Old spectral domain grid filters (OldGridFFT)
Contents
1. Directional cosine filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Filter direction Degree of cosine function Pass Reject Pass Pass the data near the filter direction within the cosine function rolloff range Complex filters OldGridFFT The Complex filters are commonly used special combinations of filters gt gt To specify a Complex filter 1 Ifyou are using the Pseudo Gravity or Susceptibility filters ensure that you have specified the Earth s core magnetic field data See Specifying the Earth s core magnetic field direction and intensity OldGridFFT above 2 Choose the option you require from the Complex menu File Gradients Reductions Continuations Complex Standard Directional Pseudo gravity Susceptibility Decorrugation Apparent density INTREPID displays a dialog box for entering parameters 3 Edit the parameters as required and choose OK Pseudo Gravity transformation OldGridFFT gt gt To specify a Pseudo Gravity filter 1 Make sure you have specified the core magnetic field direction and intensity for the survey See Specifying the Earth s core magnetic field direction and intensity OldGridF FT above for instructions INTREPID will automatically use these values for the filter Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain2. Parameters Thickness of the Earth Model Apply OldGridFFT When you choose Apply INTREPID will perform the processing that you have specified Before you choose Apply you must have specified the input and output dataset names the type of processing you require and parameters that you wish INTREPID to use When INTREPID has completed the process it displays the Filtering process successfully completed message box Intrepid Grid Filter tool V3 1 Beta Message Filtering process successfully completed Choose OK to dismiss the box Stop OldGridFFT gt gt To abandon processing after it has started Choose Stop from the Spectral Domain Grid Filters Main window Exit OldGridFFT gt gt To exit from the Spectral Domain Grid Filters tool Choose Quit from the File menu INTREPID will exit from the Spectral Domain Grid Filters tool Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 30 Library Help Top lt 4 Back gt Other uses of the pre filter and post filter transformations OldGridFFT You can perform any of the following pre filter and post filter transformation tasks separately on a dataset Removing and restoring trends 1n datasets Expanding and restoring the dimensions of data grids Filling data gaps in grids by interpolation Finding and removing interpolated values in grids gt gt To use the
3. 1 Specify all files and parameters 2 If possible execute the task choose Apply to ensure that it will work 3 Choose Save Options from the File menu Specify a task specification file INTREPID will add the extension job INTREPID will create the file with the settings current at the time of the Save Options operation For full instructions on creating and editing task specification files see INTREPID task specification job files R06 gt gt To use a task specification file in an interactive Spectral Domain Grid Filters session Load the task specification job file File menu Load Options modify any settings as required then choose Apply gt gt To use a task specification file for a batch mode Spectral Domain Grid Filters task Type the command gfilter exe with the switch batch followed by the name and path if necessary of the task specification file For example if you had a task specification file called surv329 job in the current directory you would use the command gfilter exe batch surv329 job 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 32 Library Help Top 4 Back gt Task specification file example and notes OldGridFFT Here is an example of a Spectral Domain Grid Filters task specification file Process Begin Name GridFilter Input disk1 survey mlevel_grid Output disk1 survey vd_gridl Parameters Be
4. 5 Choose OK 6 If you turned on Regenerate data gaps INTREPID will need to refer to the original spatial domain dataset to locate them It displays the Open original dataset for gap generation dialog box Specify the original spatial domain input dataset If you wish only to examine the results of the pre filter transformation and you are therefore specifying an output dataset only as a formality turn off all check boxes This will speed up the pre filter transformation process See Previewing the transformed input dataset OldGridFFT below for further details about this technique The radially averaged power spectrum graph OldGridFFT Library Help Top See Power spectrum graphs in INTREPID spectral domain operations reference R14 for an introduction to power spectrum graphs Viewing the power spectrum graph gt gt To view a radially averaged power spectrum graph of the input and output datasets with the current filter selection Choose Radial Power Spectrum from the Window menu Mag Field Window Heie Main FFT Radial Power Spectr 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 8 Library Help Top lt 4 Back gt INTREPID displays the Spectral Domain Grid Filters Spectrum window containing the graph Intrepid Grid Filter tool V3 1 Beta File Gradients Reductions Continuations Complex Standard Directional Mag Field Window He
