GridMerge—merging - Intrepid Geophysics
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1. Select Base Grids Available Grids Selected Grids 1003 a NE 3 Cancel Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 36 Library Help Top 4 Back gt High Rank and Low Rank The Ranking of grids applies only to the Merge operations This is an important means for the user to control the quality of GridMerge s final merged output grid The goal in merging grids 1s to retain the maximum quality and resolution available in every portion of the final grid and so where a high quality detailed survey overlaps with a more regional survey the data used to generate the final grid would preferably be drawn from the detailed survey The lesser quality survey would only be used 1n an area where no other data were available GridMerge does automatically rank all grids to best achieve this goal By default erids are ranked in order of cell size and for a given cell size further ranked by the number of pixels contained in the grid Thus the default ranking is e High rank larger surveys with small cell size i e detailed data e Low rank surveys with larger original cell size typically regional surveys The user is able to override GridMerge s default ranking by specifically nominating high ranking and low ranking surveys The first listed of the high rank surveys will be on top The first listed of the low rank surve2. i Intrepid Gidmerge 3 6 release cut 114 static Grid Operation Help Specify Report File Load Options Save Options uit The GridMerge File menu has four simple choices Specify Report File allows the user to enter a filename to which GridMerge writes any processing reports See further notes in GridMerge report files The two options choices allow the user to save the current processing settings Save Options or to load in a file of processing parameters Load Options which may have been saved during some earlier processing session Use of INTREPID job files is also covered in Batch Processing Section GridMerge batch operation Use Quit to exit from GridMerge Grid Operation Menu Choices GridMerge s main processing choices are grouped together under the Grid Operation menu a Intrepid Grdmerge v3 6 release cut 114 static OFX Grid Operation Preprocess Grids gt Fy Prepare Boundary View of Grids Level Grids gt k Res ample Grids Menge Grids gt e Trim Grids Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 6 Library Help Top 4 Back gt PreProcess Grids provides some utility functions The user might use these to assist in planning a GridMerge job or to do some pre conditioning operations to the input grids prior to GridMerging them Si Intrepid Gridmerge
3. job file This file can then be edited taking advantage of additional capabilities that are currently not implemented in GridMerge s GUI interface Lines or parts of lines that are hashed are comments and are ignored from the onwards JOB To use GridMerge via INTREPID s batch processing capability execute gridmerge exe batch file job Do not use any spaces in the job file name Process Begin Name gridmerge Comments Intrepid Audit Stamp v3 5 Cut 110 11 5 2001 InputDirectory E test_data support gridmerge dnre stagel OutputDirectory E test_data support gridmerge dnre stage2 ReportFile gridMerge Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 38 Library Help Top 4 Back gt Other files or directories that may be optionally used OutputGrid my_new_special_ one ReferenceGrid my_special_ grid UncorrectedGridDirectory grids RAW CorrectedGridDirectory grids GOOD PolygonWindow clip _ poly Now for some of the line levelling fields ReferenceZfield test line data Z InputXfield test line_data East InputYfield test line_data North InputZfield test line_ data Z OutputZfield test line_data newZ ShiftAndScaleDataBase test line_data_scaled H HHH HH HH OH HF CH Parameters Begin Base Grids High Ranked Grids a b c Low Ranked Grids a b c Band 1 Choose one of the foll
4. Degree 1 or Degree N limits GridMerge reverts to a lower order polynomial eg 0 or 1st order along the corresponding axis This means that when specifying a higher order polynomial some care is needed in setting these limits if an overlap is small and there are too few data points the polynomial degree would be reduced anyway To allow a higher order polynomial to run it may be necessary to drop the limit Conversely using high order polynomials with low overlap limits are likely to produce difference surfaces that are unrealistic over those parts of the grids for which there are very few or no overlap points Batch only If Reject Outliers is turned on the surface is fitted in two passes The first pass surface is fitted and points which deviate from that fit by more than 3 standard deviations are discarded A second pass fit determines the final surface Select Base Grids Base Grids are grids that are not adjusted during the DC Shift Scale Then DC Shift and Surface Adjust operations Base grids essentially define a reference surface to which other grids are adjusted A primary use of this feature is when you have a regional grid covering the entire area that you are confident has a correct reference surface Specify it to be the base erid and allow all other grids to be adjusted to it Note The concept of Base Grids applies only to GridMerge s corrections operations and is not used in Merge Select Base Grids
5. E E a Level grids by fitting polynomial surfaces to overlap differences Program Control Report file gridMerge Input directory C a_DFA 2661_66_GridMerge mag_ merge _test grids dc_ sy Output directory C a_DFA 2661_66_GridMerge mag_merge_test qia Base grid selection 1 1063 a7 Step 3 Feather Merge Grids This operation reads input from a subdirectory of adjusted grids and Feather Merges them into a single merged output grid file Merge selects values from the various input grids to build a composite grid file The input grids can be ranked such that high ranked grids are used in preference to low ranked grids during the merging Feathering is a process which attempts to smooth out any sharp steps at the edges of grids such that the final grid file has no join artefacts ie a Seamless final grid file 1s produced a Intrepid Gridmerge 3 6 release cut 114 static File Eel Help Preprocess Grids gt F Level Grids gt d Merge Grids Merge Grids by Pasting eee je and Feather Grids Specify the input directory Normally some DC_Shift and Surface Adjustments will have been done previously and the saved outputs would be specified here as the input to Feather Merge See Specifying Input and Output Directories The output required for Feather Merge is simply a name for the final merged grid file Library Help Top 2012 Intrepid Geophysics q Back gt INTREPID Us
6. averaging passes are undertaken the default being 6 with the filter length being halved for each successive pass Thus using the default Filter Length 5000 metres and Number of Passes 6 filters with wavelengths of 5000 2500 1250 625 312 5 and 156 25 metres would be applied in succession taking out progressively more high frequency information For each filter length used the overlapping region of the grid is reduced so that its width does not exceed the length of the filter This minimises the region of the grids affected by the filtering Intrepid Gridmerge 3 5 release cl E il Grid Feathering Parameters M Memory Resident fast l Trim resampled grids Overlap Limit Filter lengt 2000 00 meters OK Cancel It is important to do a final feather using a 3x8 averaging kernel since near the edge of the overlap between grids there can be a significant change in Z value Depending on the number of feathering passes this sized kernel may not be reached so there 1s an option to ensure that a final 3x3 averaging kernel is invoked By default this option is switched on GridMerge checks that only one such pass is made in the event that this sized kernel would have been reached anyway The feathering operation always applies a final filter pass with a 1x1 kernel This is treated as a special case and is designed to feather the exact boundary of the grids being feathered The recommendation f
