NAME
angst3d - 3D angle stack
SYNOPSIS
angst3d [ -Nntap ] [ -Ootap ] [ -vvtap ] [ -attap ] [ -Aatap
] [ -Tttap ] [ -dexpdexp ] [ -dincinca ] [ -emergiem ] [
-modemode ] [ -R ] [ -dmindstmin ] [ -dmaxdstmax ] [ -x1x1 ]
[ -y1y1 ] [ -x2x2 ] [ -y2y2 ] [ -x3x3 ] [ -y3y3 ] [ -x4x4 ]
[ -y4y4 ] [ -cldmcldm ] [ -ildmildm ] [ [ -diminmindi ] [
-dimaxmaxdi ] [ -liminminli ] [ -limaxmaxli ] ] [ -norm ] [
-shot ] ] [ -V ] [ -? ]
DESCRIPTION
angst3d is a simple NMO correction and CDP bin angle stack
designed for either marine or land data. An optional plain
vanilla NMO (quadratic interpolation) can made to the data
before angle stacking. Provision is made for distance lim-
iting the stack to the limits defined by the user in the
model spread. The model spread distances and the velocities
govern the ray tracing and hence the stacking angles.
Space on disk must be found for several copies of the stack
volume: (1) the output file will be n stacked volumes for
the n angles (can either be all in one file or distributed
one angle per file, (2) a normalization file equal in size
to the combined stacked output files, (3) a third disk file
will be necessary to hold the pre-computed angles, one set
at each bin. These files can all be on separate disk parti-
tions.
The input data can be in any sort order (shot, group, cdp,
offset) but must at least have the source X-Ys (SrPtXC and
SrPtYC) and the receiver X-Ys (RcPtXC and RcPtYC) trace
header words properly filled in since these are are critical
to calculating where the trace belongs. The SrRcMX and
SrRcMY are optional since they can be calculated internally.
For data in shot order it is assumed that the basic correc-
tions have been made, e.g. refraction statics, velocity
analysis, residual statics. Other processes such as deconvo-
lution and coherent noise filtering can be done on the fly
before input into the cdp bin stack.
angst3d gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
the cdp velocity, output survey extent, optional range and
azimuth reject limits, and verbose printout, if desired.
Command line arguments
-N ntap
Enter the input data set name or file immediately after
typing -N unless the input is from a pipe in which case
the -N entry must be omitted. This input file should
include the complete path name if the file resides in a
different directory. Example -N/b/vsp/dummy tells the
program to look for file 'dummy' in directory '/b/vsp'.
-O otap
Enter the output cdp stack data set name(s) or file(s)
immediately after typing -O. You can either have a
single output file in which case the number of output
records will be equal to the number of cells in the
survey defined below, or you can have a number of out-
put files equal to the number of angle pairs (e.g. -O[]
-O[] -O[] for 3 angle pairs) in which case the number
of traces will be equal to 1 and each data set will be
for a specific angle. The output file(s) must be disk
file(s) and cannot be piped.
-v vtap
Enter the name of the RMS velocity disk file. The velo-
city field must have one velocity tape-format function
(trace) per bin location (the bins must correspond to
the output cdp stack bins). Even though there must be a
velocity function at every bin location but the func-
tion can be coarsely sampled in time (e.g. every
100ms). The cdp program will automatically resample the
coarse function using a cubic spline interpolator. The
velocity file must be on disk since the program does
random access seeks to extract the correct velocity (in
the case of a multiple function velocity file).
-A atap
Enter the input file name for the angle cards (only one
set allowed). The number of angle pairs will be termed
the number of angles. The format is 7(F5.0,F5.0) with
the first 5 columns reserved for 1ANGL, 2ANGL, ...,
9ANGL (9ANGL terminates the angle set (only one set
allowed). No default.
-a ttap
Enter the intermediary angles file. For each cell
(velocity) for the given spread geometry the angles are
pre-computed, decimated in time, and written into this
file. During the actual stacking process as each trace
is read from input its cell is deterimined and the
angle trace for that trace's offset is then read from
the angle file. The angles then determine which samples
from the input trace will be stacked. The decimation
factor is given by inca (default=10, see below). No
default.
-T ttap
Enter the name of the disk file containing the
normalization data. This will be about the same size as
the output stack data set(s) except it will be a single
file. This output cannot be piped.
x4, y4]
-x1, -y1, -x2, -y2, -x3, -y3, -x4, -
y4 [x1, y1, x2, y2, x3, y3,
Enter the area of interest over the survey with the X-Y
coordinates (ft,m) defining the four corners of a
parallelogram on the ground. Going either clockwise or
counter clockwise (clockwise recommended) from Corner 1
the first move to Corner 2 should be in the direction
of a receiver or shot line. The direction 1-2 will
always define the Y or DI direction. The DIs will
always start from side 1-4 and increase in the 1-2 (Y)
direction; the LIs will always start from side 1-2 and
increase in the 1-4 (X) direction. The values must be
the same units as those given in the source, receiver,
and midpoint X-Ys in the trace headers.