5. GridFFT T38 21 Library Help Top 4 Back gt Cosine Rolloff Filter OldGridFFT Here is an illustration of the effect of a cosine rolloff filter with the Pass option selected 9 3 11 0 12 7 14 4 16 1 0 0 0 7 1 3 1 9 2 6 3 2 3 9 4 5 5 1 5 8 6 4 7 0 7 7 8 3 9 0 9 6 10 2 If you choose Cosine Rolloff from the Standard menu INTREPID displays the Cosine Rolloff Parameters dialog box Low High Cutoff Degree cy m cy m pass reject Edit the parameters as required and choose OK See Cosine rolloff filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Unit Default value Butterworth Filter OldGridFFT If you choose Butterworth from the Standard menu INTREPID displays the Butterworth Filter Parameters dialog box Central Wavenumber Degree cy m pass reject Edit the parameters as required and choose OK Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 22 Library Help Top 4 Back gt See Butterworth filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Unit o Default value Gauss Filter OldGridFFT If you choose Gauss from the Standard menu INTREPID displays the Gauss Filter Parameters dialog box Standard Dev
6. INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 1 Library Help Top lt 4 Back gt Old spectral domain grid filters OldGridFFT T38 TP Note We have created a new spectral domain grid filters tool GridFFT See Spectral Domain Grid Filters GridFFT for details This chapter refers to the old version of the tool Only use this chapter if you particularly want to refer to this older version You can use the INTREPID Spectral Domain Grid Filters to enhance a grid dataset by enhancing features so that you can analyse them to better effect correcting the measured position of features removing irrelevant features patterns or noise in the grid INTREPID Spectral Domain Grid Filters can Prepare and transform your grid dataset from the spatial domain to the spectral domain Apply a range of geophysical directional noise removal and wavenumber dependent filters It can apply filters singly or combine as many as you wish Transform your grid dataset back to the spatial domain INTREPID spectral domain operations OldGridFFT For full details of spectral domain operations and the spectral domain filters provided with INTREPID see INTREPID spectral domain operations reference R14 Using the Spectral Domain Grid Filters tool OldGridFFT Library Help Top gt gt To use Spectral Domain Grid Filters with the INTREPID graphic user interface 1 Choose FFT_Filter from the Filter menu of t
7. Pre Filter and Post Filter Transformations separately on a dataset 1 Specify the input and output datasets with the pre filter and post filter processes you require See Specifying Input and Output Filtered Datasets OldGridF FT Pre Filter Transformation OldGridFFT and Post Filter Transformation OldGridF FT above for details 2 Choose Apply without having chosen any grid filters INTREPID will perform the pre filter and or post filter processes you have specified saving the results to the output dataset Help OldGridFFT You can use the Help menu to display help text on the topics shown in the menu illustration below Window Help Gradients gt Low Pass a High Pass 6 Band Pass Cosine Rolloff Displaying options and using task specification files OldGridFFT Displaying options OldGridFFT You can view a list of the filters selected in the status area at the bottom of the Spectral Domain Grid Filters main window Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 31 Library Help Top lt 4 Back gt Using task specification files OldGridFFT Library Help Top You can store sets of file specifications and parameter settings for Spectral Domain Grid Filters in task specification job files gt gt To create a task specification file with the Spectral Domain Grid Filters tool
8. REPID spectral domain operations reference R14 INTREPID exploits the symmetry in the spectral domain transformed data to achieve this You can examine the spectral domain grids using visualisation tools in the same way as you would a spatial domain grid INTREPID stores the transformation parameters in a text file with the same name as the input dataset and the extension fft It stores these files in the same directory as the input dataset See Fourier transform grid header files OldGridFFT below for details Fourier transform grid header files OldGridFFT Library Help Top When you transform a grid to the spectral domain INTREPID records information about the transformation in the Fourier transform grid header file This is an INTREPID auxiliary file with the extension fft It contains an fftdata Begin fftdata End block with a coefficient list and parameter values describing the transformed grid The file contains information that INTREPID is unable to record in the ERMapper compatible ers header file Here is an example of the file fftdata Begin coeff 1972 614766 0 006298246813 0 01090308443 0 0 0 0 0 0 0 m_extend 0 n_ extend 0 o numx 150 o numy 150 window 0 fft direction r comment Detrend Expand Fill Ffft CNDN Rfft Red Bool fftdata End Contact our technical support service if you require information about these files See Grid dataset file and directory structure in IN
9. REPID spectral domain operations reference R14 for an explanation of these options Turn on Save FFT for repeated processing if You will be performing another filter process in a subsequent Spectral Domain Grid Filters session or You wish to save the spectral domain version of the dataset for some other reason See Storing the transformed input dataset for later use OldGridFFT below for details Choose OK You can use the pre filter transformation for general processing of datasets See Other uses of the pre filter and post filter transformations OldGridFFT below for details 2012 Intrepid Geophysics 4 Back gt Library Help Top INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 6 Library Help Top q Back gt Storing the transformed input dataset for later use OldGridFFT After INTREPID completes the pre filter transformation it can retain the transformed input dataset for repeated grid filter processes If you wish to retain the transformed dataset for filtering on another occasion turn on the Save FFT For Repeated Processing check box INTREPID stores the results of the pre filter transformation process as a grid dataset The name of the dataset is the name of the input dataset with FFT appended to it These spectral domain grids have the same number of rows and columns as the expanded spatial domain grids before the transformation See Expanding the data area in INT
