NAME
li_di - given survey extent for each input trace compute LI
& DI indexes and store in header, optionally limit output
data, optionally, re-bin bin center XYs
-OR- given LI,DI indexes, compute bincenter X,Y's; or,
given X,Y's, compute LI,DI indexes.
SYNOPSIS
li_di [ -Nntap ] [ -Ootap ] [ -Fftap ] [ [ -flat ] [ -dimin-
mindi ] [ -dimaxmaxdi ] [ -liminminli ] [ -limaxmaxli ] ] [
-x1x1 ] [ -y1y1 ] [ -x2x2 ] [ -y2y2 ] [ -x3x3 ] [ -y3y3 ] [
-x4x4 ] [ -y4y4 ] [ -cldmcldm ] [ -ildmildm ] [ -LI1listrt ]
[ -DI1distrt ] [ -records ] [ -bcxy ] [ -f2m ] [ -m2f ] [ -L
] [ -reject ] [ -LIDI ] [ -shot ] [ -rcvr ] [ -cdp ] [ -stk
] [ -BLI ] [ -BRI ] [ -V ] [ -? ]
DESCRIPTION
li_di takes input seismc data and based on XY locations of
traces computes the CDP LI & DI location indexes and stuffs
these into the LinInd and DphInd header slots. The input
data itself can be in any sort order. Optionally the program
can be flagged to limit the output of data to XYs lying
within the given survey boundaries (either shot, group, or,
midpoint XYs). It is also possible to pass or reject a sub-
set of the given survey area using minimum and maximum LI
and DI parameterization. The program will also operate in a
mode which takes either record and trace numbers or LI and
DI numbers and computes bin center XY values and stores them
in CDPBCY & CDPBCY
The input seismic traces must have the source and receiver
XYs, RcPtXC, RcPtYC, SrPtXC, SrPtYC, properly filled in.
These coordinates must given in the same system as the
workstation event file if used.
Dead Traces that do NOT have valid (X,Y) information will
not be passed.
li_di also allows the input and output files to be flat
files containing a pair of numbers per line. The program
can operate in two modes for flat files: 1) input is X,Y
(coordinate) pairs, output is the corresponding LI,DI pairs;
or 2) input is LI,DI pairs, output is the corresponding bin
center X,Y pairs.
li_di gets both its data and its parameters from command
line arguments. These arguments specify the input and out-
put seismic files, survey corner locations, LI & DI limits,
and verbose printout, if desired.
Command line arguments
-N ntap
Enter the name of the input seismic data. Default is
to read from stdin.
NOTE: if using the -flat option, the input file is a
flat file containing either X,Y pairs (use the -LIDI
option), or containing LI,DI pairs (use the -BLI
option).
-O otap
Enter the name of the output seismic data. Default is
stdout.
NOTE: if using the -flat option, the output file is a
flat file containing either LI,DI pairs (use the -LIDI
option), or containing X,Y pairs (use the -BLI option).
-F ftap
Optional: enter the name of the output fold map (in USP
format, plots like a time slice). It will be output as
a single record of number of traces equal to the number
of LIs and number of samples per trace equal to the
number of DIs. If corner 1 of the survey was chosen as
the NE corner then if the fold record is plotted in
reverse then the upper right corner will be the NE
corner. NOTE: not valid with the -flat option.
-flat
This option tells the program that the ntap and otap
files are flat files, NOT USP format seismic files.
Each line of the files contain a pair of values. This
option works with the -LIDI option to input X,Y pairs
and compute LI,DI indexes, or with the -BLI option to
input LI,DI indexes and compute bin center X,Y pairs.
-x1,-y1,-x2,-y2,-x3,-y3,-x4,-y4 [x1,y1,x2,y2,x3,y3,x4,y4]
Enter the area of interest over the survey with the X-Y
coordinates (ft,m) defining the four corners of a paral-
lelogram 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
increasing LI. From Corner 2 to Corner 3 should be in
the direction of increasing DI. These values must be the
same units as those in the trace headers.
-cldm cldm
Enter the crossline (along X or side 2-3) cell dimen-
sion (ft,m). For most shooting geometries this will be
1/2 the line or group spacing depending on the orienta-
tion of side 2-3 with respect to the receiver lines.
The sides are defined to be X along side 1-4 (roughly
cross-line direction), Y along side 1-2 (roughly in-
line direction). Remember when setting up the
coordinate system the line joining Corner (1) to Corner
(2) should be in the direction of a receiver or shot
line (i.e. the LI orientation). No default.
-ildm ildm
Enter the inline (along Y or side 1-2) cell dimension
(ft,m). For most recording geometries this will be 1/2
the line or group spacing depending on the orientation
of side 1-2 with respect to the receiver lines. The
sides are defined to be X along side 1-4 (roughly
cross-line direction), Y along side 1-2 (roughly in-
line direction). Remember when setting up the coordi-
nate system the line joining Corner (1) to Corner (2)
should be in the direction of a receiver or shot line.
No default.
-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. Default is the
first and last inline bin as determined from the 4
corners of the survey provided using the (x,y) entries
on the command line.
NOTE: not valid with the -flat option.
-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 using
the (x,y) entries on the command line.
NOTE: not valid with the -flat option.
-LI1 listrt
Enter the starting LI number. This is useful if you do
not want your output volume to arbitrarily start at LI
1. Say you wanted it to start at LI 25 then enter -
LI1 25 . Default = 1
NOTE: not valid with the -flat option.
