NAME
swath_design - a routine to aid in the design of corner
coordinates required when processing large 3D data volumes
in more than a single swath.
SYNOPSIS
swath_design [ -nrecnrec ] [ -ntrcntrc ] [ -nsampnsamp ] [
-diskGbyte ] [ -ildmildist ] [ -cldmcldist ] [ -ilazimde-
grees ] [ -clazimdegrees ] [ -ndinum_DI ] [ -nlinum_LI ] [
-padoverlap ] [ -x1xcoord ] [ -y1ycoord ] [ -Xxgraphfile ] [
-V ] [ -? or -h ]
DESCRIPTION
swath_design requires input of enough information to define
the LI,DI geometry, the amount of data involved and the
amount of disk space available for processing. With this
information the routine will determine the number of swaths
required to process the data and output the corner coordi-
nates for each swath. It is advisable to provide an ade-
quate overlap between swaths to ensure full fold in each
swath. This is not to say that data from each swath will be
used more that once. The overlap is to make sure that all
data from within a single swath actually finds it's way into
the sr3d2 volume. Say you design swaths some 50 LI's wide
that require for example 25 input sail lines to create.
Upon running sr3d1 if your fold record shows that you have
not dropped to zero fold on the boundaries of your swath
then you should use a larger overlap. When doing swath pro-
cessing it is manditory that all swaths emanate from a com-
mon corner 1. In all the USP binning routines [sr3d1,
sr3d2, dbvec, edit3d] the bin centers are calculated from
the (X1,Y1) corner. If you do not use a common corner to
generate your swath geometry you may run into trouble when
merging the swaths post-stack. You may see fold striping
going on as the bin centers get out of sync between swaths.
This routine assures that that does not happen.
All pertinent swath information is printed to the printout
file. If flagged for verbose printout [-V] this information
will also appear on the screen. An optional xgraph file may
be requested to provide a graphical representation of your
swath design. It is best to plot this using xgraph -P so
that the corner points are obvious.
swath_design gets its parameters from command line argu-
ments. These arguments specify the the number of records,
traces and samples in the shot data going into the 3D
volume. You can report this as simply the number of traces
if you want by setting the number of records to 1 and the
number of traces to however many millions of traces you
have. Also specified on the command line are the desired
size of each swath on disk, the number of LI's and DI's in
the overall 3D volume, the LI and DI increment in the units
of your survey, the in-line and cross-line azimuths of your
survey, the reference (x,y) coordinates for corner 1 of
swath1, the filename of an optional xgraph output file and a
verbose output flag.
Command line arguments
-nrec nrec [default: 1]
Enter the number of shot records in the 3D dataset. If
you only know the total number of traces then leave
this default to unity.
-ntrc ntrc [default: 1]
Enter the number of traces per shot record in the 3D
dataset. If you wish to tell the routine the total
number of traces then set -nrec to unity [the default]
and report the total number of traces in the volume
here.
-nsamp nsamp [default: 1]
Enter the number of samples per trace in the 3D volume.
-disk Gbyte [default: none]
Enter the desired swath disk file size [in Gbytes].
-ildm ildist [default: 12.5]
Enter the in-line [side 1 - 2] spacing in the units of
your survey.
-cldm cldist [default: 40.0]
Enter the cross-line [side 1 - 4] spacing in the units
of your survey.
-ilazim degrees [default: none]
Enter the in-line [side 1 - 2] azimuth in degrees.
This routine sees zero degrees as North.
-clazim degrees [default: none]
Enter the cross-line [side 1 - 4] azimuth in degrees.
This routine sees zero degrees as North.
-ndi num_DI [default: none]
Enter the number of bins in the in-line direction [side
1 - 2] of your survey. This is the total number of
DI's used for the overall survey.
-nli num_LI [default: none]
Enter the number of bins in the cross-line direction
[side 1 - 4] of your survey. This is the total number
of LI's to be used for the overall survey. The number
of LI bins per swath will be calculated based on this
value.
-pad overlap [default: 0]
Enter the number of LI's to pad on either side each
swath. This provides an geometric overlap between
swaths to assure that all data from within the swath
makes it to the sr3d2 volume. To verify that your pad
was large enough you may examine the nominal fold out-
put from sr3d1 and make certain that you have at least
one LI with zero fold everywhere on either side of your
swath. If you do not then you may have clipped some
data from your survey and may result in a seam when you
merge your swaths post-stack. Too large a pad is
better than too small a pad in that you can always use
edit3d to surve up a range limited version of your
sr3d2 volume for binning purposes.
-x1 xcoord [default: 0.0]
Enter the x coordinate in the units of your survey of
corner 1 for the first swath of your survey. All sub-
sequent dimensions will be projected from this point
thereby insuring that your bin centers remain on the
same sampling grid for every swath. If this is not
true you may have problems with fold striping [0 - 3 -
2 - 1 instead of 1 - 2 - 2 - 1] merging the swaths
post-stack.
-y1 ycoord [default: 0.0]
Enter the y coordinate in the units of your survey of
corner 1 for the first swath of your survey. All sub-
sequent dimensions will be projected from this point
thereby insuring that your bin centers remain on the
same sampling grid for every swath. If this is not
true you may have problems with fold striping [0 - 3 -
2 - 1 instead of 1 - 2 - 2 - 1] merging the swaths
post-stack.
-X xgraphfile [default: not used]
Enter the filename of an optional output xgraph file.
This file if requested will contain the corner coordi-
nates for all swaths in xgraph format so that you can
quickly see a graphical representation of your swath
configuration. When plotting this file with xgraph use
the -P option in order to make the various corner
points more obvious.
-V Enter the command line argument '-V' to get additional
printout.
-? or -h or -help
Enter the command line argument '-?' or -h or -help
to get online help. The program terminates after the
help screen is printed.
DISCUSSION
If you wish to use this routine to design the corner coordi-
nates of your survey for a single swath then simply default
the volumetric parameters -nrec, -ntrc, -nsamp and make the
size of the disk volume large -disk32. This will of course
result in the entire volume fitting in a single swath. An
example of the command line usage would be:
swath_design -nrec1436 -ntrc320 -nsamp1501 -disk29 -ildm12.5
-cldm40.0 -ilazim144 -clazim234 -x1 183612 -y1 26452
-Xtest1 -V -nli74 -ndi1395
output from the above would look like:
Swath Calculations
------------------
number of swaths required = 1
number of LIs per swath = 74
Swath Corner Report
-------------------
Swath 1
-x1 183612. -y1 26452.
-x2 193862. -y2 12345.
-x3 191467. -y3 10605.
-x4 181217. -y4 24712.
Notice that the corner coordinates are displayed in USP com-
mand line syntax. This makes it easy to cut and paste these
coordinates right into the sr3d1, dbvec or vi3d command
lines.
BUGS
unknown.
SEE ALSO
sr3d1(1) sr3d2(1) dbvec(1) edit3d(1) vi3d(1)
AUTHOR
[P.G.A. Garossino: Socon 422-3932]
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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