NAME

     s2dsp  - module to compute 2-d (f-k) amplitude spectra

SYNOPSIS

     samps [ -Nntap ] [ -Ootap ] [ -rsirs ] [ -reire ] [ -tsits ]
     [ -teite ] [ -siwst ] [ -eiwed ] [ -moismo ] [ -ggi ] [ -S ]
     [ -D ] [ -V ] [ -? ]

DESCRIPTION

     s2dsp computes a 2-d amplitude spectrum for the  input  data
     as  per  the  input parameters. The FFT Fourier transform is
     used for reasons of speed; hence  both  window  lengths  and
     number  of  traces  are  buffered to the nearest power of 2.
     The output data consist of amplitude  spectra  that  are  in
     normal  usp  format  and  can be plotted by means of vaplot,
     contour, or other sis plotting programs.  The sample  inter-
     val  in  the  output data line header is set to milli-Hz and
     hence output scales can be read as Hertz.  A  typical  plot-
     ting  "time"  scale  might  be  .04  in/"sec" thus giving 25
     Hz/in.  Note that number of output traces will be a power of
     2 .ge. number input traces +1.  (This places spatial Nyquist
     on both sides of spectrum.)  The output trace  headers  have
     little  meaning  other than the trace count cell (record no.
     is 1).


     s2dsp gets both its data and  its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the start and end records and traces, start  and  end  times
     for  windows,  smoothing, scaling options, and verbose prin-
     tout, if desired.  Constraints:  number of traces .le.  256,
     length  of window .le. 2048 samples.  The input trace set is
     bracketed by starting record/trace and ending  record/trace,
     inclusively.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing  -N.  If piping in, this command line entry will
          be omitted.  The 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).

     -rs irs
          Enter the start record number.  Default  value  is  the
          first record.

     -re ire
          Enter the end record number.   Default  value  is  last
          record.

     -ts its
          Enter start trace number.  Default is  first  trace  of
          record.

     -te ite
          Enter end trace number.  Default value is last trace of
          record.   End record/trace subject to internal reset if
          total no. of traces .gt. 256.

     -s iwst
          Enter start time of window for  2-d  spectrum  computa-
          tion.  Default is the start of the trace.

     -e iwed
          Enter end of window for harmonic analysis.  Default  is
          end  of  trace.   Subject to internal reset if analysis
          window .gt. 2048 samples.

     -mo ismo
          Enter smoothing strength, e.g. 5.  Default is none.

     -g gi
          Enter group interval for stacked data.  Program  places
          this in line header to define spatial increment.  Could
          be used  by  subsequent  plotting  program.   Otherwise
          ignored.  Default is 0 which maintains input data group
          interval.

     -S   Enter the command line argument '-S' to scale  spectrum
          to max value of unity.

     -D   Enter the command line argument '-D' to  convert  spec-
          trum  to  dB.   ('-D' also scales spectrum to max value
          unity before taking logarithm).

     -V   Enter the command line argument '-V' to get  additional
          printout.

     -?   Enter the command line  argument  '-?'  to  get  online
          help.   The program terminates after the help screen is
          printed.

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.