10. TREPID database file and data structures R05 and INTREPID Auxiliary files in INTREPID database file and data structures R05 for general information about the corresponding topics 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 7 Library Help Top q Back gt Post Filter Transformation OldGridFFT After you specify an output dataset INTREPID displays the Post Filter Transformation dialog box Intrepid Grid Filter tool V3 1 Beta Reverse FFT options required for output dataset f Reverse transform Wi Reduce data set m Regenerate data gaps _ Reproduce trend gt gt To specify post filter transformation 1 Ifyou wish to transform the dataset from the spectral to the spatial domain turn on Reverse transform 2 Ifyou wish to reduce an expanded dataset to its original size turn on the Reduce dataset See Reducing the dataset in INTREPID spectral domain operations reference R14 for information 3 Ifyou wish to restore to null the interpolated values in a dataset turn on the Regenerate data gaps See Regenerating the data gaps in INTREPID spectral domain operations reference R14 for information 4 Ifyou wish to replace the mean and restore any trend in the dataset that you had previously removed turn on Reproduce trend See Reproducing the trend in INTREPID spectral domain operations reference R14 for information
11. TREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Unit Default value b near surface slope a h near surface y intercept 1 B regional slope i H regional intercept 1 General Symmetric Filter OldGridFFT If you choose General Symmetric from the Standard menu INTREPID displays the General Symmetric Filter Parameters dialog box Edit the parameters as required and choose OK See General symmetric filter reference in INTREPID spectral domain operations reference R14 for information about this filter Library Help Top 2012 Intrepid Geophysics q Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 24 Library Help Top 4 Back gt Parameters Parameter Unit Default value Wavenumber increment frequency increment 0 001 Filter coefficients 8 1 1 1 1 0 8 0 5 0 2 O This isa low pass filter with a rolloff Directional Filters OldGridFFT See Directional Filters in INTREPID spectral domain operations reference R14 for information about these filters gt gt To apply Directional filters 1 Choose Pass or Cosine from the Directional menu pass INTREPID displays the corresponding parameters dialog box 2 Edit the parameters as required and choose OK Directional Pass Filter OldGridFFT Here is an illustration of the effects of a directional pass filter m Library H
12. agnetic reference field in INTREPID R15 Automatic calculation of field data OldGridFFT gt gt To automatically calculate the core magnetic field data from the AGRF or IGRF model 1 Choose AGRE or IGRF from the Mag Field menu Mag Fieid Window INTREPID displays the Enter Date and Sensor Height dialog box Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 13 Library Help Top Library Help Top 4 Back gt 2 Enter the date and height in the form of four numbers day month year height for example 12 10 92 60 0 represents 12 October 1992 and 60 0 metres Choose OK 3 INTREPID will automatically obtain the latitude and longitude of the mid point of the dataset 4 INTREPID will calculate the core magnetic field strength inclination and declination then display them in a message box Message Field 59661 9 nT inclination 567 4 deg declination 4 0 deg 5 Note the values if required INTREPID will automatically retain the values and use them As default parameters for Reduction filters As fixed parameters for the Pseudo Gravity and Susceptibility filters 6 Choose OK Parameters Date dd mm yy 31 12 92 Values automatically calculated and reported by INTREPID Paramar Ut Latitude A Longitude mimin Peis Field Intensity 2012 Intrepid Geophysics 4 Back gt INTREPID User M
13. andard menu INTREPID displays the High Pass Parameters dialog box Edit the parameter as required and choose OK See Filters for frequency ranges pass filters in INTREPID spectral domain operations reference R14 and specifically High pass filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Unit Default value Cutoff wavenumber cutoff frequency peyclesim O00 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 20 Library Help Top lt 4 Back gt Band Pass OldGridFFT Here is an illustration of the effect of a band filter with the Pass option selected 16 1 0 0 0 7 1 3 1 9 2 6 3 2 3 9 4 5 5 1 5 8 6 4 7 0 7 7 8 3 9 0 9 6 10 2 If you choose Band Pass from the Standard menu INTREPID displays the Band Pass Parameters dialog box Low High Cutoff cy m cy m pass reject Edit the parameters as required and choose OK See Filters for frequency ranges pass filters in INTREPID spectral domain operations reference R14 and specifically Band pass filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Unit Default value Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters Old
14. anual Old spectral domain grid filters OldGridFFT T38 14 Library Help Top 4 Back gt Manual specification of field data OldGridFFT gt gt To manually specify inclination declination and strength 1 Choose Manual from the Mag Field menu Mag Fieid Window Enter inclination declination and field intensity deg deg nT 2 Enter the Inclination Declination and Field Intensity in the text box separated by spaces then choose OK Parameters Parameter Unit Default value Inclination a Declination Field Intensity Derivative filters gradient filters OldGridFFT INTREPID provides a vertical derivative vertical gradient filter and horizontal derivative filters with respect to the Easterly direction Horizontal X Derivative and the Northerly direction Horizontal Y Derivative You can specify a fractional order for the vertical derivative See Single derivative filters in INTREPID spectral domain operations reference R14 for information about this filter gt gt To specify a Derivative gradient filter 1 Choose one of the options from the Gradients menu File Reductions aaen Y north 11 4 9 8 8 2 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 15 Library Help Top lt 4 Back gt 2 If you choose Vertical INTREPID displays the Order of Differentiation dialog bo
