Magnetometer to GPS readings is 10 1 For the individual files Small positional and magnetometer errors are introduced Some drop outs and spikes also occur in magnetometer data Magnetometer gradiometer data is given one magnetometer is assumed to be 40 meters behind the boat and the second 1s assumed to be 50 meters behind the boat There are two magnetometer sensors each with depth and altitude channels similar to a G 880 Coordinates are given in geographical format 16 2 Importing the files We can directly import the files into Magmap by loading the associated survey file or by directly loading the individual files in this case You need to make sure that vou use one of the two options available in the open dialog y P g 182 Maglog projects Survey this is used to load a survey and all associated files Maglog files this is used to load individual Maglog NT files After this is done you should see your two files appear in Magmap as follows GPS Test txt tit LIT MN TTL OT m pe pe RUE pn
156. rm Fa Method Cancel Choose Remove median abs ch1 abs ch2y and press OK The data will be transformed and all of your views will be updated accordingly If you save your data now the transformed data will be saved If you want to undo this action go to Survey setup and choose Orginal Readings intact as shown in the dialog box below Metal mapper transform Method Original readings intact OF Cancel After you have pressed OK all data will be restored and views updated Note This option is not available if you load an ASCII stn file Hence you will not be able to reverse any changes once you save to a stn file and then load this file 149 10 Using Multi Telegram messages with MagMap2000 Some devices used during marine or airborne surveys can produce multi telegram messages Most common example is the GPS with its variety of NMEA strings Depending on GPS model and configuration it can produce GGA VTG GLL etc messages These messages could not be used with MagMap2000 in the past However newest software version allows handling of such devices Here we provide and example how GPS stream can be used to extract VTG messages and include results in the MagMap200 export output file It s important to understand that MagMap2000 uses prefix to select strings of interest If beginning of data string matches to the user provided prefix data is accepted or rejected depend
157. rotate the grid by 90 degrees at the origin X 0 and Y 0 you will obtain the picture in Figure 62 BREEBEBESESE BA BREEBSBEESE BA BREEBEBEESE BA BA z z Figure 62 4 6 4 Grid settings You can change the erid parameters that you already defined as described in paragraph 3 4 Defining the grid G 858 simple survey mode or G 856 only page 46 In the case of mapped sutvey mode you can redefine your grid This will change the coordinates of evety position acquired in your survey You should only use this feature if you set up invalid orid information in the G 858 magnetometer before doing your survey such as invalid line or mark spacings Potentially every position in the survey may be changed 4 6 5 Exporting the survey to Geosoft or Surfer See section 12 4 6 6 Plotting magnetic field readings of the entire survey For example if you plot all the readings of the survey in Figure 10 you will get the following picture 78 survey bin 2 Figure 63 For more information on this window see the section about plotting readings Section 0 page 116 Readings are not shown in their correct linear position only in the sequence that they were taken 4 7 MagMap2000 Coordinate Transformations This chapter discusses how MagMap2000 can transform a 858 local or GPS coordinate system into a different coordinate system using Pseudo Affine transformation and triangulation Ther
158. rregularities in 858 coordinates cannot be removed with this method Example 3 You have a known net of reference points In this case there is a net of points where both local 858 and State Plane coordinates are known Reference points may or may not coincide with Line marks See example below dom m m m an LIBISIIIIIIIIIIIIILIIIS e e o m o m mw me m h m he eS h n 1 Refence points Ho Spo Ru ee 858 lines The program computes the Affine Transform in each of the triangles X a xcta y c a Because the triangle defines a plane surface the corners of triangle reference points above will be computed with zero error However note that if the reference net is sparse then the curvature of the survey lines will not be taken into account If there are errors in the reference points the survey lines could be curved If the State plane coordinates are known for each start and stop mark of each line it is possible to obtain the transformation by defining only a few reference points Here is an example 1A 2A 1B 2B 3B 86 3A 4A 5A 5B 4B If it is known that line 3 positions are suspect you can use points 1A 1B 2A 2B 3B 4A 4B 5A 5A A good result will not be achieved using points 1A 1B 3A 3B 5A 5B MagMap2000 implements this function the same way as in replacement of all marks Select Survey Setup Coordi
159. rvey Since you have already described your survey to the G 858 data will be located using the information you entered during the survey Note You are able to edit and reposition data in both simple survey and mapped survey modes Simple survey requires some positioning information to be entered In mapped survey the positioning information 15 entered in the field and you will most likely not need to edit any positions or enter any further information 26 2 How To Quickly Get Started This is section is intended for the user who wishes to quickly start downloading and editing G 856 or G 858 survey Much more detail about the various functions is given in later sections Please read those sections for more useful information about the capabilities of this program when you have time 2 1 How to download your surveys Click the left mouse button on the toolbar button labeled Import or select File then Import in the menu You will need to select whether you have a G 858 or G 856 2 2 How to edit positions 2 2 1 Selecting and editing a single position To edit a single position click the right mouse button right click on the position symbol small blue square You can select more than one position by pressing CTRL and clicking the left mouse button on each position you wish to select Then right click to bring up the editing menu To move the position to a new location select Move Positio