7. gt k Resample Grids Menge Grids k Trim Grids Preprocess Gridz Specifying Input and Output Directories The specification of inputs and outputs is mainly identical throughout GridMerge Typically the input is a sub directory and all grids within that sub directory are processed For the adjustment operations the output is also a sub directory and corresponding adjusted grid files of the same name are written into that output directory Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 8 Library Help Top Library Help Top q Back gt WARNING For all of GridMerge s adjustment operations the input grids and the adjusted output grids have the same file names If the same directory is nominated for both input and output then the input files will be overwritten by the output adjusted grid files It is recommended that the user specify a new output sub directory GridMerge will create the new directory and write the output grid files into it Recommended good practice is to keep the intermediate grid files from each stage of processing The user may choose to do some reprocessing with modified processing specifications using one of the saved intermediate adjusted grids as the appropriate starting point Specifying Input Directory Specify Input Image Directory Look in C raw_i
8. hundred or more input grids The input grids must comply with the following e All grids must be ERMapper format grids All grids must have a common datum projection and rotation e All grids must be linked by overlaps between individual grids 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 7 Library Help Top 4 Back gt Individual grids may have any cell size INTREPID s Projection Conversion tool can be used if necessary to bring grids to a common datum projection amp rotation GridMerge uses the areas of overlap between grids to determine the adjustments that need to be made so it is self evident that overlaps must connect all grids together in order for GridMerge to achieve the goal of computing corrections to bring all grids toa common level and surface GridMerge also has some utility operations Grid Operation PreProcess Grids which may be used to modify the grids in some way that might allow for improved application of GridMerge See GridMerge utility operations Boundary View of Grids One of the utility processes does not generate any modifications to grids but provides a handy visualisation tool which permits the user to visualise the extent of the overlaps between grids See Prepare Boundary View of Grids Intrepid Gidmerge 3 6 release cut 114 static File Beale Help Prepare Boundary Wiew of Grids Level Grids
9. the GridMerge tool band aware If so what does it output A The GridMerge tool IS band aware but currently it only outputs single band grids You nominate the band you want to merge The band number must be the same for all grids Q Is there a way to combine three merged radiometric grids into a single 3 band merged grid A This operation is available in the INTREPID Gridop module Q Gridmerge keeps telling me that I do not have sufficient overlap of grid points when in reality there are gt 500 The DC shift appears to run OK it is when I run the Surface Adjust when the issue starts A Your data has highlighted a weakness in the gridmerge reporting so this is something we need to address The main problem with the report is that when it reports the Total number of overlap points this is the count AFTER rejection criteria have been applied If you do a DC adjust and look at the report you will note that some grids have means around 2 or 3 million AND a range of 1 million or so Others have means of 5000 and AND a range of few thousand After the DC adjustment this means we have BIG differences The Surface adjust then counts the number of overlap cells and divided by a subsample parameter The user does not see this it also needs reporting The Surface adjust then rejects the cells with a difference larger than the Difference Limit This one is the killer It then fits a parabola surface to the difference grid and rejects any tha
10. 7_k p508_k p497_k p510_k p497_k p656_k p507_k p509_k p508_k p656_k p509_k p510_k p509_k p513_k Applying LSQ SVD analysis to determine final shifts for each grid Applying scale and shift adjustments to all grid data All grids transcribed to output directory C nt_data agso gmerge j1 Final overlap summaries Total number of overlaps 7 scale 1 Library Help Top 000 000 000 000 000 000 000 shift mean2 meanl 0 021 0 021 0 021 0 011 0 008 0 030 0 030 0 01 00 O1 00 01 00 00 2012 Intrepid Geophysics gridnamel gridname2 p497_k p508_k p497_k p510_k p497_k p656_k p507_k p509_k p508_k p656_k p509_k p510_k p509_k p513_k 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 21 Library Help Top Final grid adjustment summaries Shift Scale BeforeMean AfterMean diff Status 0 02 1 000 0 55 0 57 0 02 0 01 1 000 0 94 0 92 0 01 0 01 1 000 0 83 0 82 0 01 0 03 1 000 0 88 0 85 0 03 0 00 1 000 0 82 0 82 0 00 BASE 0 15 1 000 0 83 0 68 0 15 0 00 1 000 1 16 1 16 0 00 Elapsed time is 0 0 10 CPU time is 0 0 1 QONANO kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk End processing 10 3 2001 6 28 50 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Step 2 Surface Adjusted Grids kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Intrepid GridMerge v3 5 release c
11. 8 Total number of overlap points 2524 4 p509_k 3 1 p507_k 2815 p510_k 2924 p513_k 2564 Total number of overlap points 8303 5 p510_k 3 1 p497_k 2013 p507_k 48 p509_k 2924 Total number of overlap points 4985 6 p513_k 2 1 p507_k 20 p509_k 2564 Total number of overlap points 2584 7 p656_k 2 1 p497_k 2229 p508_k 1008 Total number of overlap points 3237 Total number of overlaps found 9 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 23 Library Help Top 4 Back gt Fitting degree 1 polynomials Iteration Max Adjustment Grid p497_k mean 0 193 X fit 0 667 Y fit 0 183 mean2 0 193 diff change 0 000 p507_k mean 0 194 X fit 14 753 Y fit 0 000 mean2 0 187 diff change 0 008 p508_k mean 0 186 X fit 1 259 Y fit 0 172 mean2 0 187 diff change 0 000 p509_k mean 0 135 X fit 2 315 Y fit 0 434 mean2 0 135 diff change 0 000 p510_k mean 0 115 X fit 0 221 Y fit 0 036 mean2 0 115 diff change 0 000 p513_k mean 0 120 X fit 15 032 Y fit 1 908 mean2 0 117 diff change 0 004 p656_k mean 0 223 X fit 3 273 Y fit 0 717 mean2 0 223 diff change 0 001 Applying 2D Polynomial Surface adjustments of degree 1 to output grids Grid Correction Summary List of corrections applied to each grid via Surface Adjustment and statistics on the final overlap differences Corrections listed below were added t
12. ID 1 RunType Standard Algorithm Statistics ScaleAndShift End Window Begin Box_LLEast 0 0 Box LLNorth 0 0 Box_UREast 0 0 Box_URNorth 0 0 Window End TrimGrids Begin TrimUnits Metres trimWidthMetres 1 0 TrimGrids End Parameters End Process End Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 40 Library Help Top lt 4 Back gt GridMerge tips and techniques Performance GridMerge can be very demanding of computer resources especially when operating on large numbers of grids In particular memory RAM and virtual memory swap file needs may be high For regular production 256Mb of memory and a large swap space say 1 Gb are recommended DC Corrections run relatively quickly Surface Adjust is a little slower Feather Merge is by far the slowest Any very large grid that is being re sampled or feathered will cause considerable delay The feather merge or feather operations can be made to run faster by increasing the output cell size but this is achieved at the expense of loosing data resolution The other penalty for doing this is a reduction of the number of cells in the overlap areas If overlaps are small then increased cell size would rapidly reduce the number of points within such overlaps to meaningless levels If the size of the output grid is large in comparison to the amount of RAM on the system then excessive