15. e filter again from its menu INTREPID will remove the filter and turn off the check mark in the menu If you have already applied the current set of filters the previous output power spectrum graph will remain in the display as well as the spectrum of any new filter results gt gt To remove all filter specifications Choose Clear Filter INTREPID will clear all filter specifications and all output power spectrum curves but retain your input output dataset selection and pre and post filter transformation specifications gt gt To modify a filter specification Remove the filter see above then respecify 1t with the new parameters Specifying parameters in Spectral Domain Grid Filters dialog boxes OldGridFFT The Spectral Domain Grid Filters dialog boxes generally have a single text box for parameters even if there are several of them gt gt To enter a number of parameters in a single text box Separate the parameters with spaces and ensure that they are in the order required Here is an example of a dialog box with a number of parameters Lat lon 34 130 Enter date sensorheight dd mm yy m 31 12 92 0 0 zl Frequency units and the Spectral Domain Grid Filters tool OldGridFFT The INTREPID power spectrum graphs display frequency scale in cycles km The Spectral Domain Grid Filters tool uses cycles m for cutoff frequencies in its dialog boxes If you use the power spectrum graph to assist you in choosing a cutoff f
16. elp Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 25 Library Help Top lt 4 Back gt If you choose Pass from the Directional menu INTREPID displays the Directional Pass Parameters dialog box pass reject Edit the parameters as required and choose OK See Directional pass filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parametric vat Toveuoene E masm OOOO e Pass Rj Passos the data ton Law and ineo Pass Directional Cosine Filter OldGridFFT Here is an illustration of the effects of a directional cosine filter Fi Intrepid Grid Filter tool V3 1 Beta File Gradients Reductions Continuations File Gradients Reductions Continuations Complex Standard Directional Mag Field Window Help Standard Directional Mag Field Window Heip Input spectrum Filter response Filtered spectrum Status Filtering done Selected filter s DCOS Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 26 Library Help Top lt 4 Back gt If you choose Cosine from the Directional menu INTREPID displays the Directional Cosine Parameters dialog box Filter Direction Degree of cosine deg pass reject Edit the parameters as required and choose OK See
17. filters OldGridFFT T38 18 Library Help Top lt 4 Back gt gt gt To specify a Standard filter 1 Choose one of the options from the Standard menu Complex Standard Directional Mag Field Window Low pass High pass Band pass Cosine rolloff Butterworth Gauss INTREPID displays a dialog box for entering parameters 2 Edit the parameters as required and choose OK Low Pass OldGridFFT Here is an illustration of the effect of a low pass filter If you choose Low Pass from the Standard menu INTREPID displays the Low Pass Parameters dialog box cutoff cy m Edit the parameter as required and choose OK See Filters for frequency ranges pass filters in INTREPID spectral domain operations reference R14 and specifically Low pass filter reference in INTREPID spectral domain operations reference R14 for information about this filter Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 19 Library Help Top lt 4 Back gt Parameters Cutoff wavenumber frequency 99999 High Pass OldGridFFT Here is an illustration of the effect of a high pass filter 12 7 11 0 9 3 7 6 5 9 4 2 o 2 5 g 0 8 0 9 2 6 4 32 6 0 7 7 9 3 11 0 12 7 14 4 o e 07 613 i9 26 32 39 45 51 58 64 70 7 7 83 90 3 6 10 2 If you choose High Pass from the St
18. gin Date 31 12 92 0 0 Elevation 0 Inclination Declination FieldStrength Detrend Yes DetrendValue 1 GridFill Yes GridExpand Yes MaxEntropy No ReverseFFT Yes Reduce Yes Regenerate No Trend No CosineBell Yes Hanning No Hamming No Blackman No Triangular No saveFFTbs Yes Filter Begin Type VERTICAL Order 75 Filter End Parameters End Process End Notes OldGridFFT e To specify a different input grid for regenerating the data gaps insert an Input_Orig line before the Parameters Begin End block For example looo O O O Input_Orig diskl survey raw_grid You can specify a compound filter by adding Filter1 Begin End Filter2 Begin End blocks after the original Filter Begin End block For example the filter blocks could be as follows Filter Begin Type VERTICAL Order 75 Filter End Filterl Begin Type UPWARD Order 100 Filterl End Library Help Top 2012 Intrepid Geophysics 4 Back gt