160. s Selecting Plot Mag Field in 2D Contours and Plot Mag Field in 3D Surface will give a 2D contour plot and 3D surface plot respectively If this is done from the survey map both plots use the current number of lines as X grids and a fixed 100 Y erids to create the mesh points If this is done from the GPS map both plots create a fixed 100 x 100 mesh points The grid value Z is interpolated by two magnetic field readings that are closest to the grid point The following pictures are the 2D 3D examples for the survey on Stanford Test site 88 fn Plotting Mag Field in 20 Contours for Sensor 1 2D Contour Plot etnia Bir Plotting Mag Field in 30 Surface for Sensor 1 3D Surface Plot By default it will create 10 contour levels using maximum and minimum grid values The value and color represented at each level are listed to the right These plots use non offset GPS antenna to sensor coordinates In order to get a plot that takes offsets heading error removal or de striping operations into account you will need to export the file and then either view the output in a plotting program such as Surfer or reload the file as a Surfer dot file into Magmap 2000 89 Note You can choose to plot any sensor or pseudo gradient if available by right clicking on the map and selecting the option Plot sensors setup You can then choose the sensor you wish to plot 5 1 2 Equalizing co
161. s To see how the prime meridian affects the generated graph you could try setting different prime meridians and seeing how your map changes 8 6 3 Cannot get origin of grid to correspond to 0 0 This could happen if you start with non zero offsets The easiest way to make the bottom left hand corner of your screen correspond to the point 0 0 is to In UTM setup set your northing and easting offsets to 0 Press On your GPS map look for the two numbers on the bottom left of your screen and write them down e g 500000 00 6000000 00 Then go into your UTM setup again and input the negative of the first number for your northing parameter and enter the negative of the second number for your easting parameter In the above case I would use northing 500000 easting 6000000 Press to accept the changes Your data should now be drawn correctly 147 9 Other devices 9 1 Metal Mapper The metal mapper is a device which can be connected to a G 858 console instead of the magnetic sensor From a technical point of view there is no difference between data collected with a true magnetic sensor and data collected with an EM device this means that Magmap will not be able to distinguish between the two different types of data and it is up to the user to tell the program what to do However this data should be treated differently 9 1 1 Opening a Metal mapper data file To tell Magmap how to
162. s selected as X position Y position is selected as 2 mag Y For latitude and longitude data the check box below must be checked For UTM local coordinate systems do not check this box NOTE If the data is Lat Long you MUST check the box or your resultant map will show no positions green screen one red and one green position box nothing more e Time information To display data correctly MagMap needs time and date information It is looking for key words time and date in the file header and will automatically select them However you can always select other columns as appropriate For a data file without time information date and time values will be generated internally because MagMap needs these values to be able display the data in a linear fashion Check File 42 has no time stamps assign time by default box to use default time stamps Keep in mind that in this case the time displayed by MagMap is synthetic and so no time related operations like base station correction can be used e Time format MagMap can load dates in the following formats o US time format as Month Day Year Fields are typically separated by forward slash year has short notation like 07 stands for 2007 o European time format The same as US but day goes first o INTERMAGNET date format as YYYY MM DD Here is four digit year is followed by dash and two digit month and then dash and two digit day Example is 2007 09 11
163. same type open at one time You should also check and make sure you have the map rather than the base station file selected 17 5 2 Concatenating two files In this example we took data in two files and exported into two separate files However we still would like to look at all the data in one map We can choose to combine these files either in Surfer refer to Surfer documentation or do it through DOS To do it through DOS you need to do the following steps 1 Remove the heading from your second file This is important because Surfer recognizes headings only from the first line e You can do this easily from a text editor by deleting the first line 2 Concatenate the two files with a command at the DOS prompt such as Copyatb c e a and b are your first and second files and is the name of the new output file In this case we named our two output files 0 70 dat and 72 100 dat We wanted to output to a file called 0 100 dat so we typed Copy 0 70 dat 72 100 dat 0 100 dat 213 These two steps are all that is necessary to concatenate a file for use in Surfer 17 6 Analysis in Surfer This section assumes you ate familiar with basic operations in Surfer If you are not consult the Surfer manual for discussions on the plots used We find the shaded relief plot to provide the most useful view of our data The contour plot doesn t work as well here because we have a large