13. INTREPID User Manual GridMerge merging multiple grids T24 1 Library Help Top lt 4 Back gt GridMerge merging multiple grids T24 Top Introduction to GridMerge Overview The GridMerge tool is an innovative tool that allows the simultaneous merging of a large number of grids into a single merged grid file GridMerge is suitable for a wide range of gridded data types including potential field datasets magnetics gravity etc topography and bathymetry The scaling correction enables effective merging of radiometrics grids The typical GridMerge process is illustrated below Load directory otf gids Apply DC SAR or Optional are DC SAR amp Scam nid reference corrections Apply Surface Ads tment correction Optional are id reference Qptiona tanking of gid quality Sets processing order Xs Intrepid Map Composition v3 5 release cut 112 xz o 0 x File Edit Geographic Annotation View Bea SALLE Saha hae as SARK Soe eae K AUER Se SPER AA CREA ASNAN y An ps eT AN S A tk y Ro NSS Sero x se aT eo ee ANN Nis ERK TaN Sey Ne Ne pares Intrepid Mapcomposition Tool zoomout 2 The sun shaded image shown here is a GridMerge produced single grid of potassium channel radiometrics data from the Pilbara in Western Australia The grid was generated from seven original grids Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Gri
14. d LO gswa_merge a kit Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 4 Library Help Top 4 Back gt Execute GridMerge Si Intrepid Project Manager v3_5 release cut 101 OF x Fil Editors Levelling Display Printing Filtering FRadiometics Gravity Interpretation Utility Help ridding Current Director Stitch 2 Grids C a DFAN2001_0 Grid Operations Menge Multiple Grids Current Selection ee ee eee Drives Directories Datazets GRID _ers Empty Fe Bands GridMerge can be executed either from INTREPID s main menu or from the command line Either select Merge Multiple Grids from INTREPID s Grid menu e Or type gridmerge exe at the command line prompt Notes e Before starting GridMerge first browse to the directory above the input grid directory INTREPID s powerful batch processing options can be exploited by passing ina job file from the command line See GridMerge batch operation gridmerge batch MyJobFile job The GridMerge GUI will appear Intrepid Gidmerge 3 6 release cut 114 static File Grid Operation Help Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 5 Library Help Top 4 Back gt GridMerge Menu Choices a Quick Overview File Menu Choices
15. dMerge merging multiple grids T24 2 Library Help Top 4 Back gt Evaluation Licence Information Library Help Top GridMerge is a powerful software tool It is capable of combining together large numbers of gridded datasets to produce a single merged and seamless grid file which retains all of the detail of the input grids A free 30 day evaluation can be arranged by contacting Intrepid Geophysics at support intrepid geophysics com GridMerge was first released in 2000 Since that time the tool has been extensively tested within several client organisations often using large ensembles of grids including magnetics gravity and radiometrics It is the primary tool used to support the on going updates of the Australian Potential Field super grids These are produced at least yearly and reflect the ever improving nature of the understanding and observations of magnetics gravity and radiometrics A web enabled interface together with a multi threading cluster initiative is currently under way The intent is to drive down the time taken to achieve very high resolution super grids The 10 gigabyte magnetic map of Australia is taking about 100 hours in 2006 on a standard desktop PC using 700 base grids for a 100m resolution The aim is to achieve this in 3 hours by 2007 GridMerge performs complex data processing and many factors will contribute to the quality of output achieved In merging grids together the quality of the outpu
16. ds Having selected either of these operations the user must then specify both the input directory and type in a name for a new output directory to be created see Specifying Input and Output Directories One or more base grids can then be nominated A base grid is not adjusted Typically a good quality regional grid covering all or most of a project area and which is considered to have a correct reference surface would be specified as a base grid All other grids would then be adjusted to this reference surface Select Base Grids Select Base Grids Available Grids Selected Grids Cancel Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 11 Library Help Top lt 4 Back gt Ignore the requests for the High and Low Ranked grids These criteria are NOT USED in either the DC_Shift or the Scale_then_DC_Shift operations High Ranked Grids Create High Hank Grid List Unranked Fride Hinh Ranked Aride 1001 _a 1 E AE E E 1001_a_ gt Create Low Rank Grid List 1003 a Low Ranked Grids Ignore these rank is not l y used in the Scaling or Shift operations Intrepid Gridmerge v3 6 release cut Grd Shift Scale Parameters Overlap Limit is OK Help Cancel Specify the overlap limit This specifies a lower limit to the size of the overlap measured in pixels If an overlap has
17. dual parameters control the termination of the iterative surface adjustment process The process is stopped once the iteration limit is reached or the largest mean Z value of all difference surfaces falls below the maximum residual threshold Surface Degree sets the order of polynomial to be fitted The default is 1 first order polynomial which corresponds to fitting a slope A second order polynomial degree 2 might be useful in some cases if pairs of grids are proving difficult to match to each other The Difference Parameter parameter sets an absolute rejection limit which allows unreliable differences between overlapping grids to be rejected When overlaps are initially inspected any points where the absolute difference exceeds this limit are rejected Degree 1 Limit Degree N limit parameters are used to ensure that surfaces fitted to the differences between overlapping grids are meaningful when compared to the full extent of the grids involved Consider Grid A and Grid B below which overlap in two directions X and Y Ha X _ gt 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 35 Library Help Top 4 Back gt The percentage overlap refers to the linear ratio of the overlaps In the example above the overlap is about 90 in the Y direction and about 10 in the X direction If this percentage overlap is less than the
18. e merging multiple grids T24 18 Library Help Top 4 Back gt This dialog specifies what if any clipping should be applied to the final merged output grid file Intrepid Gridmerge v3 6 release cut 114 static Clip the merged grid No Clipping C Clip to predefined Polygon Clip to manually entered Rectange OK Help Cancel Choose Yes to initiate the Merge amp Feather operation For large numbers of large grids the processing time could be several hours When completed the finished message pops up and the report file presented Please Choose Do you want to proceed with the Merge and Feather No GridMerge report files Each of GridMerge s operations writes a report file rpt These reports summarise the operation performed the parameter settings and report a statistical summary Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 19 Library Help Top 4 Back gt Step 1 DC Shift Grids kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Intrepid GridMerge v3 5 release cut 101 Start processing 10 3 2001 6 28 40 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkxkxkk Process description DC shift grids by weighted least squares solution using SVD Program Control Input directory C nt_data agso gmerge part_pilbra Output directory C nt_data agso gmerge j1 Initial overlap s