19. grid filters OldGridFFT T38 27 Library Help Top 4 Back gt 2 Choose Pseudo Gravity from the Complex menu INTREPID displays the Pseudo Gravity Parameters dialog box Ratio of susceptibility density contrast altitude separation SI SI m 3 Edit the parameters as required and choose OK See Pseudo gravity transformation reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Paame Ut peeve wams p omms e wame e o Sson Desy o ooo anaesoma fm Susceptibility filter OldGridFFT Here is an illustration of the effect of the Susceptibility filter 16 1 0 0 0 7 1 3 1 9 26 32 39 45 51 58 64 70 7 7 83 90 9 6 10 2 gt gt To specify a Susceptibility filter 1 Make sure you have specified the core magnetic field direction and intensity for the survey See Specifying the Earth s core magnetic field direction and intensity OldGridFFT above for instructions INTREPID will automatically use these values for the filter 2 Choose Susceptibility from the Complex menu INTREPID displays the Susceptibility Parameters dialog box Depth Latitude for Amplitude Limit dimension of prism m deg m Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 28 Library Help Top lt 4 Back gt 3 Edit the parameters as required and choose OK See Susceptibility filte
20. he Project Manager or use the command gfilter exe INTREPID displays the Spectral Domain Grid Filters Main window 2 Ifyou have previously prepared file specifications and parameter settings for Spectral Domain Grid Filters load the corresponding task specification file using Load Options from the File menu See Specifying Input and Output Filtered Datasets OldGridFFT below for detailed instructions If all of the specifications are correct in this file go to step 9 If you wish to modify any settings carry out the following steps as required 3 Specify the grid dataset to be processed Use Open Input from the File menu See Specifying Input and Output Filtered Datasets OldGridFFT below for detailed instructions 4 Ifthe input data is in the spatial domain INTREPID displays the Pre Filter Transformation dialog box Specify the pre filter transformation and options as required then choose OK See Pre Filter Transformation OldGridFFT below for detailed instructions 5 Specify the output grid dataset Use Specify Output from the File menu See Specifying Input and Output Filtered Datasets OldGridFFT below for detailed instructions INTREPID displays the Post Filter Transformation dialog box 6 Specify the post filter transformation and associated options as required then choose OK See Post Filter Transformation OldGridFFT below for detailed instructions 2012 Intrepid Geophysics 4 Back gt INTREPID Use
21. iation cy m pass reject Edit the parameters as required and choose OK See Gauss filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Unit Default value Pass Reject Pass Pass the lower frequencies Pass Matched Filter OldGridFFT Here is an example of a matched filter using the coefficients illustrated in the dialog box below Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 23 Library Help Top lt 4 Back gt gt gt To use the matched filter 1 Ifyou wish to enter the matched filter coefficients directly without INTREPID assisting you to calculate them go to step 5 2 View the power spectrum graph for the input dataset See The radially averaged power spectrum graph OldGridFFT above for instructions 3 Obtain and make a note of slope and y intercept readings for the regional line segment See The radially averaged power spectrum graph OldGridFFT above for instructions 4 Obtain and make a note of slope and y intercept readings for the near surface line segment 5 Choose Matched from the Standard menu INTREPID displays the Matched Filter Parameters dialog box Filter Coefficients b h near surface and B H regional 6 Edit the parameters as required and choose OK See Matched filter reference in IN
22. ing options and using task specification files OldGridFFT below for more information Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 5 Library Help Top q Back gt Pre Filter Transformation OldGridFFT After you specify an input dataset if the data is in the spatial domain INTREPID displays the Pre Filter Transformation dialog box Intrepid Grid Filter tool V3 1 Beta FFT options required for spatial dataset f Detrend dataset Degree of detrend ao Interpolate gaps Apply maximum entropy Spatial Filter Options yf Cosine bell _ Hanning _ Hamming _ Blackman _ Triangular f Save FFT for repeated processing gt gt To specify the pre filter transformation for a normal spatial domain dataset 1 5 Turn on Detrend dataset and change the Degree of Detrend parameter 1f required See Detrending data values in INTREPID spectral domain operations reference R14 for an explanation of this process Select the Interpolate Gaps or Apply Maximum Entropy option See Expanding the data area in INTREPID spectral domain operations reference R14 for information about the Interpolate Gaps and Apply Maximum Entropy options Turn on any edge region spatial filters that you require Cosine Bell Hanning Hamming Blackman Triangular See Damping of dataset edges before spectral transform in INT
23. lp 11 4 15 2 0 0 0 7 1 3 1 9 2 6 3 2 3 9 4 5 5 1 5 8 6 4 7 0 7 7 8 3 9 0 9 6 10 2 Natural Log radially averaged spectrum vs wn cy km Blue represents input spectrum imaa The input dataset power spectrum is shown in blue and the filtered dataset power spectrum in red gt gt To return to the Spectral Domain Grid Filters Main window Choose Main from the Window menu Querying the power spectrum graph OldGridFFT INTREPID can calculate and display the y intercept and the slope of the line joining any two points in the graph and the corresponding Spector Grant depth estimatet You can use the intercept and slope in the Matched filter See Matched Filter OldGridFFT below for details gt gt To display the y intercept and slope of the line joining any two points in the Power Spectrum graph and the corresponding Spector Grant depth estimate Click the two points INTREPID displays the data in a message box Message ge ib intercept 2 62 and h slope 4 50 km cy Spector Grant depth estimate 358 m gt gt To display an intercept slope depth estimate report for another pair of points Dismiss the message box if it is still present click once anywhere on the graph to release the previous line segment selection then click the two required points 1 Spector A and Grant F S 1970 Statistical methods for interpreting aeromagnetic data Geophysics 35 293 302 Library Help T