164. se station data with a spline filter It is possible in some cases for the base station data to have more noise than the field magnetometer A typical example would be the use of the proton G 856 magnetometer as a base station and the cesium G 858 magnetometer as the field sensor The G 856 has a typical noise envelope of about 0 25 nT and G 858 has a typical peak to peak noise of 0 1 nT Thus applying base station correction in this case can reduce the final precision of the corrected field data Smoothing of the base station data with third degree spline filter before applying the diurnal correction routine can alleviate this problem Replacing the original base station readings with their continuous equivalent effectively moves the noise into a very low frequency domain In this manner local magnetic anomalies are not distorted with noisy base station readings It is recommended that the user despike the data prior to using the spline smoothing filter This option is available under Filter Smooth base station readings menu 113 Scale Baza Plot Setup Window Help j Despike ee Linearly Interpolate Drop Outs Remove Drop Outs Despike Setup Smooth base station readings After this option is selected the following dialog appears on the screen Smooth base station data Smoothing degree 10 ok T Accept Remove Cancel A larger smoothing degree value provides mo
165. ss may be required to remove the data spikes Using the number of readings identified in the first part of the investigation process above and using the maximum amplitude of the spike are good values with which to start If the application of the spike filter has no effect on the profile plot then a larger number of readings and or a lower maximum anomaly level may have to be applied Just click UNDO to remove the last spike edit process and then apply the new parameters When spike editing keep in mind that all data will be edited that meet the criteria not just the anomaly you are investigating Sometimes removing the largest very sharp anomalies can enhance your ability to see smaller objects in the survey area The process of removing spikes is discussed in more detail later this chapter 7 3 Removing drop outs Drop outs occur when the magnetometer is in a dead zone or near a very large iron or steel object like a cat They show up as zero readings in the data stream They can be removed by selecting Remove Drop outs Lanearly Interbolate Drop outs from the Filter menu This should always be the first operation erformed on new data The process can be reversed by selecting for example EDIT undo removal of drop outs Remove Drop Outs will automatically delete those readings with exactly zero value and adjacent readings around those zero values one reading This will cause no 1D plotting for those readings
166. ssing 18 2 Manipulating the G 858 data Now that we have edited the map we should look at the data and check for drop outs and spikes Note The magnetometer data associated with the GPS and the magnetometer data associated with the map are treated separately Any changes e g despiking removing drop outs that are done to one data set are not applied to the other 221 You can look at the G 858 data by positioning the cursor on a point that is not the endpoint of a line e g in this case we positioned it on one of the black lines with arrows Right click on it and you should get the menu seen below Shift Grd Reverse Grid Rotate Grid Grid Setting BERNERENREREEEENE Hs m b el od ool ield Id in 20 Contours Plot Field in 30 Surface Plot Stack Profle Un Top Of Map gt After selecting Plot Mag Field you should see the following magnetometer data Plotting of readings from Line 0 mark ll to line 37 mark 1 50510 357 0 000 11 26 36 600 13 04 40 300 Magnetometer data The discussion of how to remove drop outs and despike this data is given in section 0 above 222 18 3 The base station data The base station data is treated the same as in the previous chapter section 0 above 18 4 Analysis of G 858 data from within Magmap This section describes some operations commonly used in analysis 18 4 1 Setting a proper scale We can use Magmap to gauge how
167. stics file will report the statistical variance and the maximum offsets of the destriping process Enter file names Enter name of input file file IE should be space separated column file With v coordinates of data points field values and possibly line numbers E Frapjecks sM anualas agmapsb E ample Files SB E am Browse Enter output fle name IF exists will be overwritten Holds s v Field output da Brawse Enter file name for statistics of destrping if needed stat dat Browse Output statistics file Cancel File name dialog box 7 5 2 2 INPUT FILE PARAMETERS DIALOG This screen allows you to specify how to read the input file Since destriping uses a columnar approach to interpreting the data format you need to tell the program which columns hold the pertinent data Usually the X and Y columns are listed as well as one of the magnetometer or other data file columns and the line number column If you have collected multiple sensor data then you will have the option of destriping either sensor or the gradient columns 122 Input file parameters Data File E Prajects M anualz M agmapSE E xample Files 8046 Output File output dat column Y column 2 maY O Field column 3 ma2x oO ej Line column if exists ma Y A Use distance interval to split the lines Back Cancel Input file parameters screen By default the X Y Field and line columns
