NAME

     taper  - apply a simple but trace header word driven spatial
     taper to a seismic line.

SYNOPSIS

     taper [ -Nntap ] [ -Ootap ]  [  -htrhd_keyword  ]  [  -star-
     tupstartup ] [ -endupendup ] [ -startdownstartdown ] [ -end-
     downenddown ] [ -L ] [ -H ] [ -B ] [ -V ] [ -? ]

DESCRIPTION

     taper will apply a spatial taper (ramp) to  a  seismic  line
     according to the value of a user specified trace header word
     and command line arguments. Options include linear,  hamming
     and blackman tapers.

  Command line arguments
     -Nntap
          Enter the full path name of  the  file  containing  the
          data set.  If not specified, input is expected to be on
          standard input. The program will give an error  message
          if  the input file is read protected.  If no input file
          is given, and there is no standard input,  the  program
          will hang.  (default is standard input )

     -Ootap
          Enter the full path name for the output  file.  If  not
          specified,  standard  output is expected to be on stan-
          dard output. The program will give an error message  if
          the  output  file  is  being written to a write protect
          directory.  (default is standard output )

     -htrhd_keyword
          Enter the trace header keyword  upon  whose  value  the
          taper  (and  mutes) will be based. Typical values might
          include DstSgn, DphInd, RecNum, SrcLoc, and RecInd.

     -startupstartup
          Start of the upward portion of the taper/ramp in  units
          appropriate for the the trhd_keyword.

     -endupendup
          End of the upward portion of the  taper/ramp  in  units
          appropriate for the the trhd_keyword.

     -startdownstartdown
          Start of the downward  portion  of  the  taper/ramp  in
          units appropriate for the the trhd_keyword.

     -enddownenddown
          End of the downward portion of the taper/ramp in  units
          appropriate for the the trhd_keyword.

     -L   If present, calculate taper using Linear weights of the
          form,        w(x)=(x-startup)/(endup-startup)        or
          w(x)=(enddown-x)/(enddown-startdown)              where
          x=trhd_keyword.


     -H   If present, calculate taper using  Hamming  weights  of
          the   form,   w(x)=0.54+0.46*cos(y),  where  y=2*pi*(x-
          startup)/(endup-startup)      or       y=2*pi*(enddown-
          x)/(enddown-startdown) where x=trhd_keyword.

     -B   If present, calculate  taper  using  Blackman  weights,
          w(x)=0.42+0.5*cos(y)+0.08*cos(2y),    where  y=2*pi*(x-
          startup)/(endup-startup)       or       y=2*pi(enddown-
          x)/(enddown-startdown) where x=trhd_keyword.

     -V   Verbose mode.  All parameters from the command line and
          lineheader will be sent to standard error output.

     -?   Query mode.  With this flag, taper will send a descrip-
          tion  of  the  command  line  arguments to the standard
          error output and stop.

BUGS

     No trap for running program without an input file and  noth-
     ing in the standard input.

PROJECT AGREEMENT:

     518, Seismic Signal Analysis.

EXAMPLE:

     This program was originally written  to  facilitate  merging
     overlapping  mbs  output from portions of a Hainan line shot
     with different parameters (in this case the shooting  direc-
     tion).
     Given the following two lines having the same migrated (possibly zero) offsets :
     mbs_sort.1a  with live data covering crp (DphInd) 1-2000.
     mbs_sort.1b  with live data covering crp (DphInd) 1500-3500.
     we merge them by running the following:
     taper -Nmbs_sort.1a -hDphInd -startdown1500 -enddown2000 -L -Ombs_sort.1a_taper
     taper -Nmbs_sort.1b -hDphInd -startup1500 -endup2000 -L -Ombs_sort.1b_taper
     vstak -N1mbs_sort.1a_taper -N2mbs_sort.1b_taper -amp1. -Ombs_sort.1.merged

AUTHOR:

      K. J. Marfurt (APR, 1994).

COPYRIGHT

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