19. e outer 2 rows or columns of a grid often contain some extrapolated data and can be an unreliable representation of the gridded parameter The Trim Grids operation can be used to trim these edges from the grids which may result in a better comparison of Z values between overlapping grids The process looks for Null defined boundaries in the grid and shrinks the boundary by a user defined distance defined in metres or pixels The trimmed grids are written to a new output directory as in the other operations Note that if grid overlaps are small this grid trimming may not be appropriate Intrepid Gridmerge 3 5 rel Trim Grids Parameters Trim Width Units Metres C Pixels DK Cancel Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 28 Library Help Top 4 Back gt Adjust Line Data NOT currently implemented in GUI Library Help Top In the pragmatic world of processing field data individual surveys recorded in different eras can develop systematic differences e g the removal of IGRF has evolved from what was at best an approximation through to a more valid correction in modern processing GridMerge provides a solution for adjusting such systematic grid differences The Adjust Line Data operation allows the adjustments made to the grids to be captured back into each original line data base It can be conside
20. een it and its neighbours The surface takes the form of a pair of polynomials of the defined degree one fitted to the differences as a function of row number the other as a function of column number The difference surface with the largest mean Z value is then subtracted from its corresponding grid The process iterates until the largest mean Z value of all difference surfaces falls below a given threshold or a maximum number of iterations 1s exceeded Note 1 dimensional polynomials of degree N are applied in the row and column direction Because the iteration is done in a piecewise manner the lack of an XY cross term generally does not matter For best results Surface Adjust should be run on grids that have already been DC_Shifted or Scaled and DC_Shifted If not large tilts could be applied to the grids 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 13 Library Help Top 4 Back gt ei Intrepid Gidmerge v3 6 release cut 114 static arid Operation Help Preprocess Grids gt P Level Grids DC shift grids Menge Grids F Scale THEN OC shift grids Surface Adjust grids Specify the input directory Normally a DC_Shift has been done previously and those saved outputs would be specified as the input to Surface Adjust Specifying Input and Output Directories Again the output directory is normally a new directory Type in a name for a new ou
21. ements Substitute your list of grid for Fred a b c etc 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top GridMerge merging multiple grids T24 41 q Back gt If necessary change the Format in the export statement to Format MapInfo MapInfo Begin GroupBy Yes MapInfo Begin GridMerge Pro GridMerge Pro offers options that are not available through standard GridMerge The most important of these is the capability of writing the results of the grid merging back into one or more database fields Effectively this is the same as applying microlevelling on multiple line datasets simultaneously To activate GridMerge Pro you need to do the following e You must have a valid license to run Gridmerge Pro In the install_path config install cfg file you need to set the system parameter INTREPID _MENUS 1 This will turn on all of the special options Displaying differences across columns and rows Library Help Top The GridMerge Surface Adjust function applies 1dimensional polynomials in the row and column directions These can be examined in GridMerge Pro by checking the Plot difference surface fits button in the Surface Adjust Parameters box After pressing Apply a graph will appear showing the differences across columns and the differences across rows in profile form This allows you to go forward one grid at a time through the row and column profile polynomials
22. er Manual GridMerge merging multiple grids T24 16 Library Help Top 4 Back gt This grid must be placed in the directory ABOVE the input adjusted grid directory Specify Output Image ki ES Look in 4 grids a GF e El boundary view dc shifted raw input suit adjusted a boundary composite PD ers File name menged mag Files of type Data GRID ers Cancel T Open as read only Ignore the Select Base Grids this is not used by Feather Merge Select Base Grids Select Base Grids Available Grids Selected Grids 1001 a_1 1001 a 5 1003 a gt 1003_a NE 2 1003 a NE_3 Ignore this base grids is not used in the Feather Merge operation In merging grids the highest quality most detailed grid should be on top in the final merged output On the other hand a regional grid with large cell size and generally lower information content should be a lowly ranked grid which is only used if no other more detailed grid is available The Merge process uses a default ranking the smallest input grid cell size is highest ranked For a given cell size the input grid with most data points ranks highest Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 17 Library Help Top Library Help Top lt 4 Back gt The user can specify a preferred ranking of
23. es are replaced by this number thus a grid of 1s a grid of 2s etc 2 Runasimple merge operation to composite these special grids into one merged special grid file 3 Load the merged grid into ERMapper to visualise the spatial relationships between the grids This simple visualisation can be used to rapidly identify any grids with little or no overlap with adjacent grids Note that the number assigned to each grid is the sequential order in which it was processed These sequence numbers and the associated grid file names are tabulated in the processing report file so a grid name can be determined by querying the Z value of a grid in ERMapper and cross referencing to the list of grid names Intrepid Geophysics has a batch file that can be run to generate an Arc Shape or MapInfo file which includes all grid boundaries together with attribute data such as erid file name etc Then use ArcView or MapInfo to view the grid relationships and assess extents of overlaps Contact Intrepid Geophysics at support dfa com au for a copy of this file 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 26 Library Help Top q Back gt Resample Grids Library Help Top 2 Intrepid Gidmerge v3 6 release cut 114 static File EGR Help Prepare Boundary YWiew of Grids Level Grids gt a Resample Grids Merge Grids k Trim Grids Prepr s Grid
24. g the Advanced Menus system parameter INTREPID MENUS 4 The standard GUI is displayed below Intrepid Gridmerge v3 6 release cut 114 sta__ Surface Adjustment Parameters Hin overlap Limit Max overlap Limit Maximum Iterations 100 Maximum R esidual Surface Degree Degree 1 Limit 20 00 Degree H Limit 40 00 39 00 Ti Differences Limit OK Help Cancel Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 34 Library Help Top Library Help Top lt 4 Back gt Allow DC shifts if degree gt 0 is normally unchecked which constrains the mean value of a surface fitted to grid differences to be zero Thus a grid would be warped but not DC shifted If Surface Adjustment is creating DC errors the problem may only become apparent during subsequent feather merging Try re doing the Surface Adjustment with Allow DC shifts if degree gt 0 checked Min overlap Limit Max overlap Limit parameters control the number of overlap points used when fitting difference surfaces Overlaps with less points than the lower limit are ignored This lower limit should be set at a level above which the results could be regarded as being statistically meaningful Overlaps with more points than the upper limit are sub sampled so that the number of points actually used falls just below this limit Maximum Iterations Maximum Resi
25. gh Each grid is overlayed by those that follow it in this list 1 p508_k p507_k p513_k p510_k p509_k p497_k p656_k Elapsed time is 0 5 20 CPU time is 0 0 1 ONANO kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk End processing 10 3 2001 6 38 52 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk GridMerge utility operations GridMerge has some additional utility processes to assist in planning a GridMerge Job or to do some pre conditioning operations to the input grids prior to GridMerging them i Intrepid Gridmerge 3 6 release cut 114 static File MeEimiin Ea Help Prepare Boundary Wiew of Grids Prepr arids gt F Level Grids gt k Resample Grids Menge Grids gt e Trim Grids Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 25 Library Help Top lt 4 Back gt Prepare Boundary View of Grids Library Help Top This utility process generates a special copy of the grid files which allow the user to visualise the extent of the overlaps between grids A series of simple steps are needed to generate the visual picture of grid extents and overlaps 1 Execute Prepare Boundary View of Grids As with several other operations the output grids should be written to a new sub directory The output grids created by this process are assigned a unique integer number each grid s Z valu
