INTREPID spatial and time domain filters and transformations (R13)
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1. INTREPID spatial and time domain filters and transformations R13 13 lt 4 Back gt INTREPID User Manual Library Help Top Local mean median filters Mean Line Filter only Median Line Filter and Spatial Convolution Grid Filters only Local mean Tensor Profile Editor These filters adjust the value of the target HEH cell based on the mean or median value of the cell and its neighbours in a window For line data this window is a number of data points surrounding the target point For grid data the window is square with the target cell in the centre The standard Local Mean and Local Median filter dialog boxes appear below Median Filter Properties Convolve Transform Filter Properties Convelys GEG om EF Convolve Filter Properties Filter Name Median Filter Name LocalMean_tensor Filter Space SPATIAL Filter Space SPATIAL Filter Properties Filter Window Length OO OO O O Extend D ata U sing Median Filter Properties Convolve Filter Properties Fiter Name Filter Space SPATIAL Filter Properties Filter Window Length 5 Extend D ata U sing en Filter Properties Filter Window Length Low Pass C Zero Pad C Zero Pad C Mirror Pad Data Flipped Mirror Pad Data l Output Residuals V Replace trend in Output Accept Cancel C Mirror Pad Data Flipped Mirror Pad Data l Output Residuals V Replace trend in Output Accept Cancel C High Pass Extend D2. INTREPID shows this as Spatial 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 4 Library Help Top lt 4 Back gt Detrending and replacing trends Before applying a filter INTREPID removes first order trends overall slope in the data If it makes sense to restore the trend after application of the filter INTREPID will either automatically replace the trend or include a Replace Trend option in the filter properties dialog box INTREPID will normally replace the trend unless you turn off the Replace Trend check box Creating the extended region for filters To prevent loss of data at the line ends filters use an extended region at each end of the line where the values of the first or last original data point can be rolled off to zero This is particularly important for the Fuller filter Hilbert transform and Phillips auto depth estimation The properties dialog boxes for these filters contain parameters for specifying the extended region Hilbert Transform Filter Properties Hilbert Filter Properties Filter Space HILBERT Filter Properties Filter Window Length 301 Extend D ata U sing Zero Pad C Mirror Pad Data Flipped Mirror Pad Data Output Options Hilbert C Complex Amplitude Instantaneous Phase Phase Unwinding Options Instantaneous Phase unwound C Instantaneous Frequency Phase Unwi
3. a Fuller filter for the second low pass filter process in Decorrugation 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 11 Library Help Top lt 4 Back gt Parameters Window Size standard parameter name Streak Width m in Decorrugation first high pass filter Streak Length m in Decorrugation second low pass filter Secondary filter along correction m in Microlevelling The window size corresponds to the maximum width of anomalies to be identified as high frequency In the Decorrugation and Microlevelling tools this is measured in metres In the other tools it is measured as the number of line dataset data points In spectral terms the window size corresponds to a cutoff wavelength for the filter Thus 1 window size corresponds to the cutoff frequency The minimum window size is 2 so the maximum frequency is 1 2 or 0 5 Thus frequencies range from 0 to 0 5 and the cutoff frequency lies within this range Minimum amplitude Tolerance fixed in Microlevelling change in Decorrugation task specification files only When calculating the Naudy filter result INTREPID will ignore changes with amplitude less than the value of this parameter Specify the Tolerance in Signal units or grid cell units The tolerance corresponds to the minimum amplitude of anomalies to be identified as high frequency data INTREPID will identify an anomaly
4. 4 Back gt Availability in INTREPID tools The following table shows the filters and transformations used in each INTREPID tool The notation Y indicates that the tool uses the filter or transformation Availability of spatial filters in IS INTREPID tools D pa O cx pa 2 5 2 E 2 g g JE c IS S O x g c 5 Q xe i D c c amp a fe 2 2 c o o es 5 X lo IC e 3 JE g g e E ls Ble lg oi B 52 j ll EJIE elg 5 2 gig g gls lz ls El 7 Ss r gt e Ka D ul Z it O 4a J jt O JI A A Profile Editor Y Y Y Gridding Y Y Y Y Levelling crossovers calculation Y Y Line Filter Y IY JY Y IY Y IY Y Y Decorrugation Y Y Microlevelling Y Y Spatial Convolution Grid Filters Y Y Y Y Y Equivalent Layer Y Isostatic Y Spectral grid filtering Y Y Y Spectral Voxet filtering Y Y The local mean filter is available as one of the user defined kernels The filters listed in this section carry one or two icons denoting whether they are available in the Spectral Domain Grid Filters tool and or the Line Filter tool EE This icon indicates that the filter is available for use with line datasets This icon indicates that the filter is available for use with grid datasets Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial an