24. nse Filtered spectrum Status Filtering done Selected filter s DCOS Clear Fi 1ter INTREPID will perform the post filter transformation as specified and save the dataset If you specified that INTREPID will regenerate the data gaps existing before the pre filter transformation specify the original spatial domain input dataset when prompted by INTREPID See Post Filter Transformation OldGridF FT below for information If you wish to record the specifications for this process in a job file in order to repeat a similar task later or for some other reason use Save Options from the File menu See Specifying Input and Output Filtered Datasets OldGridFFT below for detailed instructions If you wish to repeat the process repeat steps 2 11 varying the parameters and or data files as required To exit from Spectral Domain Grid Filters choose Quit from the File menu After a Spectral Domain Grid Filters process is complete you can View a radially averaged power spectrum graph of the input and output datasets and Display slope y intercept and Spector Grant depth estimate for any straight line segment in the power spectrum graph 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 3 Library Help Top lt 4 Back gt To view these displays choose Radial Power Spectrum from the Window menu See The radially averaged power spectrum gra
25. on You can specify this copy of the dataset as input in future sessions and avoid unnecessary processing See Storing the transformed input dataset for later use OldGridF FT below for more information Open Input Dataset Use this option to specify the grid dataset to be filtered INTREPID will open the dataset file If the data is in the spatial domain INTREPID displays the Pre Filter Transformation dialog box See Pre Filter Transformation OldGridFFT below for further instructions Specify Output Dataset Use this option to specify the name for the grid dataset you are creating with this process INTREPID displays the Post Filter Transformation dialog box After you complete this dialog box INTREPID may require you to specify the original spatial dataset or other mask file as required See Post Filter Transformation OldGridFFT below for further instructions Load Options If you wish to use an existing task specification file to specify the Spectral Domain Grid Filters process use this option to specify the task specification file required INTREPID will load the file and use its contents to set all of the parameters See Displaying options and using task specification files OldGridF FT below for more information Save Options If you wish to save the current Spectral Domain Grid Filters file specifications and parameter settings as an task specification file use this menu option to specify the filename and save the file See Display
26. on degree of cosine function Pass Reject 9 U Un INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 12 Library Help Top lt 4 Back gt Menu Filter Type Parameters Required Complex Pseudo Inclination declination field intensity susceptibility density contrast ratio altitude separation Gravity Decorrugatio line spacing direction along striping n Apparent thickness of the Earth model Density Specifying the Earth s core magnetic field direction and intensity OldGridFFT If you wish to use a Reduction Susceptibility or Pseudo Gravity filters See Reduction Filters OldGridFFT Pseudo Gravity transformation OldGridFFT and Susceptibility filter OldGridFFT below you must specify the direction and strength of the Earth s core magnetic field at the mid point of the dataset You can use one of the following methods with corresponding options in the Mag Field menu Susceptibility Inclination declination field intensity depth of Map continuation latitude for amplitude limit dimension of prism Choose either the Australian or International Geomagnetic Reference Fields AGRE and IGRF and specify the survey date and sensor height INTREPID will calculate the core magnetic field data for you Manually specify the Earth s core magnetic field inclination declination and intensity for the mid point of the dataset For general information about the GRF see The geom
27. op 2012 Intrepid Geophysics q Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 9 Library Help Top lt 4 Back gt Clearing the power spectrum display OldGridFFT After applying a filter if you change the filter specifications and choose Apply again the previous output power spectrum graph may remain in the display as well as the spectrum of the new filter results This may continue happening until you clear all of the specifications See Specifying and removing grid filters OldGridFFT below for instructions Previewing the transformed input dataset OldGridFFT Before applying any filters you can view The colour display of the transformed input dataset in the Input Spectrum Display area and The Power Spectrum graph of the transformed input dataset gt gt To preview the transformed input dataset 1 Specify the input dataset with pre filter transformation as required by you 2 Specify an output dataset You may delete this at any time after the session 3 Turn off all check boxes in the Post Filter Transformation dialog box This will speed up the output part of the process which is not required for your purposes at this time 4 Choose Apply INTREPID will carry out the transformation and display the input dataset using pseudocolour in the Input Spectrum and Filtered Spectrum boxes You can examine the power spectrum graph by choosing the Radial Power Spectrum from the Windo
