NAME
fkshape - module to apply user defined radial spatial fre-
quency shaping filter to 2D FFT dataset.
SYNOPSIS
fkshape [ -Nntap ] [ -Ootap ] [ -Potap ] [ -rsnrst ] [
-renred ] [ -sst ] [ -eed ] [ -dxDX ] [ -dyDY ] [ -nbinsnum
] [ -expe ] [ -b1b1 ] [ -b2b2 ] [ -b3b3 ] [ -b4b4 ] [ -diff
] [ -V ] [ -? -h -help ]
DESCRIPTION
fkshape applies a user defined radial spatial frequency
filter to an input 2D FFT dataset of the type created by the
USP routine fftxy . The filter is supplied either as an
XSD format pick file or described on the command line. The
presence of a pick file overrides any command line defini-
tion. Each segment in the pick file will be treated as an
induvidual filter so that if there are N records in the
input dataset and M segments in the pick file, the output
dataset with contain N x M records. Each input record
will be filtered by all filters described in the pick file.
The filter design may be picked from an xsd display of the
output from the USP program fkrad which produces a
radial power spectrum of the input 2D FFT record [see man
page]. If no pick file is attached the user may specify a
set of bin co-ordinates delineating a trapezoidal filter -
b1 -b2 -b3 -b4 . The number of bins into which to divide
the spatial frequencies may be defined using -nbins or by
letting the program default. In the case of a default the
routine will construct the same number of bins as con-
structed for the display created by the routine fkrad . An
exponent may be defined using -exp which will be used to
power the radial spectrum. Any combination of the above
parameters may be entered. To perform a Low Cut operation
simply define -b1 and -b2 only. The routine will default
to passing the rest of the spectra out to the radial spatial
Nyquist. To perform a High Cut operation simply define
-b3 and -b4 only. The routine will default to passing the
spectra from zero out to the radial cutoffs specified.
There is a huge difference between the filters applied using
the pick file and command line options. The pick file
option utilizes a shaping filter appropriate for potential
fields data application. It was designed to allow
regional/residual separation using picks made on radial
power spectra. The command line definition option is the
old trapezoidal pass/reject option familiar to most seismol-
ogists.
fkshape gets both its data and its parameters from command
line arguments. These arguments specify the input, output
datasets, the input pick file, the start and end records to
pass, the start and end records to filter, the X and Y sam-
ple intervals, the number of bins into which to group the
radial frequencies, the filter bin trapezoidal definition,
the type of output desired (filtered data or difference),
and verbose printout, if desired.
Command line arguments
-N ntap
Enter the input data set name or file immediately after
typing -N unless the input is from a pipe in which case
the -N entry must be omitted. This input file should
include the complete path name if the file resides in a
different directory. Example -N/b/vsp/dummy tells the
program to look for file 'dummy' in directory '/b/vsp'.
-O otap
Enter the output data set name or file immediately
after typing -O. This output file is not required when
piping the output to another process. The output data
set also requires the full path name (see above).
-P ptap
Enter the input xsd pick file name. Default is to get
filtering parameters from command line.
-rs nrst
Enter start record number to pass. Default value is
the first record.
-re nred
Enter end record number to pass. Default value is last
record.
-s st
Enter start record number to filter. Default value is
the first record.
-e ed
Enter end record number to filter. Default value is
last record.
-dx DX
Enter the sample interval in the X [trace-wise] direc-
tion.
-dy DY
Enter the sample interval in the Y [sample-wise] direc-
tion.
-nbins num
Enter the number of bins into which to group the radial
spatial frequencies for filtering. The default is to
let the program determine this number. It will end up
being the larger of the number of samples from the ori-
gin to Nyquist in the X or Y orientation of the input
2D fft. If a pick file is attached the number of bins
will be taken from the number of traces found in the
pickfile header. This would correspond to the number
of traces in the fkrad display from which the picks
were derived.
-exp n
Enter the powering exponent to use if no XSD pickfile
is attached. This will be applied as a function of
radial frequency. Default is 0.0 [i.e not used].
-b1 b1
Enter the low cut-off radial frequency for the command
line filter definition option. This is not used when a
XSD pickfile is attached. The amplitude at Radial
frequencies at or below this bin number will be set to
zero. Default is 1.
-b2 b2
Enter the lower 100 % pass point for the trapzoidal
filter. The amplitude at Radial frequencies at or
above this bin number up to and including the bin
described by -b3 below will be passed unchanged
[unless of course you have entered a value for -exp
above]. Default is 0.
-b3 b3
Enter the upper 100 % pass point for the trapzoidal
filter. The amplitude at Radial frequencies at or
below this bin number down to and including the bin
described by -b2 above will be passed unchanged
[unless of course you have entered a value for -exp
above]. Default is 0.
-b4 b4
Enter the upper cut-off radial frequency for the com-
mand line filter definition option. Amplitudes at
radial frequencies above this bin number will be set to
zero. Default is 0.
-diff
Enter the command line argument -diff to request that
the output from the routine be the result of the input
- the filtered input. The default is to output the
filtered input only.
-V Enter the command line argument '-V' to get additional
printout.
-? -h -help
Enter the command line argument '-?' or -h or -
help to get online help. The program terminates after
the help screen is printed.
BUGS
Unknown
SEE ALSO
fkrad(1) fftxy(1)
AUTHOR
Paul G. A. Garossino, Mar/94,
[APR:3932:zpgg07@trc.amoco.com]
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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