NAME

     gradfilt - Apply a gradient filter to a velocity dataset.

SYNOPSIS

     gradfilt [-N ntap] [-O otap] [-rs rs] [-re re] [-ns ns] [-ne
     ne]  [-s  s]  [-e  e]  [-gmaxg gmaxg] [-gming gming] [-lmaxg
     lmaxg] [-lming lming] [-lth lth] [-hth hth] [-dz dz]  [-mask
     mask] [-V] [-?]  [-h]

DESCRIPTION

     gradfilt applies a gradient filter to a velocity dataset

     The filter rule is: Velocity variation from sample to sample
     must  fall within a user specified gradient range. Filtering
     is not performed if the velocity  is  within  the  specified
     range.  Globally,  the  same  filter  test is performed, but
     overall gradient from top (or mudline) to current  depth  is
     checked  to  see if it falls within the specified range. The
     global filter testing is referenced to the depth where velo-
     city first exceeds the low velocity threshold. Currently, if
     the velocity exceeds the  high  threshold,  nothing  special
     happens. You can write either the filtered velocity data, or
     a filter mask (with the -mask option). The mask is simply  a
     dataset with a sample value :
          0 if no filtering was performed
          1 if local filtering was performed
          2 if global filtering was performed
          3 if local and global filtering were performed

  Command line arguments
     -Nntap
          Enter the name of the input dataset.

     -Ootap
          Enter the name of the output dataset.

     -nsns
          Enter the trace number of the first  trace  to  process
          after  typing  -ns.   The  default  is to use the first
          trace of the record.

     -nene
          Enter the trace number of the  last  trace  to  process
          after typing -ne.  The default is to use the last trace
          of the record.

     -rsirs
          Enter the record number of the first record to  process
          after  typing  -rs.   The  default  is to use the first
          record of the dataset.


     -reire
          Enter the record number of the last record  to  process
          after  typing  -re.   The  default  is  to use the last
          record of the dataset.

     -s s Enter the start time (default first samp).

     -e e Enter the end time (default last sample).

     -lth lth
          Enter the low velocity threshold (default 0).

     -hth hth
          Enter the high velocity threshold (default 99999).

     -dz dz
          Enter the depth sampling interval.

     -mask mask
          Use this option to output the mask, not the 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 this.

     -h   Enter this option to get online help.  The program will
          terminate after printing this.

SEE ALSO

     pptrnehz, ppetn, ppg2psi, psi2ppg, ppfilt,  psifilt3,  ptop,
     fillhdr, gradfilt, mshowray

BUGS

     None known.

AUTHORS

     N. D. Whitmore, Jr., Mary Ann Thornton, Martin L. Albertin.

COPYRIGHT

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