EdgeTech's SEG-Y to SIOSEIS's SEG-Y

One of the most important differences in the X-Star's SEG-Y is
that the data are "raw matched filtered" or "evelope data" and
are complex numbers rather than real numbers.  SIOSEIS process 
GAINS parameter TYPE 7 converts complex numbers to real numbers.

Using process prout to dump SEG-Y trace header words 1, 3, 4, 5, 6, 7
shows several other differences:

  SIOSEIS ver 99.6 (5 September 1999)  (C) Regents of U.C.                       
 procs diskin prout end 
 diskin 
    ipath tape_6.raw.segy end 
  ***  WARNING  ***  RP is zero and RP trace number is non-zero.
  DISKIN thinks this file is sorted by RP.
  Use DISKIN parameters NO and TR or SORT to read properly.
  Use process HEADER to set the rp trace number to 0.
 end 
 prout 
    indices l1 l3 l4 l5 l6 l7 
     fno 0 lno 99999 ftr 0 ltr 999 end 
 end 
 end 
 ****    0 ERRORS IN THIS JOB   ****
      12308.    0.0000     0.0000     0.0000     0.0000      1.0000
      12308.    0.0000     1.0000     0.0000     0.0000      1.0000
      12309.    0.0000     0.0000     0.0000     0.0000      1.0000
      12309.    0.0000     1.0000     0.0000     0.0000      1.0000
      12310.    0.0000     0.0000     0.0000     0.0000      1.0000
      12310.    0.0000     1.0000     0.0000     0.0000      1.0000
      12311.    0.0000     0.0000     0.0000     0.0000      1.0000
      12311.    0.0000     1.0000     0.0000     0.0000      1.0000
      12312.    0.0000     1.0000     0.0000     0.0000      1.0000
      12312.    0.0000     0.0000     0.0000     0.0000      1.0000
      12313.    0.0000     1.0000     0.0000     0.0000      1.0000
      12313.    0.0000     0.0000     0.0000     0.0000      1.0000
      12314.    0.0000     0.0000     0.0000     0.0000      1.0000
      12314.    0.0000     1.0000     0.0000     0.0000      1.0000
      12315.    0.0000     1.0000     0.0000     0.0000      1.0000
      12315.    0.0000     0.0000     0.0000     0.0000      1.0000

       l1       l3         l4         l5         l6          l7
     rec no     shot no    shot tr    energy pt  CDP no      CDP tr
     

The EdgeTech documentation for "X-STAR FULL SPECTRUM SUB-BOTTOM PROFILER", page 4-10 defines
their use of the SEG-Y trace header as:

 Integer No	Description
0-1			Trace (record) number (integer - 32 bit)
14			Trace identification
.
.
93			NMEA hour
94			NMEA minutes
.
.
100-101		Trace scale factor (floating point)


Note that there is no millisecond.

There are several models of EdgeTechs, this one apparently has
two hydrophone outputs, one a single phone and the other
beamformed from four hydrophones.  Use the single phone for
very shallow horizons.

Notice that SEG-Y word four seems to be a trace number within the
shot, though the trace order seeme to be reversed occasionaly.
SIOSEIS wants the shot number to be in SEG-Y word 4.  SIOSEIS
also expects the traces to be numbered 1, 2 rather than 0, 1.
Another problem is that SIOSEIS uses word 7, the CDP trace number
to indicate that the data are sorted by CDP or RP, so EdgeTech's
1 in word 7 will be a problem.

Another "gotcha" is contained in the SEG-Y readable header that
says "Envelope Sample interval = A/D/ Sample Interval*2".  The
SEG-Y data is envelope data and not A/D data, so the SEG-Y sample
interval is wrong for the data in the file!

lsd tape_6.raw.segy 1 11
      SHOT   TR       RP    TR ID  RANGE DELAY NSAMPS    SI   YR DAY HR MIN SEC
         0     0       0     1  1      0     0   3976    20 1999 238 22  18   5
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     0       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     0       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     0       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     0       0     1  1      0     0   3976    20 1999 238 22  18   7
         0     1       0     1  1      0     0   3976    20 1999 238 22  18   7


EdgeTech has used SEG-Y unused bytes 201-204 (EdgeTech 100-101)
to store the "Trace scale factor".  SIOSEIS uses the same bytes
(SIOSEIS word 51) as an "end-of-gather" flag.

SIOSEIS process HEADER parameters:
 header
    fno 0 lno 999999 ftr 0 ltr 99999
    l3 = l1 l4 = l4 + 1 l7 = 0 i59 = i59 * 2 
    r49 = r49 * 2 r55 = r51 r51 = 0 end
 end

will changed the EdgeTech SEG-Y to SIOSEIS SEG-Y.
l3 = l1 copies the EdgeTech record number to the shot number.
l4 = l4 + 1 increments the shot trace number so it is 1 or 2
            rather than 0 or 1.
l6 = 0  sets the CDP trace number to 0.
i59 = i59 * 2 corrects the SEG-Y sample interval
r49 = r49 * 2 corrects sioseis's floating point sample interval
      diskin calculated.
r55 = r51 copies the EdgeTech trace scale factor to word 55.
r51 = 0  sets SIOSEIS's end-of-gather flag to zero.


SIOSEIS process GAINS converts complex traces to real traces:
gains
   type 7 end
end

The EdgeTech trace scalar MUST be applied since it can change
on every trace.

The new SIOSEIS process WEIGHT parameter HDR will multiply all trace
amplitudes by the trace scale factor:
weight
   fno 0 lno 999999 hdr 55 end
end


The script to read and convert EdgeTech files is:
sioseis << eof
procs diskin header gains weight diskoa prout end
diskin
   ipath tape_6.raw.segy end
end
 header 
    fno 0 lno 99999 ftr 0 ltr 99999 
    l3 = l1 l4 = l4 + 1 l7 = 0 r55 = r51 r51 = 0 end 
 end 
gains
   type 7 end
end
weight
   fno 0 lno 999999 hdr 55 end
end
diskoa
   opath data end
end
plot
   nibs 75 vscale 150 nsecs .1 tlines .01 .05 .1
   srpath sunfil
   def .02 end
end
prout
    fno 0 lno 99999 ftr 0 ltr 999 end
end
end
eof