-DI1 distrt
Enter the starting DI number. This is useful if you do
not want your output volume to arbitrarily start at DI
1. Say you wanted it to start at DI 25 then enter -
DI1 25 . Default = 1
NOTE: not valid with the -flat option.
-records
Enter the command line argument '-records' to limit
shot, receiver, or midpoint data based on whole
records. In accept mode if even one trace lies within
the XY limits then the entire record is accepted. The
only option available currently is the renumber -LIDI
option.
NOTE: not valid with the -flat option.
-bcxy
Enter the command line argument '-bcxy' to compute bin
center XYs given source and receiver XY. This is to be
used with -records and -cdp flags set. Each CDP record
is read and the midpoints for all live traces is com-
puted. The bin center XY for all traces in this gather
is then the average of the midpoints.
NOTE: not valid with the -flat option.
-f2m Enter the command line argument '-f2m' to scale the
workstation event XYs from feet to meters. The default
is no scaling.
NOTE: not valid with the -flat option.
-m2f Enter the command line argument '-m2f' to scale the
workstation event XYs from meters to feet. The default
is no scaling.
NOTE: not valid with the -flat option.
-L Enter the command line argument '-L' to limit the out-
put of data to those trace with XYs lying within the
survey boundaries as specified on the command line
using the (x,y) entries above. If you have also used
the min and max LI and DI command line entries no trace
with an LI or DI outside that range will be output.
You may also reject data from this interval [see
-reject below].
NOTE: not valid with the -flat option.
-reject
Enter the command line argument '-reject' in concert
with '-L' to reject data within the specified survey
area entered on the command line using the (x,y)
entries above. If you have also used the -minli,
-maxli -mindi -maxdi options no trace with an LI or DI
in that range will be passed.
NOTE: not valid with the -flat option.
-LIDI
Enter the command line argument '-LIDI' to put new LI &
DI numbers in the trace headers according to source,
receiver, or midpoint XYs (-shot or -rcvr or -cdp
flags). This option does no limiting even though it
uses a portion of the limit option code.
NOTE: using the -flat option, this argument flags the
input flat file as containing X,Y pairs, and the output
flat file will contain corresponding LI,DI values.
-shot
Enter the command line argument '-shot' to limit based
on shot XYs
NOTE: not valid with -flat option
-rcvr
Enter the command line argument '-rcvr' to limit based
on group XYs
NOTE: not valid with -flat option
-cdp Enter the command line argument '-cdp' to limit based
on midpoint XYs
NOTE: not valid with -flat option
-stk Enter the command line argument '-stk' if input data to
be limited is a stacked volume (-cdp is assumed). With
this option the CDPBCX and CDPBCY trace headers are
used for XYs. Note: some care should be taken regarding
dead traces in your input stack. If there are trace
marked dead (StaCor = 30000) then they can still be
recognized as valid input traces if their CDPBCX and
CDPBCY coordinates are not 9999999. Sometimes though
dead traces do not have valid coordinates. If you still
want to include them and you have valid record and
trace numbers in all the traces then run the stack
volume through li_di -BRI using the original survey
corners (not the limiting ones). This will recompute
the CDPBC coordinates for all traces.
NOTE: not valid with -flat option
-BLI Enter the command line argument '-BLI' to compute new
bin center XYs based on existing LI & DI numbers in the
input headers. The new values are written to the CDPBCX
and CDPBCY trace header slots. No limiting or re-
computation of the LI/DIs is done.
NOTE: when using the -flat option, this argument flags
the input flat file as containing LI,DI pairs, and the
output flat file will contain corresponding bin center
X,Y pairs.
-BRI Enter the command line argument '-BRI' to compute new
bin center XYs based on existing record & trace (RecNum
& TrcNum) numbers in the input headers. The new values
are written to the CDPBCX and CDPBCY trace header
slots. No limiting or re-computation of the LI/DIs is
done.
NOTE: not valid with the -flat option.
-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.
EXAMPLE 1:
li_di -Nindata -Ooutdata -x13000 -y12000
-x20 -y22000 -x30 -y30
-x43000 -y40 -ildm50 -cldm100 -f2m
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 trace
XYs are scaled from feet to meters.
DISCUSSION
When dead traces are not passed some grief may result if it
is important to retain record boundaries in subsequent pro-
cessing. If you fall into this category then there are
several things you can do. One solution is to pass your
data through bridge which will automatically pad the
required dead traces back in. In this case no bridge com-
mand line trickery is required. Simply pipe through bridge
data=stdin: format=usp out=tmp: out_data=stdout: . Another
approach would be to create an sr3d2 volume from the output
which you could use from this point on in the processing.
Another approach is to call us with your specific problem
and we'll give you a hand.
EXAMPLE 2:
li_di -Nindata -Ooutdata -x13000 -y12000
-x20 -y22000 -x30 -y30
-x43000 -y40 -ildm50 -cldm100 -flat -LIDI
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.
DISCUSSION
This example flags the input and output files as being flat
files containing 1 data pair per line. The above example
would have coordinate X,Y pairs as input. The output would
have the corresponding LI,DI pairs.
SEE ALSO
sr3d1, sr3d2, dbvec, edit3d
AUTHOR
Paul Gutowski (socon 422) 3146, Paul Garossino (socon 422)
3932
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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