5. D Example of a convolution kernel definition file Kernel Begin Name hz13_ 2nd deriv Description HZ13 2nd Derivative Type Convolution Rows 3 Columns 3 OkOnSubsampledData FALSE Array 0 500000 2 000000 0 500000 2 000000 6 000000 2 000000 0 500000 2 000000 0 500000 Scalefactor 1 Kernel End Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 9 Library Help Top Fuller filter Parameters Library Help Top 4 Back gt Gridding Levelling Line Filter Decorrugation Microlevelling tools The moving average Fuller convolution filter detects high frequency data and passes or rejects it See User defined convolution kernels for a general explanation of convolution filters INTREPID can apply the Fuller filter to line or grid data The standard Fuller filter dialog box appears below Convolve Transform Filter Properties Convolve Filter Properties Filter Name Fuller Filter Space SPATIAL Filter Properties Filter Window Length 5 Low Pass High Pass Extend D ata U sing C Zero Pad C Mirror Pad Data Flipped Mirror Pad Data M Normalize Filter Weights M Output Residuals M Replace trend in Output Accept Cancel Window Size data points standard parameter name Streak Width m in Decorrugation first high pass filter Streak Length m
6. Grid Filters only The Contrast Normalisation filter is a non linear space variant stretch filter that will enhance the low amplitude high frequency content and dampen the high amplitude content It has a similar effect to an automatic gain control filter See Automatic gain control and contrast normalisation The Contrast Normalisation filter dialog box appears below CNorm Filter Box Window Mean Stddev Weight_for_means MaxG ain _OK Cancel Parameters Window Use this text box to specify the width of the filter window For example if the width of the filter window is 21 then the new target cell value will be calculated from the value of the cell and its 10 neighbours in all directions Mean Use this text box to specify the desired mean of the output Stddev Use this text box to specify the desired standard deviation of the output Weight for Means Use this text box to specify the weighting to apply to the desired mean versus the local mean of the window The closer the weighting to 0 the more biassed result will be towards the local mean of the window If the weighting is equal to 0 the filter will use the local mean of the window and ignore your desired mean The closer the weighting to 1 more biassed the results will be towards the desired mean If the weighting is equal to 1 the filter will use your desired mean and ignore the local mean of the window Essentially this has the effect of dampening reg
7. INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 lt 4 Back gt Library Help Top INTREPID spatial and time domain filters and transformations R13 INTREPID tools use a range of filters and transformations in the spatial and time domains This appendix summarises the filters and transformations and gives details about their parameters Some tools allow you to change parameters whereas for other tools their values are fixed This appendix shows which parameters may be set for each tool See the chapter corresponding to the tool for further details about this INTREPID tools use the following spatial time filters and transformations 2012 Intrepid Geophysics 4 Back gt Library Help Top User defined convolution kernel Fuller filter Naudy filter 4th difference function Gradient Automatic gain control Contrast normalisation Hilbert transform Phillips auto depth estimation Gravity Inversion Strip gravity layer Butterworth Recursive RC filter Hilbert Pair convolutions for Falcon Spectral derivatives and integrations Quaternions as a linear method for manipuating and filtering rotations 2d 3d complex tensor filters Infinite Impulse and Finite impulse methods are used as required Isostatic correction uses the Bessel function integral INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 2 Library Help Top lt
8. These functions are in a form that is independent of magnetic inclination and dip Depth estimates are calculated using combinations of autocorrelation functions at various lags Consistent depth estimates using a range of different lags are interpreted to mean a valid depth estimate The best results occur when the window length matches the wavelength of the magnetic responses INTREPID expresses the results in the same units as the X and Y fields of the dataset Depth Estimate values are negative numbers with 0 corresponding to the survey height See also Querying the power spectrum graph OldGridFFT in Old spectral domain grid filters OldGridFFT T38 for information about the Spector Grant depth estimation method used in the spectral domain See also Naudy Automatic Model interpretation T43 and Euler Deconvolution T44 for further depth estimation techniques The standard Phillips Automatic Depth Estimation dialog box appears below Phillips Auto Depth Properties Phillips Auto Depth Properties Fiter Name Phillips_Auto_Depth Filter Space SPATIAL Filter Properties Filter Width m_ 290 Depth Tuning factor 0 1 0 9 Extend D ata U sing C Zero Pad C Mirror Pad Data Flipped Mirror Pad Data Accept Cancel Parameters Filter width m The filter width must correspond to the maximum magnetic basement depth sought The default value is 290 m Depth tuning factor Use this to vary the primary and se
