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      Fish datum correction using an XYZ file

First put the water depth into SEG-Y header 16 while converting
to SEG-Y format.  The interpolated floating point water bottom
two-way travel time is written into word 50.  The interpolated 
time must be used because the data are high enough frequency that
there are several samples per meter.

sioseis << eof
procs diskin xstar diskoa end
diskin
   format edgetech
    ipath /data/vol3/henkart//xstar_1999/yr1999day218-0016z.xstar END
end
xstar
   binpath xyz.bin   ! use a binary version of the XYZ file
    xyzpath Eureka.xyz  ! depth goes in long word 16
    deltad 20 end
END
diskoa
    opath yr1999day218-0016z.segy end
end
prout
  indices l3 l16 r50
   fno 0 lno 999999 ftr 0 ltr 9999 end
end
end
eof


Now pick the first arrival (the water bottom as seen from the fish).
Subtract the picked time from the theoretical time.  Use MIX to smooth
(average) the shifts from 20 adjacent pings.

sioseis << eof
procs diskin wbt filter header mix shift gains plot end
diskin
   set 0 .4 fno 99748 lno 8888888 allno no noinc 2
  ipath yr1999day218-0016z.segy end
end
header
  r59 = r50 - r60   ! subtract the picked time from the theoretical
  end
end
mix
    type 4 hdr 59 weight
    1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
    end
end
prout
  indices l3 l16 r50 r59 r60
    fno 0 lno 99999 ftr 0 ltr 999 end
end
shift
  indices r59 end
end
filter
     ftype 0 pass 500 1000 dbdrop 48 end
end
wbt    !  put the picked time in buf(60), normally it goes in 50
      index 60 thres .2e-08 track .05 end
end
gains
   tgp 0 1 .002 2  .03 4 .06 20 addwb yes end
end
plot
   stime .1
   nibs 2859 vscale 20 nsecs .2 tlines .01 .05 .1
   colors  gray opath siofil.gray
   wiggle 0 anninc 1 ann gmtint
   trpin 300 def .02 end
end
end
eof
sio2sun siofil.gray sunfil
xloadimage -r 90 sunfil &