NAME

     mapextract - map the first occurence  of  a  value  in  each
     trace of a data volume.

SYNTAX

     mapextract [ -N filename -O filename
                  -val value -z0 z_origin -dz delta_z
                  -dir direction -emask emask -h -V ]

DESCRIPTION

     mapextract  creates  a  USP  format  map  that  records  the
     occurence  (depth  or  time) of a user-defined "property" in
     each trace of an input volume. The resulting map  will  con-
     sist of NumRec(input) traces of NumTrc(input) samples.

     When the  search  for  the  specified  function  fails,  the
     resulting  map  will  contain  the value of an embedded mask
     (-emask).

     User overrides -z0 and -dz (for the z origin  and  delta  z)
     allow  the  user  to  scale  and  shift the mapped depths as
     desired.

     In the initial  release,  the  user-defined  properties  are
     either  the  first  or last occurence of a specific value in
     each trace. The last occurence is detected by  changing  the
     direction  of  analysis along the trace with parameter -dir.
     Other properties can be easily implemented as needed.

OPTIONS

     -N filename [default: stdin]
          Enter the name of the input file immediately after typ-
          ing  -N.   This  file  should include the relative path
          name if the file resides in a different directory.

     -O filename [default: stdout]
          Enter the output dataset name or file immediately after
          typing  -O.  This file should include the relative path
          name if the file resides in a different directory.

     -val value [default: none]
          Enter the value to search for. The depth of  the  first
          occurence  of this value will be recorded in the output
          map.

     -z0 z_origin [default: z_origin=0.0]
          Enter the origin of the z  axis  used  to  compute  the
          depth at which the "property" is detected.

     -dz delta_z [default: delta_z=1e-3*Dz1000]
          Enter the z axis sample interval used  to  compute  the
          depth at which the "property" is detected.

          In the result,   Depth = z0 + dz*(Sample No. - 1)


     -dir direction [default: direction=fwd]
          Enter the direction  the  search  proceeds  along  each
          trace. When direction=fwd, the trace samples are inter-
          rogated from 1 to NumSmp by 1. When direction=rev,  the
          trace samples are interrogated from NumSmp to 1 by -1.

     -emask emask [default: emask=-1e+37]
          Enter the value of map samples when the  search  fails,
          resulting in an undefined surface.

     -V   Print verbose information during processing.

     -h or -?
          Print online help to the terminal.

EXAMPLES

         mapextract -N vel_in.usp -O tos_map.usp -val 4478 \
                    -z0 0.0 -dz 12.5 -emask -99999

     This will create a map recording  the  depth  to  the  first
     occurence  of  4478.0  in  each trace of the input file. The
     resulting map will contain the embedded mask -99999.0  when-
     ever  4478  is  not on a trace. Sample interval and z origin
     overrides are used to control depth scaling and bias.

         mapextract -N vel_in.usp -O bos_map.usp \
                    -val 4478 -dir rev -emask -99999

     This will create a map  recording  the  depth  to  the  last
     occurence  of  4478.0  in  each trace of the input file. The
     resulting map will contain the embedded mask -99999.0  when-
     ever 4478 is not on a trace.

BUGS

     None known

AUTHORS

     M.J. O'Brien - Allied Geophysics Inc.

COPYRIGHTS

     Copyright  2001,  Allied  Geophysics,   Inc.    All   Rights
     Reserved.

     Portions of this application are also protected as follows:

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