9. ain filters and transformations R13 22 Library Help Top lt 4 Back gt Strip Gravity Layer Line Filter only A simple filter to calculate the gravitational effect of a layer of variable thickness It is based upon using the formula for the gravitational effect for a Prism Parameter input Zbot Depth to bottom of layer Ztop Depth to top of layer default is 0 0 De Density contrast gm cc Library Help Top 2012 Intrepid Geophysics lt 4 Back gt
10. alue is 19 1 e 9 points on each side of the target point The value of parameter cannot be less than 9 Output Options Quadrature This is the imaginary component of the input signal derived using the Hilbert transform The Hilbert Transform includes a detrending process You can choose whether to replace the trend in the filter results using the two Quadrature options Quadrature local trend replaced Quadrature local trend removed Even though the Hilbert transform is not connected with the spectral domain you can find a relevant discussion of detrending in section Detrending data values in INTREPID spectral domain operations reference R14 Complex Amplitude This is the magnitude of sum of the input data real component and the Quadrature results imaginary component P Deo os 2 complex amplitude preal imaginary Library Help Top 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 17 Library Help Top lt 4 Back gt Instantaneous Phase This is derived by combining the input data real component and the Quadrature results imaginary component using the formula masina real instantaneous phase atan Instantaneous Phase can show continuity for subtle features often lost when you only examine the real component See the articles Taner Koehler and Sheriff 1979 and Fitzgerald Yassi and Dart 1997 for furth
11. and transformations R13 6 Library Help Top 4 Back gt User defined convolution kernels Library Help Top Line Filter Spatial Convolution Grid Filters Equivalent Layer only When you apply a convolution filter INTREPID replaces the Signal value of each data point line datasets or each grid cell grid datasets with a weighted combination of its original value and those of its neighbours using a set of coefficients A user defined convolution kernel contains a set of coefficients In an INTREPID revision to be released soon you will be able to apply user defined convolution kernels to line datasets using the Line Filter tool See Filter operations in Line Filtering T31 In the current version of INTREPID you can apply user defined convolution kernels to grid datasets using the Spatial Convolution tool See Spatial Convolution Grid Filters T34 The Weiner Filter tool automatically produces kernels for grid datasets The Equivalent Layer tool uses these kernel for its operation See Creating Weiner convolution kernels T35 and Equivalent Layer corrections T36 for details 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 7 Library Help Top 4 Back gt User defined grid kernels supplied with INTREPID The following table describes the predefined convolution kernels typically supplied with INTREPID Many o
12. as high frequency if it has amplitude higher than the tolerance you specify The default value 0 1 corresponds to 0 1 nT the current documented accuracy of magnetometers This ensures that INTREPID will not waste time attempting to smooth out the normal fluctuations associated with the precision limits of the instrument Wavelength Profile Editor When calculating the Naudy filter result INTREPID will only examine sequences of data points up to the Wavelength as potential noise Naudy filter high low output options Fixed in Profile Editor high pass Levelling low pass Decorrugation high pass then low pass Microlevelling low pass Notch output only available in Line Filter and Gridding You can specify whether a Naudy filter will output The data identified as high frequency High Pass The data with the high frequency component removed Low Pass The data within a band notch or range of frequencies related to the window size Notch The data outside a band notch or range of frequencies related to the window size Notch with Output Residuals turned on Select the option corresponding to your requirement To apply the band notch option INTREPID applies a high pass Naudy filter then a low pass to the results This outputs or rejects data with frequency close to the specified cutoff frequency of the filter 1 INTREPID normally uses a Naudy filter for the first high pass filter process in Decorrugat
