NAME

     sis_xy  - turn usp format trace data into x-y pairs (or  the
     reverse)

SYNOPSIS

     sis_xy [ -Nntap ] [ -sist ] [ -eiend ] [ -iidec ] [  -nsnstr
     ]  [ -nenetr ] [ -T0tdel ] [ -rsnrst ] [ -renred ] [ -R0rdel
     ] [ -fdels ] [ -bncomp ] [ -wwvel ] [ -B ] [ -M ] [ -R  ]  [
     -nvnullval  ]  [ -nsampnsamp ] [ -ntrcntrc ] [ -nrecnrec ] [
     -V ] [ -? ]

DESCRIPTION

     sis_xy in forward mode: takes as its input usp format  trace
     data and outputs a selected portion of this to stdout in the
     form of pairs (essentially a  time  index  followed  by  the
     amplitude).   Each trace is separated by a blank line.  This
     output may be plotted in x-windows by xgraph. If a  previous
     sis_xy   (in  reverse  mode) was used to create the data set
     then the line header contains entries to duplicate the first
     column  (X).  The  trace  amplitudes  of  course produce the
     second column (Y).

     sis_xy in reverse mode: takes as its input  a  file  of  X-Y
     pairs  (one  pair  per  line) and converts them to a seismic
     format trace. If groups of these pairs are  separated  by  a
     null  or  blank  line  they  will  be considered as separate
     traces. In that case each group of X-Ys must have  identical
     numbers  of  entries. Information about the first column (X)
     is stored in the line header, e.g. first X value and  the  X
     increment, assuming regular spacing of the X values.

     In forward mode there are two formats of  output  available:
     (1)  read  in each trace, window, then output time-amplitude
     pairs ending with a null line; (2)  read  in  traces  betwee
     ns,ne, window in time, then write out amplitudes in columns,
     one per trace.

     sis_xy gets both its data and its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the trace window, the start  and  end  traces,  and  verbose
     printout, if desired.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing  -N.  In  forward  mode this will be the seismic
          data set which can be a pipe. In reverse  mode  if  the
          input  is  piped  then the number of trace samples, the
          number of traces per record, and the number of  records
          must be specified on the command line.  This input 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 '/b/vsp'.

     -O ntap
          Enter the output data  set  name  or  file  immediately
          after  typing  -O.  In  reverse  mode  this will be the
          seismic; in forward mode this is the file of X-Ys. Both
          may be piped out.

     -s ist
          Forward mode: enter the start time of the output trace.
          The default is the beginning of the trace.

     -e iend
          Forward mode: enter the end time of the  output  trace.
          The default is the end of the trace.

     -i idec
          Forward mode: ehe output sample increment.  Default = 1

     -ns nstr
          Forward  mode:  enter  the  start  trace  number.   The
          default is the first trace of the record.

     -ne netr
          Forward mode: enter the end trace number.  The  default
          is the last trace of the record.

     -T0 tdel
          Forward mode: ehe output trace increment (can only skip
          forward  -  if you need to skip backwards use editt and
          pipe into sis_xy).  Default = 1

     -rs nrst
          Forward mode: enter start record number.  Default value
          is the first record.

     -re nred
          Forward mode: enter end record number.   Default  value
          is last record.

     -R0 rdel
          Forward mode: ehe output  record  increment  (can  only
          skip  forward - if you need to skip backwards use editt
          and pipe into sis_xy).  Default = 1

     -f dels
          Forward mode: enter sample interval override.   Default
          is input sample interval.

     -b ncomp
          Forward mode: basically a different  type  of  display:
          windowed data for each selected input record are output
          in ncomp columns (as a function of time  which  is  the
          first  column).  ncomp  is  the number of data columns.
          This should be a small (<10) value.

     -w wvel
          Forward mode: do not output any trace values at the top
          of  the trace that are less than this value. Useful for
          not outputting say the water column of a velocity  data
          set. Default is to output all valid samples.

     -B   Forward mode: enter the command line argument  '-B'  to
          suppress null lines between traces.  xygraph interprets
          null lines as separators and will then change colors on
          the plot.  Otherwise it will overplot.

     -M   Forward mode: enter the command line argument  '-M'  to
          read  the  MBS  depth interval line header word and use
          this as the sample interval.

     -R   Enter the command line  argument  '-R'  to  invoke  the
          reverse  mode,  i.e. reading a file of X-Ys and output-
          ting seismic.

     -nsamp nsamp
          Reverse mode: specify the number of samples per  trace.
          If  the  input XYs are piped then this must be given on
          the command line; if the input XYs are in a  disk  file
          then  this  entry  is an override. This will change the
          line header but the actual number of non  zero  samples
          output will be determined by the input stream, i.e. the
          number of samples between null lines.

     -ntrc ntrc
          Reverse mode: specify the number of traces per  record.
          If  the  input XYs are piped then this must be given on
          the command line; if the input XYs are in a  disk  file
          then  this  entry  is an override. This will change the
          line header but the actual number of output traces will
          be  determined  by  the  number  of traces in the input
          file.

     -nrec nrec
          Reverse mode: specify the number  of  records.  If  the
          input XYs are piped then this must be given on the com-
          mand line; if the input XYs are in  a  disk  file  then
          this  entry  is  an override. This will change the line
          header but the actual number of output records will  be
          determined  by  the number of full records of traces in
          the input file.


     -nv nullval
          Reverse mode: this is a value that if it occurs in  the
          input will be zeroed on output. Default = 0.0

     -V   Enter the command line argument '-V' to get  additional
          printout.

     -?   Enter the command line  argument  '-?'  to  get  online
          help.   The program terminates after the help screen is
          printed.

EXAMPLES

     (1) Forward mode

     sis_xy -Nseis_in -T04 | xgraph

     where every fourth trace of the input seismic data  is  con-
     verted to X-Y pairs and sent to the X-Y plot program.

     (2) Reverse mode

     sis_xy -Nlog_data -Oseis_log

     where log data consisting of  depth-travel  time  pairs  are
     converted into a seismic trace.

BUGS

     unknown

AUTHOR

     Paul Gutowski, (socon 422-3146), zprg03@trc.amoco.com

COPYRIGHT

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