26. grids by nominating both high ranked grids and also low ranked grids Any grids not specified will be ranked according to the default criteria High Ranked Grids The lowest ranked grid is used only when no Create High Rank Grid List other grid is available Unranked Grids at 7 Enter a name l m i HE J for the final _a_NE_ 1003 a NE 3 merged output Create Low Hank Grid List The highest ranked grid will be on top in Unranked Grids the final merged grid 1001_a_1 oe Low Ranked Grid 10035 a NE_3 The following dialog is used to set some of the feathering parameters See Grid Feathering for more details Note that further control of the feathering process 1s available through INTREPID s batch processing job files see GridMerge batch operation Briefly Intrepid Gridmerge v3 6 release cut 114 s__ Grid Feathering Parameters Memory Resident fast l Trim resampled grids Filter lengt 2000 00 meters OF Cancel e Check Memory Resident for fast execution of smaller jobs Trim allows GridMerge to trim the very edges of grids where some extrapolation during gridding may result in less accurate grid values e Overlap limit specifies a minimum number of points in an overlap between two grids e Filter length can be increased to increase the amount of smoothing 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerg
27. hift and scales determined directly from grids using standard deviations amp means of overlaps and output grids adjusted Base grid weighting factor 200 00 Overlap regions restrictions Minimum overlap size 500 pixels Processing Summary Grid sequence for processing 1 p497_k p507_k p508_k p509_k p510_k p513_k p656_k Overlap statistics Total number of overlaps in island 1 is 7 Gridl Grid2 no points Mean Stnd Dev ovlp Mean Stnd Dev ovlp gridnamel gridname2 1536 0 60 0 40 0 6 0 64 0 49 3 1 p497_k 1 p508_k 1 2020 1 11 0 50 0 7 1 13 0 52 1 1 p497_k 1 p510_k 1 2259 1 42 0 69 0 8 1 43 0 83 3 5 p497_k 1 p656_k 1 5713 0 85 0 52 11 3 0 87 0 47 2 2 p507_k 1 p509_k 1 1018 1 07 0 46 Aad 1 08 0 56 1 6 p508_k 1 p656_k 1 5943 0 62 0 29 2 3 0 59 0 31 3 1 p509_k 1 p510_k 1 2600 0 96 0 40 1 0 1 08 0 46 4 0 p509_k 1 p513_k 1 No base grid defined via program control Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Library Help Top Selection algorithm has therefore chosen p510_k GridMerge merging multiple grids T24 20 4 Back gt Initial overlap summaries to be used to calculate the final grid shifts by LSQ SVD analysis Total number of overalps 7 scale 1 000 000 000 000 000 000 000 shift mean2 meanl 0 041 0 021 0 011 0 019 0 005 0 030 0 118 0 04 02 01 02 01 03 12 gridnamel gridname2 p49
28. l processing management Enter an appropriate name for a new directory to be created The output gds will be written to this directory formation about _ The process you have selected equires a new directory into which to deposit the adjusted grids Inthe following chooser type in a name of a directory that does not already exist Specify Output mage Directory ki Ed Look in E grids ce l raw input File name dc_shifted ji Files of type Data Cancel T Open as read only In this example the input directory raw_input and the new output directory dc_shifted are both sub directories of the grids directory Step 1 DC_ Shift or Scale then DC_ Shift The first GridMerge operation to be applied is usually a Shift or Scale and Shift operation designed to bring all datasets to a common scale and level The choice of DC Shift or Scale then DC Shift will depend upon the input datasets Usually Potential field data magnetics gravity use DC_Shift Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 10 Library Help Top 4 Back gt If the DC_Shift operation is selected the Scale Factor is set to 1 a Intrepid Gidmerge 3 6 release cut 114 static arid Operation Help Preprocess Grids gt Level Grids gt DC shift grids Menge Grids gt F Scale THEN DC shift grids Surface Adjust gri
29. le IMPORTANT A typical GridMerge processing task requires several sequential GridMerge operations where each operation performs a specific phase of the overall job and frequently the output from one operation becomes the input to the next operation Since GridMerge is often applied to processing large numbers of grid files many GridMerge operations expect data to be organised in directories and outputs will be written to separate new directories The input and output adjusted grid files have the same file names and thus the outputs must be written to a new directory in order not to overwrite the input files A systematic approach to using directories is essential A typical directory structure after using GridMerge is illustrated below Note that the raw input grids and the various intermediate stages of adjustment are all contained within separate directories Additionally there is the final merged grid file See Specifying Input and Output Directories for further details of directory specification Mul t t 3 as a E DC ted Grids Sub directory Grids Sub directory me Surface Adjusted and kolc ms dos_ 6 DC Corrected Lo Ram input DC Corrected kald gserv2k_d B SA_corected kale gservzk_e i merged_output_agrid LI Cdrom Grids Sub directory E jhwork Original data Final merged grid O nt data O agso ese O agso raw O dnre_marine 9 Ebagoola GidMende JS DC corecte O Ran input JO S4_ correcte
30. less than this limit of pixels then no statistics are computed for that overlap Choose this limit such that statistically meaningful data can be derived from the overlap region Please Choose Do you want to proceed with the DC Shift Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 12 Library Help Top lt 4 Back gt Choose Yes to initiate the Scale then DC_Shift computations For large numbers of large grids the processing time could be several hours When completed this message pops up Information Gridhlerge processing completed gndkierge rpt Notepad OF x File Edit Search Help K EHEREBREEHHREHEHEHREHEEHHEEHHREHREHREEHRHHREBRHRHEBRHEHHHHRHEHREHEHREHRENHEREE Intrepid Gridmerge v3 6 release cut 114 static Start processing 3 6 2001 20 34 55 HEEHEEEEEEHEEREHEEEEREEEEEHEEHEREHREHREHREHRHEEEEEEHREEEEREREHEEREEEE Process description DC shift grids by weighted least squares solution using SUD Program Control Report file gridHerge Input directory C a_DFA 2661_66_Gridte directory C a D A brief processing report is written to the report file default report file is GridMerge rpt Step 2 Surface Adjust Grids Library Help Top This operation inspects all the input grids and computes a two dimensional surface for each grid which represents the differences in Z values betw
31. nput 10013 1 GRID a 1003_a 7 GRID a 1003_a NE_3 GRID ka 1001_a 1 PD 1003_a_7 PD a 1003_s NE_3 PD 1001_a_1 PD ers 1003_a_7 PD ers 1003_a NE_3 PD ers a 1001_a_5 GRID 1003_a NE_2 GRID a 1001_a 5 PD 1003_a NE_2 PD 1001_a_5 PD ers 1003_a NE_2 PD ers Filename 1001_a_1 GRID Files of type Data Cancel T Open as read only Browse to the directory containing the input grids to be processed For UNIX simply select the required input directory For Windows the file chooser requires a filename rather than a directory name Browse into the input directory and choose any file Specifying Output Directory Immediately after specifying the input directory GridMerge pops up a message below advising that an output directory is required This output directory should be a new directory and must be at the same level as the input directory never a sub directory of it The adjusted output grid files are written into this output directory 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 9 Library Help Top lt 4 Back gt Choose an output sub directory name appropriate to the selected GridMerge operation Frequently the output from a given process becomes the input toa subsequent operation Sensible naming of the directories each containing outputs from a specific operation is essential for carefu