168. stimated as the value of the longitude but you should look it up below for a better calculation of your positions 135 The Universal Transverse Mercator UTM Coordinate System uses zone codes instead of specific projection parameters The table that follows lists UTM zone codes as used by GCTPc Projection Transformation Package Zone C M Range Zone C M Range Ol 177W 180W 174W 31 003E 000E 006E 02 17IW 174W 168W 32 009E 006E 012E 165W 168W 162W 33 015 012 018 4 159W 162W 156W 34 021E 018E 024E 05 153W 156W 150W 35 027E 024E 030E 06 147W 150W I44W 36 033E 030E 036E 07 141W 144W 138W 37 039E 036E 042E 08 135W 138W 132W 38 045E 042E 048E 090 129W 132W 120W 39 051E 048E 054E 10 123W 126W 120W 40 057E 054E 060E 11 117W 120W 1I4W 41 063E 060E 066E 12 111W 114W 108W 42 069E 066E 072E 13 105W 108W 102W 43 075E 072E 078E 14 099W 102W 096W 44 081E 078E 084E 15 093W 096W 090W 45 087E 084E 090E 16 087W 090W 084W 46 093E 090E 096E 17 081IW 084W 078W 47 099E 096E 102E 18 075W 078W 072W 48 105E 102E 108E 19 069W 072W 066W 49 111E 108 114 20 063W 066W 060W 50 117 114 120 21 O57W 060W 054W 51 123E 120E 126E 22 051W 054W 048W 52 129E 126E 132E 23 045W 048W 042W 53 135E 132E 138E 24 039W 042W 036W 54 141E 138E 144E 25 033W 036W 030W 55 I47E 144 150 26 O27W 030W 024W 56 153 150 156 27 O21W 024W 018W 57 159E 156 162 28 015W O18W 012W 58 165E 162E 168E 20 009W 012W 006W 59 171 168
169. t the destriping routine and with the destriping routine run once Note that the stripes on the original data are much more pronounced 127 E Shaded relief after one pass Destriping higher amplitude Original Data at higher amplitude Shown below is data taken after destriping has been done twice eee m a a nn m a a m a a a m o nn mn as ta at higher amplitud 129 7 6 Pseudo gradient During loading of G 858 compressed or ASCII files Magmap computes a psuedo gradient the difference between sensors one and two This appears in the program as a third sensor e g a G 858 magnetometer would appear to have three sensors as opposed to two All kinds of processing available for total magnetic field are therefore available for the pseudo gradient including 2D and 3D maps line graphs and stack profiles For example the plot selection plot sensors setup dialog looks like the following Plot Sensors Setup Sensor 2 Pseudo Gradient 2 1 Use Chl Rey and Mouse to Select Multiple Sensors Cancel This pseudo gradient option is also available when selecting what to plot for the contour plot and the 3D plot Contour map after one pass Destriping Original contoured data 131 Shaded relief after one pass Destriping higher amplitude Original Data at higher amplitude 132 8 GPS 8 1 Overview Magmap will only import GPS data that has been stored with the f
170. t the same rate as the magnetometer This means that there will be a base station reading that corresponds to every roving magnetometer reading In this case the diurnally corrected reading can be calculated by the following formula DiurnalReading t RovingMag t BaseStation t Where each reading is taken at a given time 1 In other cases where fewer base station readings are taken Magmap will linearly time interpolate between known readings for the intermediate readings The diurnally corrected reading will then be calculated in much the same way as above 111 Note In cases where the two magnetometers are not set to the same time you can add a given time to the base station clock to make it correspond to the roving magnetometer clock If you do not have a proper base station file open Magmap will inform you of this at export time You will see the message No valid base station files are open This message will not appear if you have a valid base station file open e g a base station file where the roving magnetometer and base station times overlap The quality of the correction may be degraded by a mismatch in times between the base station and survey data a time mismatch combined with highly variable base station data and noisy or spiky base station data Although it is optimal to synchronize the instrument clocks and place the base station in a magnetically quiet location for the survey this is not always logist
171. t with the sample GPS screen below Magmap 2 Survey GPS_gps up STATA E 8 S LT 3 oe eg D A Ly TTA AP TAT LULL cu Lad mm oe oL LELES D When we pull up the smoothing menu we get the following Line smoothing parameters setup fe fe fe fe fe 4 5 apply This dialog box gives us a lot of information It lists all of the lines has identified and allows you to set individual smoothing parameters for each line You can click on any of the parameters except for Line 2 and change the value The parameters 141 e Line this is the number of the line you will be smoothing e Spl Smooth 1 This gives you the option of turning smoothing on or off for a given line e Parameter This controls the degree of smoothing e Despike This allows you to choose whether you would like to despike before smoothing or not e Jump This controls the distance that is considered a spike program will calculate a smoothing curve It will then calculate the distance between these smoothed points and your original points If any of these distances are greater than the distance you specified in jump the point will be replaced by the point on the smoothed curve All other points falling within the jump distance of the smoothed curve will be left a