-cldm cldm
Enter the crossline (2-3 side) cell dimension (ft,m).
For most shooting geometries this will be 1/2 the group
or line spacing depending on the orientation of side
2-3 with respect to the receiver lines. No default.
-ildm ildm
Enter the inline (1-2 side) cell dimension (ft,m). For
most recording geometries this will be 1/2 the group or
line spacing depending on the orientation of side 1-2
with respect to the receiver lines. No default.
-dmin dstmin
Enter the minimum offset of the model spread (in ft,m).
No default. The size of the angle intermediate file
will be governed in part by the number of groups in the
model spread (the other part being the decimation fac-
tor - see below).
-dmax dstmax
Enter the maximum offset of the model spread (in ft,m).
No default. The size of the angle intermediate file
will be governed in part by the number of groups in the
model spread (the other part being the decimation fac-
tor - see below).
-limin, limax minli, maxli
Enter the minimum and maximum line indexes to output.
The output survey will have so many bins in the inline
direction and so many bins in the crossline direction.
This is a handy way to start and end outputting bins at
specified sequential inline numbers and for focussing
the analysis on a limited & more managable portion of
the survey. Default is the first and last inline bin as
determined from the 4 corners of the survey provided on
the command line.
-dimin, dimax mindi, maxdi
Enter the minimum and maximum crossline indexes to out-
put. The output survey will have so many bins in the
inline direction and so many bins in the crossline
direction. This is a handy way to start and end output-
ting bins at specified sequential crossline numbers.
Default is the first and last crossline bin as deter-
mined from the 4 corners of the survey provided on the
command line..
-dinc inca
Enter decimation factor for the stored angle traces.
The closer this gets to 1 the larger the intermediate
angle file will get (also governed by the number of
groups in the model spread). Default = 10
-emerg iem
Enter 0 for incident angle calculation, 1 for emergence
angle. Default = 0.
-mode mode
Enter 0 for straight ray solution, 1 for curved rays,
or 2 for perturbed rays. DefaUlt = 2
-R Enter the command line argument '-R' to restart a pre-
vious run that has stopped for some reason. The stderr
messages will announce every sequential record about to
be processed so the user can easily determine where in
the input data set the process stopped. By using suit-
able editt parameters the cdp run can be continued at
the point at which it stopped without the previous data
being wiped.
-norm
Enter the command line argument '-norm' to turn on
application of normal moveout on the data prior to
stack. Default is to assume NMO correction has already
been applied.
-dexp dexp
Enter the exponent for the normaization operation. Each
output cdp stack sample will be divided by the number
of live samples that created that stack sample raised
to the dexp power. Default = 0.7
-shot
Enter the command line argument '-shot' to tell the
program shot data is being input. Currently this option
does nothing.
-V Enter the command line argument '-V' to get additional
printout.
-? Enter the command line argument '-?' to get online
help. The program terminates after the help screen is
printed.
BUGS
No checks on the input trace headers to see if they have
valid source, receiver, or midpoint X-Ys.
EXAMPLE
1. cdp stack from disk input:
gather -N/data1/indat1 -N/data1/indat2 -N/data1/indat3 -S |
\
pred -p32 -ol200 -TV | \
angst3d -Ocdp1 -Ocdp2 -x13000 -y12000 -x20 -y23000 -x30 -y30
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -dmin0 -dmax6800 -ddel200
-aafile -Aacards -norm
where the the X-axis corresponds to the receiver lines and
we go counter clockwise starting from the upper right
(northeast) corner along a receiver line. The input data is
spread out over 3 disk partitions and we use gather to
assemble them in sequence. The input stream is also passed a
time varying predictive decon; the output is partitioned
into 2 files (in this case the angle card file contains 2
angle limit pairs). A model spread from 0 to 6800 (35
groups, group interval is 200) is used. Normal moveout will
be applied internally.
2. cdp from tape input:
xcram10 -r | \
angst3d -Ocdp -x13000 -y12000 -x20 -y23000 -x30 -y3 0
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -dmin0 -dmax6800 -ddel200
-aafile -Aacards -norm
where the input here is from a tape stacker accessed using
xcram10.
SEE ALSO
sr3d1, sr3d2, cdpstk3d
AUTHOR
Paul Gutowski (socon 422) 3146
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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