NAME
dmoangst3d - 3D angle stack
SYNOPSIS
dmoangst3d [ -Nntap ] [ -Ootap ] [ -vvtap ] [ -attap ] [
-Aatap ] [ -Tttap ] [ -dexpdexp ] [ -dincinca ] [ -emergiem
] [ -modemode ] [ -R ] [ -dmindstmin ] [ -dmaxdstmax ] [
-ddeldstdel ] [ -x1x1 ] [ -y1y1 ] [ -x2x2 ] [ -y2y2 ] [
-x3x3 ] [ -y3y3 ] [ -x4x4 ] [ -y4y4 ] [ -cldmcldm ] [ -ild-
mildm ] [ [ -diminmindi ] [ -dimaxmaxdi ] [ -liminminli ] [
-limaxmaxli ] ] [ -AS ] [ -CSA ] [ -COA ] [ -BKA ] [ -GS ] [
-V ] [ -? ]
DESCRIPTION
dmoangst3d incorporates both the angle stacking and DMO
found in angst3d and dmostk3d respectively. As each trace
arrives it's cell is identified from its source and receiver
XYs and its offset and the DMO swath of cells along the line
joining S-R is defined. The amplitudes of the input trace
are then sprayed out along DMO ellipses in the plane of the
swath. These dmo'd traces for this offset are then angle
stacked into the output data set which accumulates the
amplitudes with all cells and for all angle ranges.
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 of a size equal to N
times a stacked volume (N being the number of angle ranges
asked for), (3) a third disk file will be necessary to hold
the pre-computed angles, one set at each bin and of a size
equal to the number of cells x the number of model offsets x
the number of samples in each angle trace. These files can
all be on separate disk partitions.
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.
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.
dmoangst3d gets both its data and its parameters from com-
mand 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 intermediate angles file (stored in seismic
trace format). 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 determined by linearly interpo-
lating the stored angle traces on either side of the
current trace offset. The angles then determine which
samples from the input trace will be stacked. The deci-
mation factor is given by inca (default=10, see below).
This file is of size (# cells) x (# model offsets) x (#
samples). Since angles vary smoothly with offset the
model offset increment can be several times (>4) larger
than the actual group interval saving both time and
disk space. No default.
-T ttap
Enter the name of the disk file containing the normali-
zation data in seismic trace format. 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 X (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 Y (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).
-ddel dstdel
Enter the offset increment of the model spread (in
ft,m). No default. At a given time angles are linearly
interpolated between the model spread distances to get
the angles for the current input trace offset. Since
angles vary smoothly this can be several (>4) times
larger than the group interval. This reduces the size
of the angles file on disk. This value can be several
times larger (>4) than the actual group interval since
the angle functions change slowly enough with distance
to use interpolation to get the angle function
corresponding to the input trace offsets.
-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.
-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 = 1.0
-AS If present on the command line turn off the anti alias
constraints and process all
dips.
-CSA If present on the command line apply common shot ampli-
tude term. This is also the default. Note: either this
option or the common offset option below both preserve
amplitudes well; use of the kinematic term will not be
so nice to the amplitudes but the code will run some-
what faster. Default is to use no amplitude term.
-COA If present on the command line apply common offset
amplitude term.
-BKA If present on the command line apply Kirchhoff
kinematic amplitude term.
-GS If present on the command line use geometric spread,
otherwise zero offset spreadi ng will be used.
-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 | \
dmoangst3d -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 | \
dmoangst3d -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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