13. ata U sing C Zero Pad C Mirror Pad Data Flipped Mirror Pad Data Normalize Filter Weights M Output Residuals Replace trend in Output OK Cancel Parameters Window length Use this text box to specify the width of the filter window For example if the width of the filter window is 21 then the new cell value will be calculated from the value of the cell and its 10 neighbours in each direction Line data 10 data points on either side of the target point Grid data block of cells 10 x 10 with target cell in the centre The value of parameter cannot be less than 3 Low Pass High Pass Contact technical support for information Normalise filter weights Contact technical support for information Output Residuals fixed in Spatial Convolution Grid Filters turned off If you turn on this check box INTREPID will output the difference between the filter results and the original data Replace trend in output fixed in Spatial Convolution Grid Filters turned on Before applying the local mean median filter INTREPID removes first order trends overall slope in the data If this check box is on this is the default condition INTREPID will restore this trend after the filter process Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 14 Library Help Top lt 4 Back gt Local Maximum filter The local maximum filt
14. condary depth estimate quality of fit criteria INTREPID will multiply the criteria by the factor you specify 1 Phillips Jeffrey D 1979 ADEPT A program to estimate depth to magnetic basement from sampled magnetic profiles Reston Virginia U S Geological Survey Open File Report 79 367 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 19 Library Help Top lt 4 Back gt Lacoste RC filter Line Filter and Profile Editor compound data filters The Lacoste RC Resistive Capacitive filter was originally designed using analog circuits for filtering very noisy marine data Its digital equivalent can be used to filter stabilised platform monitor data which contains a great deal of high frequency noise from the movement of the ship acquiring data Some properties of the Lacoste filter are The filter is highly linear The filter leaves a local trend in the data The first 3 stages of the filter compensate for the acquisition instrument phase lag In the case of the LaCoste and Romberg S meter the firmware performs 3 stages of 20 second forward lag filtering only The Lacoste filter compensates for this by performing 3 stages of 20 second reverse lag only Successive filter stages are then run in pairs to eliminate any phase lag LaCoste Transform Filter Properties LaCoste RC Filter Properties Originally designed for ver
15. d time domain filters and transformations R13 3 Library Help Top 4 Back gt Standard spatial time filter transformation dialog boxes Filter name Filter space Library Help Top Some INTREPID tools now use a standard dialog box to configure each filter or transformation With new versions of INTREPID more tools will use these standard dialog boxes as appropriate A typical standard spatial time filter transformation dialog box appears below Convolve Transform Filter Properties Convolve Filter Properties Filter Name Fuller Filter Space SPATIAL Filter Properties Fiter Window Length Low Pass C High Pass Extend D ata U sing C Zero Pad Mirror Pad Data Flipped Mirror Pad Data V Normalize Filter Weights F Output Residuals Replace trend in Output Accept Cancel Certain features are common to all of these dialog boxes as described in the following sections For standard INTREPID filters and transformations configured directly in interactive or batch mode the Name text box shows the filter type In the Line Filter tool for filters configured using a filter definition file the Name text box shows the name of the filter definition file ahd is used for saving the filter specifications See Standard filter names in Line Filtering T31 and Loading and saving filter definitions in Line Filtering T31 for details For spatial and time domain filters and transformations
16. e data with the high frequency component removed Low Pass Select the option as required Output residuals This option reverses the action of the High Pass Low Pass options above If you turn it on INTREPID will reject the data that it would normally pass and pass the data it would normally reject according to these options Replace trend in output fixed in Profile Editor Levelling Decorrugation Microlevelling all turned on Before applying the Fuller filter INTREPID removes first order trends overall slope in the data If this check box is on this is the default condition INTREPID will restore this trend after the filter process Profile Editor Gridding Levelling Line Filter Decorrugation Microlevelling tools This filter detects sudden changes in your data i e high frequency data These may be due to noise or spikes that are not characteristic of potential field data The Naudy filter is commonly used for eliminating noise and spikes The standard Naudy filter dialog box and the parameters box from the Profile Editor appear below Convolve Transform Filter Properties Naudy non linear Filter Properties Filter Space SPATIAL Filter Properties Filter Window Length 5 Minimum Amplitude Low Pass C High Pass C Notch Naudy Filter Parameters Tolerance Z Units Wavelengths Data Points LJ l Output Residuals V Replace trend in Output Accept Cancel 1 INTREPID normally uses
