NAME

     rstak3d  - vertically stack groups of 3D records  either  in
     in-line or cross-line direction

SYNOPSIS

     rstak3d [ -Nntap ] [ -Ootap ] [ -nnstk ] [ -S ]  [  -C  ]  [
     -xffar ] [ -xddx ] [ -V ] [ -? ]

DESCRIPTION

     rstak3d takes rolling groups of records from a 3D data  set,
     either  along  constant DI's or along constant LI's (in-line
     or cross-line), and vertically stacks them into bins defined
     by  input spread geometetry.  Output headers are a composite
     of the headers going into the rolling  stack,  i.e.  headers
     from  nondead contributions to the stack are placed into the
     output array.  Trace distances output corrspond to the model
     spread  geometry and bins that end up with no stacked traces
     are marked dead with a zero trace.   The  number  of  output
     traces  per  record  will  be  qeual  to  the number of bins
     defined by the spread geometry.

     The two modes are stack (1) common LI's and (2) common  DI's
     (respectively  generate  a  cross-line  stack  or an in-line
     stack).  For either mode the number of records  inserted  in
     the  line header will be the number of "rolls" of the verti-
     cal stack times the number of  LI's  or  DI's.   The  record
     number  appearing in the trace headers will only change with
     the "roll" of the stack, i.e. will be numbered 1 through the
     number of partial stacks.

     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.

     rstak3d gets both its data and its parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the number of groups to stack, whether the stack  is  to  be
     in-line or cross-line, 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 can be piped only if the in-line
          mode (default) is active; it must be a named disk  file
          if the -C (cross-line) mode is selected.

     -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.

     -C   Enter the command line argument  '-C'  to  stack  DI's,
          i.e.  the output will run along LI's (cross-line).  The
          default is to stack LI's.

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

     -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.

BUGS

     Currently the vertical stack  is  not  scaled  according  to
     either  the  number  of records going into to each "roll" or
     the number of live samples in each record.  The only scaling
     done  is if in a stack if more than 1 input trace falls into
     a bin an average trace is generated.

     Aside from the trace distances and the  LI  and  DI  numbers
     little  credence  should  be  placed  in  the trace headers.
     Later if this presents a problem we may have to do something
     cleverer  like compositing say the shot point numbers into a
     proper average, etc.

SEE ALSO

     sr3d1, sr3d2, or presort3d, sisort3d, pack3d

COPYRIGHT

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