NAME

     vsm3d - 3D velocity smoother

SYNTAX

     vsm3d [ -N filename -O filename
             -1sm n1sm -2sm n2sm  -3sm n3sm -ns niter
             -emask emask -I -V -h ]

DESCRIPTION

     vsm3d performs iterative smoothing of a USP file.  Data  can
     be  inverted  prior to (and subsequently after) smoothing at
     the user's request. The smoother is  a  simple  boxcar  with
     variable  lengths on each of three axes. Using more than one
     iteration effectively changes the  shape  and  size  of  the
     smoothing  operator.  vsm3d  can  also  be  made aware of an
     embedded mask and will not use masked samples in the smooth-
     ing operation.

     vsm3d loads the entire input volume into memory and proceeds
     to  create  a  second, memory resident, smoothed volume. For
     this reason, large volumes on machines with limitted memory,
     may  need  to  be  split  into  pieces for smoothing and the
     results spliced back together. When doing  this,  subvolumes
     should  account  for  operator overlap to avoid seems in the
     result.

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.


     -1sm n1sm [default: n1sm=7]
          Enter the size of the smoother along axis 1 (the sample
          axis).

     -2sm n2sm [default: n2sm=21]
          Enter the size of the smoother along axis 2 (the  trace
          axis).

     -3sm n1sm [default: n3sm=21]
          Enter the size of the smoother along axis 3 (the record
          axis).

     In vsm3d, sizes are given in number of samples.
     -ns niter [default: niter=1]
          Enter the number of smoothing iterations to perform.

     -I [default: .FALSE.]
          Use -I on the command line to invert (reciprocate) sam-
          ples before (and after) smoothing.

     -emask emask [default: none]
          Enter the value to use for an embedded mask. These sam-
          ples  are passed unchanged and are not used in operator
          computation. An example appliction is  if  you  have  a
          constant  velocity  anomaly  in an arbitrary background
          field and you want to smooth only the background.  Then
          you  would  set  the  embedded mask to the value of the
          anomaly with -emask anomaly.  Leaving  -emask  off  the
          command line turns the masking function off.

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

EXAMPLES

         vsm3d -Nvel_in.usp -Ovel_sm.usp -I

     This will translate velocity  to  slowness,  smooth  with  a
     default  7x21x21  point boxcar operator, and transform slow-
     ness back to velocity.

         vsm3d -Nmap_in.usp -Omap_sm.usp \
               -1sm 5 -2sm 5 -ns 2 -emask -99999

     This will smooth a USP format map in 2 iterations with a 5x5
     smoother.  Values  where the surface is not defined (-99999)
     are not smoothed and are not  included  when  computing  the
     smoothing operator.

BUGS

     None known

AUTHORS

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

COPYRIGHTS

     Copyright  2002,  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.