17. er discussion of this technique Unwound Instantaneous phase results have data jumps due to the spiralling nature of the filter INTREPID can correct this using a surface consistent partial unwrapping algorithm Select this option to produce unwrapped instantaneous phase results Instantaneous Frequency This is a measure of change in the Instantaneous Phase see previous section comparing adjacent values of Instantaneous Phase results It uses the formula instantaneous frequency diff1 instantaneous phase See DIFF function example in INTREPID expressions and functions R12 for an illustration of this function 1 Taner M T Koehler F and Sheriff R E 1979 Complex seismic trace analysis Geophysics 44 1041 1063 2 Fitzgerald D Yassi N and Dart P 1997 A case study on geophysical gridding techniques INTREPID perspective Exploration Geophysics 28 1 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 18 Library Help Top 4 Back gt Phillips automatic depth estimation Library Help Top Line Filter only The Phillips method estimates from the Signal field signal the depth to a magnetic basement It assumes a 2 D magnetic basement can be approximated by an assemblage of thin vertical or near vertical dykes It uses autocorrelation functions of magnetic anomalies due to such dykes
18. er operates in a similar way to the existing Local Mean and Local Median filters It sets the value of the target data point to the maximum value found in the window Automatic gain control and contrast normalisation The automatic gain control AGC and contrast normalisation filters uses an averaging process to reduce the amplitude variance of the data This can amplify smaller anomalies and dampen larger anomalies so that all anomalies appear more similar This is useful for enhancing smaller anomalies and reducing any tendency of larger anomalies to drown out the signal Automatic gain control filter for line data Line Filter only INTREPID processes each data point input value using the values in a surrounding window It divides the input value by the root mean square of the points in the window The AGC filter dialog box appears below Automatic Gain Control Filter Properties Automatic Gain Control Filter Properties Filter Name AGC Untitled Filter Space SPATIAL Filter Properties AGC 172 window size Accept Cancel Parameters AGC 1 2 Window size Number of data points in the AGC window The default value is 5 Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 15 Library Help Top 4 Back gt Contrast normalisation filter for grid data EE Library Help Top Spatial Convolution
19. f these are designed to emulate spectral domain filters See INTREPID spectral domain operations reference R14 for further information The predefined convolution kernels are all standard Earth Resource Mapping kernels For more information about these kernels refer to the ERMapper documentation Purpose Kernel type File names with extension ker Enhancing peaks and troughs Downward continuation down_cont_half down_cont_1 down_cont_2 Horizontal derivative hz10_2nd_ deriv hz13_2nd_ deriv hz1960_ 2nd deriv Second vertical derivative secondvertical Smoothing Averaging 3x3ave Low pass low_pass_4 Upward continuation up_cont_half up_cont_1 up_cont_2 Enhancing edges Horizontal edge enhance h_edge h_edge_5 Residual residual_1 residual _2 Sharp Edge sharpedge Extracting particular frequencies Band pass bandpass_3_5 High pass high_pass_4 Directional filter Sun filter East_West North_South Magnetic susceptibility Weiner wiener Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 8 Library Help Top lt 4 Back gt Structure of convolution kernel definition files The user defined convolution kernels are INTREPID auxiliary files each containing a Kernel Begin Kernel End block The files reside in the install_path kernel directory where install_path is the locat
20. in Decorrugation second low pass filter Secondary filter along correction m in Microlevelling The window size wavelength corresponds to the maximum width of anomalies to be processed by the Fuller filter i e identified as high frequency In the Decorrugation and Microlevelling tools this is measured in metres In the other tools it is measured as the number of data points The window size also corresponds to the number of coefficients used in the Fuller convolution process one per data point or grid cell in the window Normalise filter weights The Fuller filter is a convolution filter with a set of coefficients You can ensure that the filter does not cause an overall change in the mean of the data by normalising the filter weights making the coefficients add up to 1 1 D C Fraser B D Fuller and S H Ward Some Numerical Techniques for Application in Mining Exploration Geophysics vol XXXI NO 6 December 1966 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 10 Library Help Top Naudy filter Library Help Top lt 4 Back gt Fuller filter high low output options fixed in Profile Editor high pass Levelling low pass Decorrugation high pass then low pass Microlevelling low pass You can specify whether a Fuller filter will output the data identified as high frequency High Pass or output th
