NAME

     presortc  - compute sort tables (elastic processing)

SYNOPSIS

     presortc [ -Nntap ] [ -Ootap ] [ -Hw1TrWrd1 ] [ -Hw2TrWrd2 ]
     [  -Hw3TrWrd3 ] [ -Hw4TrWrd4 ] [ -HwrTrWrdr ] [ -HwsTrWrds ]
     [ -M ] [ -offoff ] [ -grpgrp ] [ -R ] [ -X ] [ -S ] [ -K ] [
     -V ] [ -? ]

DESCRIPTION

     presortc computes the common source, common receiver, common
     depth,  and  common offset sort table, or alternately, three
     arbitrary primary sorts from  user  specified  trace  header
     words  plus one secondary sort.  The header words are speci-
     fied by mnemonic (see scan documentation for list of  header
     mnemonics  and  their  descriptions).   For further notes on
     sorting see the man page for presort.

     The sort table has the following entries:

     LINE 1 - -1 (flag)

     LINE 2 - total number traces to be sorted

     LINE 3 - receiver/source components  actually  present  (the
     code  for  each  trace  is  a  2  digit number, the first is
     receiver, the second is source; the numbers: 3 = vertical, 1
     = crossline, 2 = inline).

     LINE 4 - four pairs (number gathers,  number  traces/gather)
     for  common receiver, co mmon shot, common depth, and common
     offset

     LINE 5 - first receiver index, receiver index increment

     LINE 6,7,... first 3 numbers are the sorted primary  indices
     (receiver,  shot,  depth  ); the next 3 pairs of numbers are
     the corresponding sequential record and trace l ocations for
     the primary indices; the next number is the offset; the next
     pair is the record and trace location of the  common  offset
     sorted index found in the last sort table location.

     presortc gets both its data and its parameters from  command
     line  arguments.  These arguments specify the input, output,
     and verbos printout, if desired.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing -N.  This 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 'vsp' stored on the 'b' disk.

     -O otap
          Enter the output data set name or file (i.e. sort table
          name) immediately after typing -O.  The output data set
          also requires the full path name (see above).

     -hw1 TrWrd1
          Enter the first trace header word mnemonic to  sort  on
          (one of three).  Default = RecInd (receiver index).

     -hw2 TrWrd2
          Enter the second trace header word mnemonic to sort  on
          (two of three).  Default = SrcLoc (source index (source
          point x10)).

     -hw3 TrWrd3
          Enter the third trace header word mnemonic to  sort  on
          (three of three).  Default = DphInd (depth index).

     -hw4 TrWrd4
          Enter the secondary trace header word mnemonic to  sort
          on.  Default = DstSgn (signed trace distance).

     -hwr TrWrdr
          Enter  the  receiver  component   trace   header   word
          mnemonic.  Default = ToStUn

     -hws TrWrds
          Enter the source component trace header word  mnemonic.
          Default = ToTmAU

     -M   Enter the command line argument '-M' to sort on  binned
          trace distances.  These are
           derived from the command line arguments below.   Note:
          this will not change the
           actual trace distances on disk

     -off off
          Enter the absolute maximum offset  found  in  the  data
          (ft,m).   If  this is not known try running scan with a
          -S (for summary) on the command line.  This wi ll  tell
          you the max & min offsets for each record.

     -grp grp
          Enter the group interval (ft,m).  This is used with the
          offset  above to derive a m odel spread for binning the
          distances.

     -R   Enter the command line argument '-R' to round the trace
          distances  to the nearest 10 units (ft, m) before sort-
          ing

     -X   Enter the command line argument '-X' to to retain  ori-
          ginal  record  numbers  in the sort table.  This option
          should be used only if one wishes to eyeball  the  sort
          table to see where the traces will go upon execution of
          comport and is not intended for normal processing

     -K   Enter the command line argument  '-K'  to  retain  dead
          traces in the sort table.  This takes up more space but
          the table is now an exact roadmap of the data on  disk.
          NOTE:   with  this option the dead traces must have all
          the correct header indices.  If they do not you are  in
          big trouble.

     -S   Enter the command line  argument  '-S'  to  divide  the
          source point numbers (which are multiplied by 10 in the
          traces headers) by 10.   If  the  actual  source  point
          numbers on the ground are fractional dividing by 10 and
          converting to an integer will cause the  appearance  of
          groups of identical soc point numbers.

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

     -?

SEE ALSO

     presort for more explanation of the sort table

COPYRIGHT

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