28. ph OldGridFFT below After using Spectral Domain Grid Filters you can carry out a more detailed inspection of the filtered grid using an INTREPID visualisation tool See Visualisation T26 You can choose options from the Help menu See Help OldGridF FT below You can execute Spectral Domain Grid Filters as a batch task using a task specification job file that you have previously prepared See Using task specification files OldGridFFT below for details Spectral Domain Grid Filters display OldGridFFT The Spectral Domain Grid Filters Main window has three spectrum display boxes Each box shows a spectrum for all directions The Input Spectrum box shows the spectrum of the input dataset in with energy shown using pseudocolour The input spectrum display box is a graph of frequency versus energy in Fourier space The colours represent the energy or amplitude of each frequency where red is high blue is low and black is zero energy The origin zero frequency occurs half way up the left side of the display and is typically coloured red or yellow The plot is symmetrical about this vertical edge which has the spatial orientation of North South The maximum frequency in the display is the Nyquist frequency for the data The frequency range zero to Nyquist is normalised to fit the input spectrum display box e Since the graph is radial strictly speaking you should view it as a semi circle rather than a
29. r reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Inclination Declination Field Intensity Depth of continuation Latitude for amplitude limit Dimension of prism Decorrugation OldGridFFT If you choose Decorrugation from the Complex menu INTREPID displays the Decorrugation Parameters dialog box Line Spacing Direction along Striping from North m deg Edit the parameters as required and choose OK See Decorrugation filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Unit Default value Direction Along Striping from North a 90 East West Apparent Density OldGridFFT Here is an illustration of the effects of an Apparent Density filter 16 1 0 0 0 7 1 3 1 9 2 6 3 2 3 9 4 5 5 1 5 8 6 4 7 0 7 7 8 3 9 0 9 6 10 2 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 29 Library Help Top lt 4 Back gt If you choose the Apparent Density from the Complex menu INTREPID displays the Apparent Density Parameters dialog box Thickness of the earth model m Edit the parameters as required and choose OK See Apparent density filter reference in INTREPID spectral domain operations reference R14 for information about this filter
30. r Manual Old spectral domain grid filters OldGridFFT T38 2 Library Help Top Library Help Top 10 11 12 13 q Back gt If you wish to examine the colour display of the input dataset after pre filter transformation in the Input Spectrum Display area and or the Power Spectrum graph before applying any filters choose Clear Filter then choose Apply INTREPID will carry out the transformation and display the input dataset You can examine the power spectrum graph of the dataset as described below See Previewing the transformed input dataset OldGridFFT below Use the filter menus and associated dialog boxes to select the filter options that you wish to use and specify their required parameters As you specify the filters INTREPID displays a colour representation of the effects of the filter combination in the Filter Response area of the Spectral Domain Grid Filters Main window See INTREPID spectral domain operations reference R14 and the sections following for detailed instructions Choose Apply INTREPID will perform the filter process and display the results of the filter in the Filtered Spectrum area of the of the Spectral Domain Grid Filters Main window x Intrepid Grid Filter tool V3 1 Beta File Gradients Reductions Continuations File Gradients Reductions Continuations Complex Standard Directional Mag Field Window Help Standard Directional Mag Field Window Heip Input spectrum Filter respo
31. requency for a filter divide the frequency by 1000 to convert it to cycles m before specifying it in the filter dialog box Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 11 Library Help Top 4 Back gt Summary of menus filters and parameters OldGridFFT This table contains a summary of the filters their variations and the menus in which you can find them Menu Filter Type Parameters Required Gradients Derivative Vertical order gradient X Kast Y North Reduction inclination declination Pole Pole dow Latitude Continuations level central wavenumber frequency degree of d rolloff cutoff wavenumber cutoff frequency Band Pass Pass Reject Cosine Pass inclination declination latitude for amplitude limit low and high cutoff wavenumbers frequencies low and high cutoff wavenumbers frequencies degree of cosine function Rolloff Reject Butterworth Pass Reject Gauss Reject General Symmetric Directional Directional Pass Directional Cosine Library Help Top Library Help Top 2012 Intrepid Geophysics 4 Back gt Intrepid Geophysics lt 4 Back gt Central wavenumber frequency degree of Butterworth filter standard deviation wavenumber frequency increment filter coefficients low and high cutoff angles Pass Reject filter directi
32. s a rectangle The Filter Spectrum box represents the weights of the current filter specification using pseudocolour After you apply a filter the Filtered Spectrum box shows the spectrum of the filter results with energy shown using pseudocolour The Spectral Domain Grid Filters Power Spectrum window contains a power spectrum graph for the most recently applied filter See The radially averaged power spectrum graph OldGridFFT below and Power spectrum graphs in INTREPID spectral domain operations reference R14 for information about this Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 4 Library Help Top lt 4 Back gt Specifying Input and Output Filtered Datasets OldGridFFT Before using any grid filters you must specify input and output datasets Choose the options as required from the File menu DES Gradients Reductions Open Input Dataset opecify Output Dataset Load Options save Options Quit In each case INTREPID displays an Open or Save As dialog box Use the directory and file selector to locate the file you require See Specifying input and output files in Introduction to INTREPID R02 for information about specifying files If you wish to apply Spectral Domain Grid Filters to a dataset on a number of occasions you can save a copy of the transformed version i e the spectral domain versi