172. te click on the YES button otherwise click on the NO button to abort 958 continuous survey mode Deleting a position does not delete the magnetic field readings acquired during the survey If a position is deleted magnetic field readings are linearly interpolated between the previous and next position of the deleted position For example in the survey plotted in Figure 10 if you delete the position at MARK 1 LINE 0 located at X 0 Y 100 you will obtain the picture in Figure 16 54 Figure 16 G 858 discrete mode or G 856 Deleting a position does delete the position and the corresponding magnetic field acquired at that location 4 3 Selecting and editing entire lines To select a line right click the mouse button on the start of line symbol big green square or on the end of line symbol big red square A pop up menu should now appear on the screen Figure 17 e To shift the line by an X or Y offset select Shift Line By To reverse the direction of a line select Reverse Line To correct a walking deviation error for example you did not walk straight and end up at another line select Add Line Deviation e To rotate a line select Rotate Line e To move only the start of line or end of line position select Move Position To e To plot every magnetic field reading of this line select Plot Mag Field To delete a line select Delete Line Once you have select
173. the computer For example one could interpolate fluxgate magnetometer data acquired during an airborne survey to the main cesium magnetometer times This interpolated data set could then be used for Compensation processing This feature cannot be used for binary data Pressing the Next Button brings up the following screen Additional data files to interpolate EJ Additional data files to interpolate Channel numbers Channel names Pretix F dataTimblossystest dat 1 2 Rotation Heading Add data file Remove data fileja Output digits after dot 2 lt Back Cancel ere is no need to interpolate addition es sim fess ext to advance to the nex If th d to interpolate additional files simply press Next to ad to th t screen 162 The middle of the dialog box is initially blank Files are added by clicking on Add data file and removed by using the Remove data file s button Press Add data file button to add new data file to the list First a standard Open file dialog appears where the name of an existing file will be selected Then a second dialog box appears where fields in the file will be specified Specify channels amp names Additio it Data file X Ad FsdatasTimbilossy stest dat E File beginning 0 159 0 531 11 03 01 09 58 01 515 0 318 1 062 11209201 09 58 01 595 0 476 1 592 11209201 09 58 01 655 0 637 2 122 11 03 01 09 58 01 735
174. these offsets our map should appear as follows gem Ld r mz 732 T p p e mn E p p n m A rm o p T _ OT GPS map in local coordinate system 17 3 4 3 COMPUTING ADDITIONAL POSITIONS Now we need to add a position point for the magnetometer As said before the GPS is located about 1 6 meters behind the magnetometer As a result if we were to graph the data we would see many errors due to the fact that the GPS and magnetometer were not at the same place These errors would also depend on what direction we were travelling while taking the data In lines going up the magnetometer would appear to be ahead of the GPS and we would need to add 1 6 meters to each GPS position in order to make this appear correct In lines going down we would need to subtract 1 6 meters from each GPS position in order to get the correct magnetometer position A single anomaly would appear to be in different places from line to line 205 Magmap can correct for this by outputting an extra position point See Chapter 7 for more discussion We would like to have two position points outputted one labeled GPS and one labeled Magnetometer We can do this by selecting the GPS menu and then selecting GPS Offset From here press Multiple Offsets Setup Then fill out the dialog box as follows Multiple Positions Se
175. thing and turned the second smoothing with the parameter to four After pressing OK the changes are reflected in the dialog box To smooth the data we press 500 7 This should draw a series of yellow lines that will show what your smoothed data will look like if you apply the changes Note No changes will be applied until you press Close and Apply If you don t like the results of your smoothing you can exit the screen by pressing Close or you can change the smoothing parameters and press Smooth again For the example data shown before pressing 5200 7 results in the following screen 143 As you can see line four fifth from left appears straighter than the other lines because it has a higher smoothing parameter and the second degree of smoothing is turned on If we press Close and Apply the changes are permanently applied Once applied these changes cannot be undone You will have to reload your file if you want to undo your changes The smoothed data is shown below Magmap 2 Survey GPS_gps OE XI 144 8 5 1 Recommended Smoothing Procedure We recommend the following for optimum results 1 2 3 4 Turn off despiking and your second smoothing Figure out your first smoothing parameter by trying lower numbers first and higher numbers later You want your smoothing to be strong enough to minimize any effects of spikes From here there are two things you need to
176. tions twice and this should not affect any attempts to graph the data However we still need to delete the last part of the line where the data could be bad due to the loss of battery power To do this we select the end of the line and then right click on the mouse as shown below In this case there two bad segments to delete When you have finished deleting the bad segments your final map should look like the following Note The sample file 0 70 bin was improperly terminated and can cause problems during export If you have problems exporting this file reload the GPS file and don t delete the lines above 202 GPS map with segments deleted 17 3 4 2 CHANGING TO UTM COORDINATES We intend to later import this data into Surfer so it would be helpful to have the coordinate system in a more manageable format UTM To do this we need to first display the UTM coordinates with no offsets and then change it into a local grid that has some more manageable numbers We can change to UTM by selecting our GPS menu Make sure that your GPS screen is the active one otherwise you will not be able to find this menu From here select UTM Setup We Ae map usna Ere Gh a T ETT Tia C Suey pE mUuL n F Fo oF Lr mew map TETTE ama tne leae aimag ogia suren UTM setup Then fill out the parameters