21. ion Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 12 Library Help Top lt 4 Back gt Output residuals This option reverses the action of the High Pass Low Pass Notch options above If you turn it on INTREPID will reject the data that it would normally pass and pass the data it would normally reject according to these options Replace trend in output fixed in Profile Editor Levelling Decorrugation Microlevelling all turned on Before applying the Naudy filter INTREPID removes first order trends overall slope in the data If this check box is on this is the default condition INTREPID will restore this trend after the filter process 4th Difference noise detection Profile Editor and Spreadsheet editor only This filter calculates the 4th difference of the Signal data Non zero 4th difference results indicate sudden changes in the data See the description of the diffn function in Section INTREPID Functions in INTREPID expressions and functions R12 for information about the 4th difference calculation dif 4 Gradient filter Profile Editor only The gradient filter calculates the slope of the Signal field with respect to time fiducial This is a useful indicator of rapid change and therefore a method of identifying noise Library Help Top 2012 Intrepid Geophysics lt 4 Back gt
22. ion of your INTREPID installation and have extension ker The kernel definition file contains definitions of seven parameters Earth Resource Mapping developed this format as an open standard INTREPID does not use some of the parameters in the format but requires them to be present in order for the definition to conform to the standard Name contains the name of the filter enclosed in double quotes Description contains the description of the kernel If the text of the description contains spaces it must be enclosed in double quotes Type Convolution required by the ERMapper standard Rows Columns The kernel consists of a matrix of coefficients These parameters specify the number of rows and columns of coefficients in the kernel If you specify a user defined kernel INTREPID displays the dimensions in the Status area of the display There must be an odd number of rows and of columns so that the kernel can be symmetrical around the target cell OkOnSubsampledData FALSE This statement is required by the ERMapper standard Array contains the matrix of coefficients For ease of reading Enclose the matrix in braces Place each row of the matrix in a separate line of the file e Place the opening on the same line as the words Array Place the alone on a line under the matrix Separate the coefficients within the rows by spaces Scalefactor 1 required by the ERMapper standard and currently not used by INTREPI
23. ional trends when you use a value closer to 1 Setting the value to 0 preserves the regional component MaxGain The maximum gain is an amplification limit for data output by the filter A cell may not deviate more than the value of this parameter from the mean of the cells in the window 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 16 Library Help Top lt 4 Back gt Hilbert transform Gridding Line Filter only The Hilbert Transform filter uses a finite difference operator to calculate an imaginary component of the input Quadrature It uses this as the filter result or combines it with the existing real component to give the Instantaneous Phase or Instantaneous Frequency The standard Hilbert transform dialog box appears below Hilbert Transform Filter Properties Hilbert Filter Properties Filter Name Filter Space HILBERT Filter Properties SSCS Filter Window Length ExtendDataUsng SSOS lt CS st S S S C Zero Pad C Mirror Pad Data Flipped Mirror Pad Data Output Options Hilbert C Complex Amplitude C Instantaneous Phase Phase Unwinding Options C Instantaneous Phase unwound C Instantaneous Frequency Phase Unwinding Threshold OK Cancel Parameters Filter Properties Filter Window Length The number of data points used by the Hilbert Transform finite difference operator The default v
