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## Analysis of streamer feathering

```     This describes the analysis of streamer feathering and
SIOSEIS type 13 geometry.  The streamer navigation must be
described using the UKOOA P190 standard.

Given an unknown seismic line the first thing to do is
to plot the streamer position!  Using SIOSEIS and MATLAB, the
analysis follows:

1)  Create a synthetic SEG-Y file that contains the UKOOA
X-Y coordinates of the shot and receivers.
2)  Print the X-Y coordinates of the shot and receivers.
3)  Plot the streamer location using Matlab.
4)  Find the "start of line".
5)  Find the "end of line".
6)  Create a synthetic file with SIOSEIS geom type 13.
7)  Compare the feathering angle and crossline offset in the
SEG-Y header and the plots from step 3.
8)  Plot the crossline offsets vs survey distance.
9)  Plot the streamer feathering vs survey distance.

1)   Create a synthetic SEG-Y file that contains the UKOOA
X-Y coordinates of the shot and receivers.
sioseis << eof
procs syn geom diskoa end
syn
ntrcs 240 secs 1 fno 10479 lno 11050 tva .5 10000 1 end
end
geom
dbrps 12.5 navfil GOC14.240.p190 type 13 end
end
diskoa
opath syn.line14 end
end
end

2)  Print the X-Y coordinates of the shot and receivers.
more prt

#! /bin/csh
@ N = \$1
sioseis << eof
procs diskin prout end
diskin
fno \$N lno \$N
allno no ipath syn.line14 end
end
prout
indices l3 l4 l19 l20 l21 l22
format (6(1x,F10.0))
fno 0 lno 9999999
end
end
end

Comments:
Redirect stdout   (e.g.   prt 10579 > l.10579), then edit the output
file so that it conatins only numbers  (don't forget the last
line of the file).

3)  Plot the streamer location using Matlab.
load l.10579
x = l(:,5);
y = l(:,6);
a = min(x);
b = min(y);
x = x-a;
y = y-b;
sx = l(1,3) - a;
sy = l(1,4)-b;
plot(x,y,'b.',sx,sy,'r*')
axis([-1000 7000 -1000 7000])
grid on
title('10579')

Plots of the streamer at shots:
10579    10679    10779    10879    10979

4)  We really need to see the shot-line, so a similar sioseis job:
procs diskin prout end
diskin
fno 10601 lno 11000 ftr 1 ltr 1
allno no ipath syn.line14 end
end
prout
indices l3 l4 l19 l20 l21 l22 i48 i49
format (8(1x,F10.0))
fno 0 lno 9999999
end
end
end

and add to Matlab:
load l.all
ax = l(:,3) - a;
ay = l(:,4)-b;
hold
plot (ax,ay,'g-')

Plots of the streamer feathering are: 10779    10879    10979

Plots of the streamer cross-line offset are: 10779    10879    10979
```
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