177. to eliminate the obvious spikes Despike Next we do a quick spline fit for REVIEW using Smooth Readings dialog box under Filter If we wish we can do some additional despiking after applying the filter to see the results Channels ta applu Pseudo Gradient 2 1 1 L Deselect all Select all Cancel Accept difference ter Review again from the Filter dialog and see results And now apply a factor 3 spline fil 14 Smoothing deqree E E Channels to apply Preview Accept difference 4 220 350 1BO 16 140 120 1Q 606 4g 2 Ctri left mouse drag to Zoom Press r to reset For more information please refer to the manual and visit our website often for more updates Table of Contents 1 WHAT IS MAGMAP 23 1 1 PROGRAM FLOW OVERVIEW 23 1 1 1 DOWNLOADING DATA FROM THE G 858 24 1 1 2 PC FILE FORMATS 24 1 1 3 ACCURATELY POSITIONING DATA 24 1 2 REQUIREMENTS 24 1 3 INSTALLATION 25 1 4 USAGE 25 1 4 1 BASE STATION 25 1 4 2 SIMPLE SURVEY 26 1 4 3 MAPPED SURVEY 26 2 HOW TO QUICKLY GET STARTED 27 2 1 HOW TO DOWNLOAD YOUR SURVEYS 27 2 2 HOW TO EDIT POSITIONS 27 2 215 SELECTING AND EDITING SINGLE POSITION 27 2 2 SELECTING AND EDITING ENTIRE LINES 27 2 2 3 SELECTING AND EDITING SEGMENTS 28 2 2 4 SELECTING AND EDITING THE SURVEY GRID 28 2 2 95 SELECTING AND EDITING A GROUP OF POSITIONS 28 2 3 HOW TO
178. to smooth the data We can do this by selecting 5700 7 Position from the GPS menu We Aen mam WEG daa one TES D ET DEDIT EST He map SiG mas ana Db TEST EE GITE EDIT ES Smooth position We then see the following dialog Line smoothing parameters setup ip ae ELA Hose Since this data was done as line we only see one set of parameters we can change this may be different for Maglog surveys taken using several lines If we accept the parameters as shown we get the following 193 lel ES lOl x 505 01 505 01 gm m D bagues dei E ue pee pease ae as aca a mmnm mas Tema mema Nm me a tess T gt LITTLE m Fei Se HHHH 8 MAL So mal a meta ere SS SS ee SS me m mo HE Pe Plotting of map using GPS Sb SS rene P E Plotting of map using GPS oe E I BEN EE TTE H e mm m NR RN a BH l SSS m SSSR T DIR a ESE B m AMEMERBENEENEEEEN um TS m m 1 n r HELM I B PST est Ext 510 43 0 00 0 00 We accept this s
179. ton or pressed the ENTER key For example in the survey plotted in Figure 50 if you shift by X 10 and Y 0 all the selected positions you will obtain the picture in Figure 51 m m m gm gm gH g m m NM nmmmummummi ie ie ee me ee m m m m gm gm mg m m NN Figure 50 a m m m m mg gm gm mM R Im 9 m m m I 9 m m m m m m m gm m m NM NM et ee ee Figure 51 4 5 2 2 DELETING A GROUP OF POSITIONS For example in the survey plotted in Figure 50 if you deleted every selected position you will obtain the picture in Figure 52 m m m m m m mg m gm m9 NM M NM g ey a Figure 52 The behavior of the program differs depending upon whether you have performed a continuous or discrete survey G 656 continuous survey mode Deleting a group of positions does not delete any magnetic field readings acquired during the survey If a group of positions is deleted magnetic field readings are linearly interpolated between the previous and next positions outside of the selected group of positions End of Line and Start of Line positions can not be deleted 958 discrete mode or G 8 56 Deleting a group of positions does delete every position and the corresponding magnetic field acquired at their location End of Line and Start of Line positions can be deleted 4 5 2 3 LININ
180. tup GPS clock bias in secs o Cancel From here press Multiple offsets setup 195 This will give you the following menu Multiple Positions Setup z 0 Name magl Add Delete Iw Use dragging Dragging distance m 45 Recall that we have two magnetometers one is dragged 40 meters behind the boat and the second is dragged 50 meters behind the boat In the above dialog box we have specified a dragging distance between the two magnetometers 45 meters and we have specified two positions we would like to calculate with relation to this dragging distance mag1 and mag2 You have the opportunity to export these positions and use them in gridding programs such as Surfer Note These positions are calculated later They are not available from within Magmap 16 5 2 Exporting to a file We have now smoothed and despiked our data We would like to export it so that we can make a orid in a 3D plotting program such as Surfer 196 To do this select Export You should see the following dialog box File Format Surfer Select Fields to Export dx 5 00 dy 0 00 drag dist 45 00 a SEEE A A PR E E nag z h 00 dizi D drag dizt 45 00 Export Data Separately to Detault File Names runs dv 5 00 dy 0 00 dist 45 00 nage Y dx 5 00 du 0 00 drag dizt 45 00 Select Output Path File Name Ense 7 Caen 00 du 0 00 drag 0 1 49 00
181. tup 0 00 0 00 0 00 Z Eoo Name GPS Add Delete Use dragging Dragging distance m There are a few important points to make sure you do 1 Make sure Use Dragging is disabled This is mainly used in marine surveys where the distance can be variable 2 Delete the initial position point you cannot edit and existing position point 3 Add the two position points labeled magnetometer and GPS After you have finished you ate done with what you need to do with the GPS data for this file It is useful to save your work Note The GPS position is included so that we can output our original positions and compare the results later It is not usually necessary to keep this position 206 17 3 5 Editing Magnetometer data that goes with the GPS We also need to edit our magnetometer data that will be used with the GPS As seen earlier we had data with drop outs Initial magnetometer data The first thing that we can do is to remove the drop outs We will choose to linearly interpolate the drop outs with good readings see Chapter 6 for more of a discussion on filtering data To remove the drop outs make sure that the magnetometer screen is selected Then from your Filter menu select Linearly Interpolate Drop Outs Despike Linearly Interpalate Drop Outs Remove Drop Outs Despike Setup Your new magnetometer screen should re scale to reflect the filtered data