32. o the original grids Ref CORRECTIONS FINAL OVERLAP DIFFERENCES Seq Count Mean Minimum Maximum Mean sd Minimum Maximum Grid 1 0 0 000 0 000 0 000 0 002 0 252 0 964 1 032 p497_k 2 0 0 000 0 000 0 000 0 001 0 251 0 840 0 920 p507_k 3 0 0 000 0 000 0 000 0 001 0 242 0 749 0 807 p508_k 4 0 0 000 0 000 0 000 0 001 0 185 0 920 0 840 p509_k 5 0 0 000 0 000 0 000 0 001 0 153 0 543 0 555 p510_k 6 0 0 000 0 000 0 000 0 001 0 158 0 589 0 577 p513_k 7 0 0 000 0 000 0 000 0 004 0 282 1 032 0 964 p656_k Elapsed time is 0 0 10 CPU time is 0 0 1 QONANO kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk End processing 10 3 2001 6 31 48 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 24 Library Help Top 4 Back gt Step 3 Feather Merge Grids kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Intrepid GridMerge v3 5 release cut 101 Start processing 10 3 2001 6 33 32 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Process description Seamless feather and merge grids into a single grid Program Control Input directory C nt_data agso gmerge j2 Output grid C nt_data agso gmerge f1 Output grid parameters are X origin 115 680000 Y origin gt 20 485000 X cell size 0 001000 Y cell size 0 001000 Processing Summary Grid ranking for feathering low to hi
33. onstrains the number overlap points used in fitting the difference surface between two grids e Max Iterations amp Residual control the termination of the iterative surface adjustment process e Order of polynomial used in fitting the surface Default 1 ie slope adjustment but a second order polynomial 2 can be useful e Degree Limits ensure that surfaces fitted to the differences in the overlap are meaningful when compared to the full extent of the grids involved Differences Limit sets a rejection limit Differences observed in the overlap between two grids are rejected if the absolute value exceeds this limit Please Choose Do you want to proceed with the Surface Adjust No Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 15 Library Help Top 4 Back gt Choose Yes to initiate the Surface Adjust operation For large numbers of large grids the processing time could be several hours When completed the finished message pops up and the report file presented E gridMerge rpt Notepad Information Ea File Edt Search Help bh A Gridkenge processing HH HEH HHH HHH HHH HEHEHE HEH HHH HEHEHE HHH HE HHH HH HEH HHH HEHEHE HEHEHE HEHEHE HEHEHE IEE completed Intrepid Gridmerge v3 6 release cut 114 static Start processing 4 6 2661 2 7 42 HHH HHH HH HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH KKK E E E
34. or feathering is to specify enough passes such that with the filter length being halved for each pass a final 3x3 kernel is reached If the Number of Passes is set too large the filtering iterations will stop once a 8x3 kernel is done and the final 1x1 type kernel is applied To increase smoothing increase the number of passes and perhaps the filter length The default settings are good starting points If there are edge problems in the final merged grid ascertain the edge dimension using the query option in INTREPID s Visualisation tool and set an appropriate filter length 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 33 Library Help Top lt 4 Back gt Grid Shift Scale Intrepid Gridmerge 3 5 release Grid Shift Scale Parameters Overlap Limit OF Cancel Any overlaps between grids with less points than this limit are discarded Small overlaps do not provide a sufficiently large population to derive meaningful statistics Surface Adjustment It is strongly recommended that this Surface Adjustment operation be applied only to grids that have already had DC Shift or Scale Then DC Shift adjustments done to them Surface Adjustment fits a surface to the Z differences between overlapping grids This dialog set parameters that control that fitting process Some items in this GUI are only available via INTREPID job files or by settin
35. owing operations Operation Operation Operation Operation Operation Operation Operation Operation Operation Operation Operation Operation Base Grids H He Ht HHH HH H H OH OH H OH OH H Resample Shift ScaleThenShift ScaleAndShift SurfaceAdjust Merge Feather Feather amp Merge Condition BoundaryView AdjustToReference AdjustLineData ab c High RankedGrids a b c Low RankedGrids a b c Interpolation Newton_4th_Order Reference Begin UseReference No Cellsize 999 9 x origin 999 9 y_origin 999 9 Reference End Iterate Begin MaxResidual 0 05 Iterations 100 Iterate End Library Help Top 2012 Intrepid Geophysics q Back gt INTREPID User Manual GridMerge merging multiple grids T24 39 Library Help Top 4 Back gt SurfaceAdjustment Begin RejectOutliers No AllowDCshift No DegreeZeroFirst No UseRowColAverages No WeightPointLimit 10 ListCoefficients No PlotSurfaceFits No Degree 2 DegreelLimit 20 0 DegreeNLimit 90 0 DifferenceLimit 99 0 SurfaceAdjustment End OverlapConstraints Begin MinOverlapLimit 500 MaxOverlapLimit 5000 OverlapConstraints End Feathering Begin featherInMemory Yes Final3x3Pass Yes TrimResampledGrids No filterLength 5000 0 filterPasses 6 Feathering End AdjustLineData Begin CalculateScaleFactor No SurfaceDegree 2 AdjustLineData End ScaleAndShift Begin BaseGridWeight 200 0 ScaleAndShiftDBgroup
36. perimentation we have found that it 1s often better to correct a subset of the grids and merge them into a single grid This merged grid is then adjusted with the remaining grids For example consider the case of an area covered by about 16 1 250 000 map sheets Most of the surveys corresponded well with 1 250 000 sheet areas but three of the areas were a real montage of small postage stamp sized surveys A much better result was obtained by adjusting these three 250 000 areas individually producing a feather merged grid for each The rest of the grids and the merged ones were then processed normally 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 29 Library Help Top Library Help Top lt 4 Back gt To allow for such cases when the line data adjusting tool looks for a match for a grid name in the database directory it also looks for a directory with the same name as the erid If one is found it expects to find a whole lot of datasets in this directory and applies the corrections to every one To use line data adjustments in such cases the corrections must be applied in two stages 1 After a merged grid is produced the corrections generated by its uncorrected corrected grids are applied back to the corresponding data bases 2 These datasets are then placed in a sub directory with the same name as the merged grid in the database directory and Adjust line da
37. red to be a micro level operation Intrepid Gridmerge 3 5 release cut 1 ii Adjust Line Data Parameters Calculate scale factor Surface Degree OF Cancel The adjustment process is done by comparing the original grids with the final corrected ones recalculating the various parameters from their differences and then applying them as a function of X Y back to the nominated Z field The only parameters the user has to specify is the maximum degree of the surface fit made to the grids and if GridMerge applied a scaling factor to the grids The process takes a lot longer if the scaling parameter needs to be calculated as an iterative procedure is involved GridMerge has to calculate the scaling factor as the ratio of the standard deviations of the two grids then work out the surface fit The surface fit is removed from the final grid allowing a new estimate of the scaling factor The process iterates until the changes to the Scaling factor are insignificant giving the required scaling factor and surface fit The line datasets and the corresponding grid files are stored in separate directories There is an input directory for uncorrected grids one for corrected grids and another for line datasets For each grid file in the uncorrected grid directory a corresponding corrected grid and also a line dataset with the same name are expected to be found in their respective directories There is one exception By ex
