NAME

     dmofast  - do log-stretch dmo on nmo corrected common offset
     data

SYNOPSIS

     dmofast [ -Nntap ] [ -Ootap ] [ -sist ] [ -eiend ] [ -nsnstr
     ]  [ -nenetr ] [ -rsnrst ] [ -renred ] [ -fsfs ] [ -dxdx ] [
     -R ] [ -V ] [ -? ]

DESCRIPTION

     dmofast is a dmo implementation from  the  Center  for  Wave
     Phenomena at CSM.  It is an exact dmo algorithm based on 2-d
     fft's of log-stretched data.  Thus the  common  offset  data
     must  be  passed  through  program  stretch  before (forward
     stretch) and after (reverse stretch or  squeeze)  dmo.   The
     stretch/squeeze  operation is very fast so very little over-
     head is incurred.  The result is a dmo algorithm  that  runs
     about 10 times faster than others of the breed.

     The nmo corrections are most conveniently done on CDP sorted
     data  after  which  the data are re-sorted (by first ruuning
     presort on the CDP data and then running sisort ... -X) into
     the  common  offset domain.  The output of dmofast is in the
     common offset domain and therefore must be sorted back  into
     the  primary domain of interest.  This means another presort
     must be run to build the mapping from offsets to  the  other
     domains.

     You should probably post filter the results with a  generous
     pass band (e.g. 5 - 100)

     dmofast gets both its data and its parameters  from  command
     line  arguments.  These arguments specify the input, output,
     trace spacing, the start and end traces, and  verbose  prin-
     tout, if desired.  The dmo operation may be reversed.

  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.  The input data  must  be
          NMO-corrected.  This input file should include the com-
          plete 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).

     -s ist
          Enter the start time (samples) of the data window.  The
          default  is  the  beginning  of the trace.  Effectively
          this entry and the one below window off  a  portion  of
          the data in time.

     -e iend
          Enter the end time (samples) of the data  window.   The
          default is the end of the trace.

     -ns nstr
          Enter the start trace number.  The default is the first
          trace of the record.

     -ne netr
          Enter the end trace number. The  default  is  the  last
          trace of the record.

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

     -re nred
          Enter end record number.  Default value is last record.

     -dx dx
          Enter the input trace spacing of the offsets in ft or m
          (no default).

     -fs fs
          Enter the temporal scaling factor, i.e. the  factor  by
          which  the  sample  interval  is  multiplied.  This can
          often greatly reduce run time and  memory  requirements
          for  the  program  at little or no detriment to the dmo
          operation. Default = 1, i.e. no  scaling.   The  factor
          must be integer and > 1

     -R   Enter the command line argument '-R' to do the  inverse
          dmo operation.

     -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.

BUGS

     must have as input data output  from  program  stretch,  and
     must  have  its  output  processed  by  the reverse stretch.
     Example:

          stretch -Ninput | dmofast -dx25 | stretch -Ooutdata -R

SEE ALSO

     stretch, dmo

AUTHOR

     Chris Liner, formerly Colorado School of Mines.   Reference:
     GEOPHYS, v35, pp595-607, 1990

COPYRIGHT

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