182. umed to be comment line and is omitted e X Y scale factors Multiply positions by these numbers while reading the data e Data scale factor the same as above but for data fields All data fields are multiplied by this coefficient while reading from the files e Field separator Describes how data columns are separated in the file Possible values are SPACE and COMMA or SPACE In latter case either space or comma are considered to separate fields The beginning of the data file in shown in the right pane Here is an example how INTERMAGNET IAGA 2002 format can be loaded using the MagMap advanced features International Real time Magnetic Observatory Network INTERMAGNET data is available from http www intermagnet org Welcom_e html see Conditions of use on INTERMAGNET web site Note that data is recorded in UTC time 45 Advanced import X Import parameters File sample Header lines 464 2002 Source of Data United States G Station Mame Honolulu l4G 4 CODE HON Geodetic Latitude 21 300 Geodetic Longitude 202 000 Comment characters he a scale Factor fh nee Y scale factor Elevation Reported HLF Sensor Onentation Digital 5 ampling a H Data scale factor Field separator SPACE Cancel Here the program skips the first 12 lines in addition each line starting with is considered to be a comment 3 3 12 Showing all files T
183. use button on the direction symbol arrow located between the two positions then select Plot Mag Field e To plot a profile of only the readings for a specific line right click the mouse button on the red or green square of the corresponding line then select Plot Mag Field e To plot a profile of the readings for the whole survey right click the mouse button on the green area of the map then select Plot Mag Field Individual anomalies may be flagged using the right mouse click Select fag dentifier flag will appear on position and contour maps 2 6 How to create a 2D contour map of the readings To plot a 2D contour map of the readings position your cursor on the map and press the right mouse button If you are trying to plot a contour map using GPS cootdinates you should right click on a starting or end point green or red square Then select Plot Mag Field in 2D contours Note The scale of the contour map is created by a technique called Color Equalization This technique represents each color as an equal amount on the map As a result it gives a good picture of anomalies when other linear scales would allow drop outs and spikes to distort the map 2 How tocreate a 3D map To plot a 2D contour map of the readings position your cursor on the map and press the right mouse button If you are trying to plot this map using GPS coordinates you should right click on a starting or end point green or re
184. use of GPS positioning but there are still many surveys done without GPS positioning The sample survey discussed in Chapter 12 had GPS positioning but we also had a mapped sutvey setup We will use the same files but will approach the analysis from a mapped survey perspective 18 1 1 Loading the file In this section we will manipulate the two magnetometer files to get the correct mapped information We begin by opening the file The file type is G 858 Binary File as shown below Open Look in E Wagl32 E File name 0 70 bin Files of type G 858 Compress Files bin Cancel Note This menu will default to the last file type you selected If you do not select G 858 Compress Files as shown above you will still get your data but you might not get your survey map You should get the following map 0 70_bin Ce er Initial map for first G 858 file 18 1 2 Manipulating the map Now we need to do some editing operations on the map This map has a few problems that need to be addressed 1 We need to take out a line at X 52 2 The last line is bad because the magnetometer battery was drained We need to delete this line We will start by deleting the line at X 52 To do this we need to select the three position segments and then right click to select Delete Selected Segment s as shown below You can select more than one position point by holding down CTRL Map with p
185. used Other parameters that you can change are e Points to look forward Magmap needs to establish the direction the ship or person is traveling This tells it how many points forward from the current point it should use to establish the direction of travel 138 e Points to look backward This tells Magmap how many points backward it should use to establish the direction of travel Note The number of points you use to calculate the heading can be very important We recommend that you choose between 2 and 5 points for both options If you are moving in a Straight line more points will tend to give a better answer If you are doing marine survey and making a lot of turns it 1s better to choose a small number of points e GPS clock bias This is a number that you would like added to your GPS clock time This is one way you can fix your positions if you have a constant offset In one case if the GPS is located 1 6 meters behind the magnetometer and we are walking at 1 m s we could use a GPS bias of 1 6 seconds to fix the positions Distance Velocity Time e Multiple Offsets setup This button allows you to set more position points The dialog box is shown below Multiple Positions Setup POSITION NAME 0 00 0 00 0 00 0 M ame POSITION Add Delete Use dragging Dragging distance m 0 From this dialog box you can add and delete extra position points to be calculated You can also specify whether to use