38. s gt Whenever the GridMerge tool needs to compare grid Z values and the pixels are not coincident grid re sampling is done on the fly Alternatively the Resample Grids operation can be used This utility interpolates the grids and re samples so that all pixels fall on a common mesh The X Y origin of this mesh and the mesh pixel size can be defined via the Grid Reference Parameters dialog See Grid Reference If not specified the default origin used is the North West extreme of all the input grids and the pixel size the smallest from the input grids Various smoothing and clipping options can also be specified via relevant dialog boxes GridMerge operations will take less time on re sampled grids since they obviate the necessity for subsequent re sampling If the grids have a large range of cell sizes however the re sampled grids may require substantially more disk space Note If a re sampling of more than 5 to 1 in cell size is attempted the re sampling algorithm breaks this into several intermediate steps to ensure sagging is not introduced into the re sampled grids 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 27 Library Help Top 4 Back gt Trim Grids Intrepid Gidmerge 3 6 release cut 114 static File MEE Help Prepr pero Frepare Boundary Wiew of Grids Level Grids gt k Resample Grids Menge lrids gt d Th
39. s are used to provide user input for several different operations In addition to parameters which can be specified within these GUI dialogs there are also further parameters which modify how GridMerge operates which are available only via INTREPID s batch mode processing Those parameters are described elsewhere Grid Smoothing Interpolation Library Help Top Intrepid Gridmerge 3 5 release c it Grid Smoothing Parameters Smothing Iterations 100 Haximum R esidu al 0 05000 OF Cancel These parameters are used whenever grids are re sampled They apply to the interpolation of a re sampled grid to ensure it corresponds closely with the grid it is derived from The parameters are analogous to those used when gridding line data It is recommended to leave at the defaults Reduce the number of iterations and increase the Maximum Residual if testing large grids 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 31 Library Help Top q Back gt Grid Reference When performing merging feather merging or re sampling operations it 1s usually necessary for input grids to be interpolated so that all pixels fall on a common mesh The X Y origin of this mesh and the mesh pixel size can be defined via the Grid Reference parameter dialog If not specified the origin used is the North West extreme of all the input grids and the pixel size the smalles
40. shes to access all the inner methods and settings of the tool via the a more compehensive GUI Some access to the more comprehensive menu options can be had by editing the install cfg file in the Intrepid config directory The option to enable is the GRIDMERGE_MENU Also supported in GridmergePro is the extra step of taking the final levelled signal back to the original observed channels in line datsets This can be thought of as a Super micro levelling option 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 3 Library Help Top lt 4 Back gt How GridMerge Works GridMerge works by applying a range of level and surface corrections to multiple grids that are linked by overlaps An overlap is where two grids share a spatial region GridMerge statistically analyses the data within the overlap for each pair of grids and uses these results to compute the appropriate level and surface adjustments for each grid Once the grids have been adjusted to a common level and surface a feathering and merging operation amalgamates the grids into one seamless grid GridMerge can be thought of as a two stage process 1 Compute Corrections to generate Adjusted Grids one or more separate correction processes e each of these write out a sub directory of adjusted grids 2 Final Merge e uses the adjusted grid files from the appropriate sub directory e writes out a final merged grid fi
41. t are more than 8 stddevs away So you can get around this by increasing the Difference Limit to say 10000 Library Help Top 2012 Intrepid Geophysics 4 Back gt
42. t from the input grids Grid Reference Parameters Check this box AND Enter one or more values here or leave some at default 999 9 gt gt To use any parameters from the Grid Reference dialog The Use reference box must be checked One or more of the default entries 999 9 must be changed to actual user specified values positive values Note It is allowable to specify just the cell size say and leave the origins as defaults This might be used to force GridMerge to use a cell size that is not the smallest cell size of all the grids for example Level to Reference not implemented in GUI Grid Feathering Several of GridMerge s feathering options are only available through INTREPID job files These include the Number of Passes and Final 3x3 pass parameters mentioned below Some limited parameters can be set in the Feathering Parameters dialog shown below Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 32 Library Help Top Library Help Top 4 Back gt The feathering process attempts to seamlessly join overlapping grids It essentially smooths the differences between the Z values of the overlapping grids and then adjusts the grids by these smoothed differences The smoothing takes the form of a square averaging kernel the size of which is the user defined filter length Several such
43. t grid is naturally dependent on input grid qualities Typically gridded datasets to be merged will have variable quality and resolution For optimal results it is essential that the user be familiar with all of the quality issues in the grids being merged so that appropriate user choices are made which will enable GridMerge to exploit the better quality of some grids compared to the lesser quality or resolution of other grids This guide has been designed to assist users to get started with GridMerge and to learn how to use their understanding of input grid data quality to make processing choices which achieve the best output results Some experimentation may be needed in order to develop an understanding of the effects of various user choices and to build up experience in using GridMerge to best effect All of the main functionality of GridMerge is implemented in the simplified graphical user interface GUI and those features are described in this manual GridMerge like other parts of the INTREPID data processing package can also be run in batch mode from a command prompt using parameters specified in a job file The SHOW button lets you see the current state of the job Some of GridMerge s capabilities are currently not implemented in the GUI but are only available in the batch processing environment Some aspects of the batch processing are briefly covered in this manual GridmergePro is available for the more serious user who wi
44. ta applied again in the normally way with all the remaining grids To use this some planning must be made before merging Set up the system before starting to merge the grids and it 1s relatively simply to ensure the required directory structure and naming convention is adhered to All files are defined via the File gt Specify Adjust Line Data menu Once a Z field has been defined the GUI uses the directory containing the dataset as the directory in which all the datasets are to be found It uses X and Y fields aliases if they are defined You can override this later via the GUD Note THE TOOL EXPECTS each dataset to have the same X Y and Z fields With lots of datasets this is a better system than inspecting each dataset s aliases and using X Y Z fields defined there It has been found that adjusted line data is very useful and grids created by re eridding the updated datasets are identical to the corrected grids produced by GridMerge Down to the rounding error for reals 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 30 Library Help Top lt 4 Back gt GridMerge parameters Many of GridMerge s parameters are specified via GUI dialogs All parameter dialogs are described in detail in this section Note that some of these dialogs have been described briefly in preceding descriptions of GridMerge s main operations Furthermore many of these dialog
