NAME

     velnotch - apply deghosting operation to seismic traces

SYNOPSIS

     velnotch [ -Nntap ] [ -Ootap ] [ -rsirs ] [ -reire ] [ -vvel
     ] [ -dxdx ] [ -tpct ] [ -wthr ] [ -pipow ] [ -V ] [ -? ]

DESCRIPTION

     velnotch computes an f-k notch in f-k space and applies as a
     multiplicative  mask to the f-k transformed data.  The notch
     will work in both dip quadrants (in fact you  can't  prevent
     it).

     velnotch 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)

     -hh  Enter the source or receiver depth in ft or m  (default
          = none)

     -vvel
          Enter the water velocity (ft,m/s) ( default = none)

     -tpct
          Enter the % taper in time and space (default  =  2.5%).
          In frequency and wavenumber, the taper is also applied:
          in frequency it covers the low end as well as the  high
          end,  i.e.  pct on each side.  Hence a pct taper cannot
          be greater than 50%.  In wavenumber the taper just cov-
          ers  the  highs  with  a notch at the water velocity to
          prevent artifacts having the water speed.

     -wthr
          Enter the % notch threshold.   This  defines  the  1/2-
          width of the notch in terms of a % of the center value.
          Default is 10%, i.e. the low end is .9 times center  k-
          value, and the high end is 1.1 times the center value.

     -pipow
          Enter the power exponent  of  the  notch  reject.   The
          notch  reject  factor  is computed as a ratio of the k-
          distance to the center notch value of  k  to  the  1/2-
          width  of the notch (as measured by the low & high ends
          above).  This ration is then powered by  the  exponent.
          Default = 4

     -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

AUTHOR

     Paul Gutowski, APR x3146

COPYRIGHT

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