PROCESS IRIS

Document Date: 13 May 1990

Convert IRIS data logger data into standard SEG-Y formatted data.  It is 
assumed that all the data input through PROCESS DISKIN in a single job are a
"single event".  The DISKIN parameter FORMAT may be used to read the IRIS
data traces.

This does the following:

1)   This process will make the data into SIOSEIS type RP sorted data.  That
     is, it will increment the rp trace number by 1 until the end of the job.
     The last trace does NOT have the SIOSEIS end of gather flag set, so it
     may be prudent to read any rp's produced with PROCESS DISKOX with the 
     DISKIN parameter FORGAT.

2)   PROCESS IRIS will also correct the shot times (the time of the first 
     sample - recorded in the SEG-Y trace header as GMT) to be at the same 
     GMT rather than the IRIS trigger time.  The milliseconds field of the 
     GMT is also dropped.  This should make timing a little easier to see on
     a seismic plot.  On output, all data is relative to the GMT in the SEG-Y
     header.   Procedurally this process uses the GMT of the first trace
     encountered, subtracts 1, and uses that as the output time reference 
     (ignoring the milliseconds). e.g.
     trace 1 has day 110 hour 2 min 24 sec 51 mil 107 
     trace 2 has day 110 hour 2 min 24 sec 50 mil 974
     trace 3 has day 110 hour 2 min 24 sec 51 mil 2
     then the output GMT is set to day 110 hour 2 min 24 sec 50
     and trace 1 has a delay of 1.107, trace 2 has a delay of 0.974,
     trace 3 has a delay of 1.002
      
****  NOTE   ****
     The data is time shifted.

COPYRIGHT (C) The Regents of the University of California
ALL RIGHTS RESERVED.  
Written by Paul Henkart, Scripps Institution of Oceanography, 6 May 1990