NAME

     dipfk - fan filter (velocity driven)  output  of  fft2da  or
     fftxy

SYNOPSIS

     dipfk [ -Nntap ] [ -Ootap ] [ -rsirs ] [ -reire ] [  -vsvel1
     ] [ -vevel2 ] [ -dxdx ] [ -tpct ] [ -pipow ] [ -V ] [ -P ] [
     -? ]

DESCRIPTION

     dipfk computes an f-k fan (pass or reject) in f-k space  and
     applies  it  as a multiplicative mask to the f-k transformed
     data output by program fft2da.  The fan may be defined by  2
     velocities  (either  may be negative to get the opposite dip
     sense), or by a single velocity and a % deviation.

     dipfk will only work on the output of the f-k transform pro-
     gram  fft2da,  i.e.  the  user  will have to pipe operations
     together to build a true fan filter:

     [...] | fft2da [...] | dipfk [...] | fft2da -R | [...]

     dipfk gets both its data and  its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the trace spacing, the velocity to be nothced, the taper  %,
     and the notch power factor.

  Command line arguments
     -Nntap
          Enter the input data set name or file immediately after
          typing  -N;  entering  nothing  specifies a stdin pipe.
          This input put 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.

     -Ootap
          Enter the output data  set  name  or  file  immediately
          after typing -O.  This output file is not required when
          piping the output to another process.  The output  data
          set also requires the full path name (see above).

     -rs irs
          (integer)  First  record  to  process  (default  =  1).
          Records  less than this value will not be processed but
          will be passed.

     -re ire
          (integer) Last  record  to  process  (default  =  all).
          Records  greater  than this value will not be processed
          but will be passed.

     -dx dx
          Input trace spacing (ft,m) (default  =  none,  must  be
          entered)

     -vsvel1
          Enter the starting velocity of fan (ft,m/s).  Default =
          none

     -vevel2
          Enter the ending velocity of fan (ft,m/s).   Default  =
          none.  see alternative method of entering fan below

     -tpct
          Enter the % deviation either side of a single  velocity
          (either  vel1  or  vel2)  chosen above.  For example if
          vel1=3000 and pct=10, the upper  and  lower  velocities
          would  be  3300  and 2700.  If the fan should cross the
          zero velocity bounary (either negative or positive  dip
          sides) the fan will be truncated at the boundary with a
          small absolute velocity.

     -pipow
          Enter the power exponent of the  filter  edges.   Some-
          times  if  the fan is very narrow because of the radial
          smoothing done  the  reject  will  not  be  deep.   The
          exponent  powers the values of the filter with the hope
          that a small reject will get powered into a larger one.
          Default = 1

     -P   Enter the command line argument '-P' to pass within the
          fan rather than reject

     -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.

BUGS

     Currently this proogram will only work on output of  fft2da,
     the  f-k  transform  program  or fftxy, the Kx-Ky 2D spatial
     transform

SEE ALSO

     fft2da, polymute, fftxy

AUTHOR

     Paul Gutowski, APR x3146

COPYRIGHT

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