24. is a Y reflection then an X reflection of the profile of the Signal values of the same number of original data points at that end of the line This is the default option for spatial domain filters Filter definition a vs kernel xer files Filter definition d files Using the Line Filter tool you can save and load filter definition files which specify the type and parameters for a filter These files have the extension fdf and reside in the install_path filters directory where instal1_path is the location of your INTREPID installation Filter definition files can specify spatial or spectral domain filters The name of the filter definition file will show in the Name text box of the filter properties dialog box See Loading and saving filter definitions in Line Filtering T31 for details User defined convolution kernel ker files Library Help Top You can specify a convolution filter using a set of coefficients for multiplying neighbouring data points or grid cells combining the results and calculating a new value for the target point or cell INTREPID stores the coefficients in a user defined convolution kernel file with the extension ker residing in the install_path kernels directory where install_path is the location of your INTREPID installation See User defined convolution kernelsfor details 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters
25. nding Threshold 299 OK Cancel INTREPID calculates initial Signal values for the data points in the extended region These can be based on nearby original data values See Extended region size and Data extension method for information Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 5 Library Help Top 4 Back gt Extended region size Hilbert transformation only INTREPID automatically calculates the length of the extended region for the Hilbert transform using the formula v1 2 p where p length data points of extended region w filter window length INTREPID automatically calculates a suitable extended region size for the other filters Data extension method Fuller filter Hilbert transformation Phillips automatic depth estimation only INTREPID has three options for extended region values as described below In the dialog box for the filter select the Data Extension Method option as required Zero Pad INTREPID sets all extended region values to zero Mirror Pad Data INTREPID extrapolates values so that the profile of the extended region Signal values is a Y reflection of the profile of the Signal values of the same number of original data points at that end of the line Flipped Mirror Pad Data INTREPID extrapolates values so that the profile of the extended region Signal values
26. total of 222 sec or 3 7 minutes If you don t wish to introduce any phase lag into your data design the filter accordingly Example 2 Lacoste 6 stage RC 106 second noise filter This filter does 3 stages of 1 way backwards then 1 stage of 1 way forward filtering then 1 stage of 2 way filtering 10 10 10 30 23 23 eg 10 sec back 10 sec back 10 sec back 30 sec forward 23 sec back 23 sec forward 2012 Intrepid Geophysics lt 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 21 Library Help Top lt 4 Back gt Gravity Inversion Line Filter only This is an implementation of the paper by Murthy amp Rao from Computers amp Geosciences Vol 15 No 7 pp1149 1156 A profile of gravity data is inverted to yield either Depths to the top of the basement surface below each point of gravity anomalies Anomaly of structure Parameter input Z Depth above which the structure or density Surface is to be calculated km De Density contrast gm cc default is 400 Optional Parameters to aid convergence Ztlt Minimum depth to interface km default is 1000 m Zblt Maximum depth to interface km default is 4000 m Parameter output Either Zt Depth to interface in km OR Gcal Anomaly of structure calculated in mgals 2012 Intrepid Geophysics lt 4 Back gt Library Help Top INTREPID User Manual INTREPID spatial and time dom
27. y noisy data Filter Space SPATIAL Fiducial Filter Properties Multiple forward and backwards RC filtering This option assumes no prior hardware RC lags where RC stands for Resistive C apacitive J Allow for LR hardware timing lags Set to airborne default times RC Times in seconds 0 5000 0 5000 0 5000 0 5000 0 5000 0 5000 0 5000 2 0 2 0 Extend D ata U sing C Zero Pad Mirror Pad Data C Flipped Mirror Pad Data Pad size in extra readings J Output Residuals OK Cancel If you select the curvature version INTREPID displays a further dialog box LaCoste Filter Parameters Fid Factor seconds __0 14 passes smoothing uns 4 Ok Cancer Library Help Top 2012 Intrepid Geophysics 4 Back gt INTREPID User Manual INTREPID spatial and time domain filters and transformations R13 20 Library Help Top Library Help Top lt 4 Back gt Parameters Filter Stages Number of stages in the filter RC Times in seconds Time in seconds for each filter stage Example 1 Lacoste 9 stage RC noise filter This filter does 3 stages of 1 way backwards then 3 stages of 2 way filtering 20 0 20 0 20 0 27 0 27 0 27 0 27 0 27 0 27 0 eg 20 sec back 20 sec back 20 sec back 27 sec forward 27 sec back x 3 To calculate the length of the filter add the numbers up they are in seconds so 20 20 20 60 sec one minute and 6 27 162 sec about 2 7 minute making a
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