NAME

     datumt5 - Kirchhoff wavefield extrapolation (down or up)

SYNOPSIS

     datumt5 [ -Nntap ] [ -Ootap ] [ -Vtapvtap ]  [  -rsirs  ]  [
     -reire  ] [ -t0tzero ] [ -vmutevmute ] [ -fmaxfmax ] [ -nda-
     tumnzdatm ] [ -nraynray ] [ -slints ]  [  -taperitaper  ]  [
     -grpintgrpint  ] [ -dipmaxdipmax ] [ -dipfildipfil ] [ -ire-
     virev ] [ -jflagjflag  ]  [  -x0jxgrp0  ]  [  -sxnxave  ]  [
     -sznzave ] [ -V ] [ -S ] [ -P ] [ -? ]

DESCRIPTION

     datumt5 extrapolates seismic wavefields (up or down) through
     a  prescribed  velocity  model  to a new datum level using a
     Kirchhoff sumation approach.  The program  accomodates  both
     the  prestack  and  postack  cases.  In  the  prestack case,
     sources and receivers are  moved  to  the  new  datum  level
     seperately.  Thus,  to accomplish total redatuming of a sur-
     face seismic line requires two exections of the program in a
     cascaded fashion:

     Common Source Data --> Datum Receivers -->  Sort  to  Common
     Group --> Datum Receivers to New Level --> Continue Process-
     ing.

     Datumt5 gets data and parameters  from  command  line  argu-
     ments.  These  arguments  specify the input and output trace
     data,

  Command line arguments
     -Nntap
          Enter input data set name  or  file  immediately  after
          typing  -N;  entering  nothing  specifies a stdin pipe.
          This 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 subdirectory 'vsp' stored in directory b.

     -Ootap
          Enter output data set name or  file  immediately  after
          typing  -O.  This output file is not required when pip-
          ing the output to another process.  The output data set
          also requires the full path name (see above).

     -VtapVtap
          Enter the input velocity model data set  name.  Besides
          containing  the  veloicty  information, the appropriate
          cell dimensions and any arbitray datum  level  informa-
          tion  must be contained in the appropriate header posi-
          tions.


     -rs irs
          (integer)    Enter    first    record    to    process.
          (default = 1)

     -re ire
          (integer)    Enter    last    record    to     process.
          (default = all)

     -ns ns
          Enter first trace in record to process. (default = 1)

     -ne ne
          Enter last trace in record to process.  (default = all)

     -t0 tzero
          Enter mute start time (ms).  (default = 0)

     -vm vmute
          Enter mute velocity (ft or  m  per  sec).   (default  =
          99999.)

     -ndatum nzdatm
          Enter new datum depth (in cells) if datuming too a flat
          surface.  (default = 0.)

     -VAR nzdatm
          Enter '-VAR' if datuming datuming to/from an  arbitrary
          datum level (ie., not flat).

     -nray nray
          Enter the number of rays to shoot from each receiver or
          shot location  (default = 45; maximum = 180)

     -dipmax dipmax
          Enter the maximum ray emergence angle (default = 45)

     -dipfil dipfil
          Enter  the  minimum  number  of   sample   points   per
          wavelength. (default = 2)

     -grpint grpint
          Enter the group interval  (no default)

     -x0 jxgrp0
          Enter the group location (gi)  which  corresponds  with
          the left side of the velocity model.  (no default)

     -S   Enter '-S' to datum source locations.

     -sl ints
          If datuming sources, enter the number  of  group  loca-
          tions per source location (default = 1)

     -irev
          Enter '-irev' to datum upward (upward extrapolate).

     -sx nxave
          enter the number of cells to smooth the velocity  model
          in the x direction. (default = 1)

     -sz nzave
          enter the number of cells to smooth the velocity  model
          in the z direction. (default = 1)

     -POST
          Enter '-POST' to datum stacked or presumed zero  offset
          data.

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

     -?   Enter this (or '-?' if you are running in  c-shell)  to
          get  online  help.   The  program  will terminate after
          printing a list of parameters.

COPYRIGHT

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