45. to review them Polynomial Surface Fit To Overlap Differences Differences across Columns ewoa_ east magfinalmi e 6 46 1 00 165 50 330 00 Differences across Rows amp G4 cues gt cpr magi nahn J ma Ee ce a oD ee ee 6 46 5 1 00 213 00 425 00 NEXT AUTOMATIC CANCEL 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 42 Library Help Top 4 Back gt Frequently asked questions Q I am trying to merge a lot of grids and the output grid is not satisfactory How can I determine what is wrong A Usually a problem with the output feathered and merged grid is caused by particular problems with one or more source grids Inspection of the statistics in the DC shift report file will help you to identify which source grids may have problems Q What are some of the benefits of the GridMerge tool compared to the older GridStitch tool A GridMerge sees ALL overlaps whereas GridStitch only sees overlaps with the base grid A GridMerge can be tuned to ignore small areas of overlap A The GridMerge set of results will have more feathered edges than GridStitch GridStitch will only be feathered along edges with the base grid GridMerge will be feathered along all overlaps A GridMerge uses all overlap pixels whereas GridStitch only uses edge pixels A GridMerge can trim edges A GridMerge can work within a polygon Q Is
46. tput directory to be created Specifying Input and Output Directories Again specify one or more base grids Select Base Grids Select Base Grids Available Grids Selected Grids 1001 a_1 1003 a 1001 a 5 gt gt 1003 a NE gt 1003 a NE_3 All gt gt but the ranking selections can be ignored these are not used by Surface Adjust Low Ranked Grids Create Low Rank Grid List Unranked Grids Low Ranked Grids 1001 _a_1 a 1001_a_5 i 1003_a_7 High Ranked Grids 1003 a NE Create High Rank Grid List T a ME 7 ee a ee Unranked Grids High Ranked Grids 1001_a 1 1001 a5 Ignore these Rank is not 1003 a used in the Surface Adjust 1103_a_NE_ operations a NF Library Help Top 2012 Intrepid Geophysics q Back gt INTREPID User Manual GridMerge merging multiple grids T24 14 Library Help Top 4 Back gt Surface Adjustment requires user input for a series of parameters which control the operation These parameters are described in detail in Surface Adjustment Intrepid Gridmerge v3 6 release cut 114 sta__ Surface Adjustment Parameters Hin overlap Limit Hax overlap Limit Maximum teratio ngioo Maximum A esidual Surface Degree Degree 1 Limit Degree N Limit 4 40 00 44 00 Differences Limit OF Help Cancel Allow DC if unchecked constrains the mean value of a surface fitted to grid differences to zero e Overlap limits c
47. use of the virtual memory system may result In these cases disabling the memory resident option in the Feathering parameters dialog will use less RAM by writing to disk This option is likely to be faster when heavy swap conditions would otherwise occur Log Files and Troubleshooting All GridMerge operations write a processing summary to a report file By default this is called gridmerge rpt and is located in the start directory This file should list problem grids as well as report on adjustments made INTREPID modules also write progress comments to console UNIX or toa secondary file called nt log Windows The progress of a large job can be monitored by viewing these log file outputs In UNIX view the console window On a Windows computer with the UNIX utility tail available open a command window and execute tail f nt log This will simulate a UNIX console window effectively reporting to the command window Polygon Generation Library Help Top Intrepid Geophysics has a batch file that will produce a single polygon in Arc MapInfo or INTREPID format along with associated meta data grid name cell size Projections Datum extents statistics etc This is extremely useful for working out which grids are which An example of this job file is on ftp dfa com au pub people gridmerge The file is called outline_generate job To use it you need to Change the directory and file locations to reflect your arrang
48. ut 101 Start processing 10 3 2001 6 31 38 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Process description Grid Name p497_k p507_k p508_k p509_k p510_k p513_k p656_k Level grids by fitting polynomial surfaces to overlap differences Program Control Input directory C nt_data agso gmerge j1 Output directory C nt_data agso gmerge j2 Overlap regions restrictions Minimum overlap size 500 pixels Maximum overlap size 5000 pixels Surface fitting parameters Polynomial degree of surface J Degree 1 Limit 20 0 Degree N Limit 90 0 Differences Limit 99 0 Reject outliers in polynomial fits NO Allow net DC shift of surface NO Apply degree zero surface fit first NO Use row and column averages in fit NO List fitted surface coefficients NO Maximum number of iterations 100 Maximum residual 0 050 Point limit for weight of 1 0 10 Library Help Top 2012 Intrepid Geophysics lt 4 Back gt 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 22 Library Help Top 4 Back gt Processing Summary 1 p497_k p507_k p508_k p509_k p510_k p513_k p656_k List of overlaps for each grid Seq Grid No Overlaps Grid Overlap Pair Number Overlap Points 1 p497_k 3 1 p508_k 1516 p510_k 2013 p656_k 2229 Total number of overlap points 5758 2 p507_k 3 1 p509_k 2815 p510_k 48 p513_k 20 Total number of overlap points 2883 3 p508_k 2 1 p497_k 1516 p656_k 100
49. v3 6 release cut 114 static File Meini Help Preprocess Grids gt Level Grids gt DC shift grids Merge Grids t Scale THEN OC shift grids Tn Suface Adjust grids Level Grids has three sub menu choices which provide GridMerge s three level and surface adjustment processes These are core processes within GridMerge and are covered in detail in Basic GridMerge Each of these processes reads a sub directory of input grids computes adjustments and writes out corresponding output grids into a specified output sub directory Intrepid Gidmerge 3 6 release cut 114 static File BERGE Help Preprocess Grids gt Level Grids Menge Grids Merge lrids by Pasting Te tiege and Feather Grids Merge Grids has two menu choices for doing the final GridMerge operation viz reading input from a sub directory of levelled amp surface adjusted grids and combining these into one final seamlessly merged output grid file This is the second of GridMerge s two main processes and is discussed in detail in Basic GridMerge Basic GridMerge Preparation Library Help Top GridMerge requires all of the grids that are to be merged be collected together into a single directory Conversely all grids within that sub directory are regarded as input and will be processed by the chosen GridMerge operation There is no limit to the number of grids in this directory GridMerge is routinely run with one
50. ys will be the lowest ranked survey and would only be used where no other grid data was available It is not necessary to rank all surveys those that are not ranked would have an intermediate ranking between the high and the low and would be ordered internally according to GridMerge s default ranking criteria High Ranked Grids Create High Rank Grid List Unranked Grids 1001_a 1 1001_a 5 1003_a_N 1003_a_N m m wd MA Low Ranked Grids Create Low Rank Grid List Unranked Grids Low Hanked Grids 1001 a 1 1003 a NE_3 1001 a 5 f 1003_a_NE_2 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual GridMerge merging multiple grids T24 37 Library Help Top 4 Back gt Window not implemented in GUI Allows bounding polygons and rectangle to be specified Clips the output merged grid or adjusted grids S Intrepid Gridmerge 3 5 release cut 7 Ioj x Fil Operation Parameters Window Help Load Polygon Specify Rectangle Interpolator not implemented in GUI It is recommended that all interpolation is performed using Newton 4th Order local operator which is the default GridMerge batch operation The following is an example of an INTREPID batch job file A properly constructed batch file can be created by setting up a processing task in the GridMerge GUI then choosing File gt Save Options from the menus and saving the file as a
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