33. tion about this filter 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 16 Library Help Top lt 4 Back gt Parameters Parameter Default value Inclination calculated or specified Declination calculated or specified Latitude for Amplitude Limit 20 standard 10 low latitude Reduction to the Equator OldGridFFT If you choose To Equator from the Reductions menu INTREPID displays the Reduction to the Equator Parameters dialog box Edit the parameters as required and choose OK See Reduction filters reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Continuation Filters OldGridFFT See Continuation filters reference in INTREPID spectral domain operations reference R14 for information about these filters gt gt To specify a Continuation filter 1 Choose Downward or Upward from the Continuations menu File Gradients Reductions Complex INTREPID displays the Level of Continuation dialog box 2 Edit the parameters as required and choose OK Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 17 Library Help Top 4 Back gt Upward Continuation OldGridFFT If you choose Upward from the Continuations menu INTREPID displays the Upward Continuation dialog bo
34. w menu If you have already applied filters and then wish to view the transformed input dataset without filters choose Clear Filter then Apply To speed up the process you could also respecify the output dataset with all post filter transformation options turned off The Spectral Domain Grid Filters OldGridFFT Information about filters and parameters OldGridFFT See Spectral domain filters available in INTREPID spectral domain operations reference R14 for a complete list of the filters available including a description and an explanation of the purpose of each parameter Specifying and removing grid filters OldGridFFT Library Help Top You can specify a number of filters for INTREPID to use in the Spectral Domain Grid Filters process INTREPID will apply the filters one after the other to the data when you choose Apply You can modify your filter selection as required gt gt To specify a filter for the Spectral Domain Grid Filters process 1 Choose the filter from its corresponding menu INTREPID displays a dialog box for you to specify the filter parameters 2 Specify the parameters and choose OK INTREPID places a check mark against each filter you select in its corresponding menu 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual Old spectral domain grid filters OldGridFFT T38 10 Library Help Top lt 4 Back gt gt gt To remove a filter from your filter selections Choose th
35. x Level of Continuation m Edit the parameter as required and choose OK See Continuation filters reference in INTREPID spectral domain operations reference R14 and specifically Upward Continuation filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Downward Continuation OldGridFFT If you choose Downward from the Continuations menu INTREPID displays the Downward Continuation dialog box Level of Continuation m Degree of rolloff 0 to 15 Median wave number for rol Level of Continuation m 7 Degree of rolloff 0 to 15 7 Median wave number for roll off cy m 50 0 5 0 005 Ok Cancel Edit the parameters as required and choose OK See Continuation filters reference in INTREPID spectral domain operations reference R14 and specifically Downward Continuation filter reference in INTREPID spectral domain operations reference R14 for information about this filter Parameters Parameter Unit Default value a Degree of Rolloff Median Frequency of Rolloff cycles m 0 005 Median Wavenumber of Rolloff Standard Filters for frequency ranges OldGridFFT See Filters for frequency ranges pass filters in INTREPID spectral domain operations reference R14 for information about these filters Library Help Top 2012 Intrepid Geophysics q Back gt INTREPID User Manual Old spectral domain grid
36. x Order of Differentation 3 Edit the parameter as required and choose OK Parameters Order of Differentiation Vertical derivative only _ jf 1 Reduction Filters OldGridFFT See Reduction filters reference in INTREPID spectral domain operations reference R14 for information about these filters gt gt To specify a Reduction filter 1 Ensure that you have specified the Earth s core magnetic field data See Specifying the Earth s core magnetic field direction and intensity OldGridFFT 2 Choose one of the options from the Reductions menu File Gradients BigCDUTsiiita Continuations Help To equator To pole To pole low latitude eS INTREPID displays a dialog box for entering parameters The dialog box will already contain as defaults the Earth s core magnetic field data that you have calculated or specified 3 Edit the parameters as required and choose OK Reduction to the pole standard and low latitude OldGridFFT Library Help Top If you choose To Pole or To Pole Low Latitude from the Reductions menu INTREPID displays the Reduction to the Pole Parameters dialog box Incl Decl Lat for Ampl Limit deg deg deg Edit the parameters as required and choose OK See Reduction filters reference in INTREPID spectral domain operations reference R14 and specifically Reduction to the Pole reference in INTREPID spectral domain operations reference R14 for informa
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