186. ution Our programmers have come up with a magnifying glass zoom tool like those found in graphics programs The Icon is a circle with a small box in it Simply select this icon and then draw a box around the portion of data that you want to zoom Menu bar for Zoom Tool When you have finished zooming and wish to return to the original coordinate display simply click on the green icon with the arrows pointing outward V The Problem Sometimes we may want to apply a frequency filter to our data that becomes a spatial frequency i e we are looking for something specific a source of a given size Or we may want to eliminate a certain high or low frequency component in the data so that we can more clearly see the targets of interest The Solution For instance let us say that we are interested in the geological signal because we are looking for magnetite concentrations associated with placer gold deposits However there are also magnetic materials right on the surface due to weathering of the host rock We can raise the sensor to look deeper essentially applying a low pass distance filter but we can also filter out the high frequencies in the following manner Bring in data with low and high frequency components and contour If it looks sufficiently low passed then accept the data and generate a contour map Compare with the raw data contour map above 10 18 20 30 AC BO B 70 8g 40 106 118 Or o
187. ver data This means that virtually any base station magnetometer can be used with MagMap to diurnally correct any other magnetometer data file Go to File Open dialog and select SURFER dat files Interpolator INT Text txt files as the file type Then select your file of interest and press Open The program makes no assumptions about the possible file format and therefore a Data file definition dialog is required Data file definition X Data file name E datas B5B stanford72 1 OU dat Position information S E s 2 Y Check here if represent longitude and latitude Time information Time r TIME e Date 5 DATE No time stamps assign by default Format US monthday year Line information Don t use lines all data in one line Linie E UNE o Split data file into lines by distance Split distance on Data channels x READING 1 Remove data zhanmel Remove all channels How to load Positions amp Data Use advanced settings Advanced Cancel Use this dialog to specify the type of data provided in the separate file columns MagMap uses the first file line header to name the data columns If there is no header information then the first line of data is used to define each column e Position information Specify the columns with position information For example 1 Mag X means that 1 column has name mag_X and i
188. y on one plot will enable the user to insert an offset to the base station files to enable leveling of the data upon export Use Advanced Settings This selection allows tuning of the data import routines This provides for removal of multi string headers from a data files or use of a special character denoting comment lines which the program will not load In addition you can scale the data while loading For instance in some systems a magnetic field value of 40000 000 nT could be recorded as 40000000 Note that all previous selections such as the information denoting position and data columns etc ate erased when this button 1s checked and the Advanced button becomes available When clicked it shows the following dialog Advanced import X Import parameters File sample Header lines Base station data file Operator EREMIM MAKIN Source POS 1 Number 27 FIELD GMC ST DATE TIME Comment characters lo 2 scale Factor 1 E Y scale factor Data scale Factor 0 001 Field separator SPACE 51501552 00028 80 10 28 05 10 11 61501525 00033 80 10 26 05 10 117 61501520 00032 80 10 28 05 10 11 6150142 00033 sd 10 28 05 1 k Cancel Here the following fields are available to the user e Header lines Number of lines of text to skip from the beginning of the file e Comment characters If strings begin with any of the characters in that field it is ass
189. you that if you wish to export your data with diurnal correction you must first open the base station file or files If you have a proper base station file open no message will be displayed and your data will be diurnally corrected 12 1 9 Survey boundary consideration In continuous survey mode when you export your magnetic readings to Surfer or Geosoft Analysis and Plotting Software the first reading coordinates will not necessarily have the same coordinates as the first position of a line and the last reading coordinates will not necessarily have the same coordinates as the last position of a line When you press the mark key at a the beginning of a line and walk along the line you will get a reading after a delay defined by your cycle time For example when you start a line at 0 and Y 0 and end a line at X 0 and Y 100 and the magnetometer cycle time is set to one second you will only get the reading only a second later and the magnetometer will automatically record readings every second By definition when you press the end of line key you stop recording and therefore you may or may not record the last reading at exactly X 0 and Y 100 12 2 Exporting a Maglog NT survey This export procedure covers the export menu you will get from e Maglog NT sea survey G 880 G 881 e Airborne survey e based survey where GPS was loaded using the option Draw new map using GPS and the features of a Maglog NT survey 12 2

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