NAME

     rstak  - vertically stack groups of records

SYNOPSIS

     rstak [ -Nntap ] [ -Ootap ] [ -nnstk ] [ -B ] [ -S ] [ -3d ]
     [ -xffar ] [ -xddx ] [ -V ] [ -? ]

DESCRIPTION

     rstak takes groups on records from a data set and vertically
     stacks  them either trace by trace (i.e. keys on trace posi-
     tion regardless of trace offset) or  into  bins  defined  by
     input  spread  geometetry.   For the nonbinned mode the dis-
     tances and static values for the output traces are  averaged
     over  all  live  values  in  the stacking groups.  The other
     trace header values are defined by the first  nonzero  input
     record.

     For the default unbinned option it's a good idea to have the
     input records arranged in such a way that within each record
     traces are positioned according to their offset,  e.g.  run-
     ning  a  disort.   This  may not be a problem for input shot
     data particularly in the marine case  but  the  user  should
     check  to  make  sure  of the offset distribution with trace
     number.

     For land data it's a good idea  also  to  have  statics  (at
     least  first  break  statics) run on the data before running
     this program.  Otherwise large static differences will  cer-
     tainly result in rubbish.

     rstak gets both its data and  its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the number of groups to stack, the  option  the  stack  into
     binned distances, and verbose printout, if desired.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing -N.  This may be an input pipe.  This input file
          should include the  complete  path  name  if  the  file
          resides in a different directory. Example -N1/vsp/dummy
          tells the program to look for file 'dummy' in directory
          '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).

     -n nstk
          Enter the number of records to stack in each group  (no
          default).   If  this  is not an integral divisor of the
          input number of records then a partial group of records
          at the end of the data set will be stacked.

     -B   Enter the command line argument '-B' to stack based  on
          distance bins (see parameters below).

     -S   Enter the command line argument '-S' for bin option  if
          spread is split.

     -3d  Enter the command line argument '-3d' to tell the  pro-
          gram  the  input  is  3D CDP data.  This allows reading
          more info from the line header,  i.e.  MnLnIn,  MxLnIn,
          MnDpIn, MxDpIn, CDPFld.

     -xf far
          Enter the far  (maximum)  offset  (ft,m).   For  single
          ender  with negative trace distances this will be nega-
          tive; for positive trace distances this will  be  posi-
          tive.  For split spreads this value will be negative.

     -xd dx
          Enter the bin  (group)  size  (ft,m).   Note:  the  bin
          option  could  easily  result  in a different number of
          traces per record on output.   In  fact  this  will  be
          equal  to  the  number of bins determined by the spread
          geometry.

     -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.