NAME
presort3d - compute sort tables for 3D data sets
SYNOPSIS
presort3d [ -Nntap ] [ ... ] [ -Nntap ] [ -Ootap ] [
-Hw1TrWrd1 ] [ -Hw2TrWrd2 ] [ -Hw3TrWrd3 ] [ -Hw4TrWrd4 ] [
-Hw5TrWrd5 ] [ -Hw6TrWrd6 ] [ -Hw7TrWrd7 ] [ -M ] [ -offoff
] [ -grpgrp ] [ -R ] [ -X ] [ -K ] [ -V ] [ -? ]
DESCRIPTION
presort3d computes the common source, common receiver, com-
mon depth (DI), common line (LI), and common offset sort
table, or alternately, five arbitrary primary sorts from
user specified trace header words plus one secondary and one
tertiary sort. The header words are specified by mnemonic
(see scan documentation for list of header mnemonics and
their descriptions). Header words may still be referred to
by their old SIS 1/2 word position although users are urged
to discontinue this practice.
Another use is to build sort tables for the 2D case where
lines are very long and exceed the UNIX file size limit
(~2Gb) or have to be distributed over multiple file systems.
In this application sisort3d must also be used to read the
table and do the actual sorting. These sort tables cannot be
read by sisort, the regular 2D sorting routine.
The sort table has the following entries:
LINE 1 - Secondary sort word mnemonic, Tertiary sort word
mnemonic
LINE 2 - total number traces to be sorted, number of
receiver + source components
LINE 3 - five triplets (number gathers, number
traces/gather, max traces within tertiary sort) for common
receiver, common shot, common depth (DI), common line (LI),
and common offset sorts
LINE 4 - first receiver index, receiver index increment
LINE 5,6,... first 5 numbers are the sorted primary indices
(receiver, shot, depth, line, and offset); the next 5 pairs
of numbers are the corresponding sequential record and trace
locations for the primary indices
It is always prudent to check to see you have reasonable
numbers in LINE 3. If you haven't then it is an indicator
that the input data have bad indices for some of the sort
types.
The user should decide beforehand the general sorting stra-
tegy, i.e. does the data come down the pipeline in LI/DI
[inline sort] order (all DI's for line 1, all DI's for line
2, etc) or in DI/LI [crossline] order (all LI's for first
DI, all LI's for second DI, etc). In the first case the
user can go with the default secondary sort header word
mnemonic (DphInd - DI); in the second case the user will
have to specify LinInd as the secondary sort word mnemonic.
presort3d gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
and verbose printout, if desired.
Note: the data must have been preperly prepped prior to
running presort3d (it is highly recommended that you use
pr3d as the prep program. The indices that absolutley must
be correct are the DI's and LI's. If pr3d has been run
these are integer pointers to the cells of the X-Y grid over
the survey and will be correct. If these indices are not
correct and you can't re-prep the line then bite the bullet
and use ufh the put the correct DI & LI's into the traces.
Note: if you sort the input data and at some point in the
preocessing the sorted data are output onto disk you must
run presort3d again to create a new table if you plan to
re-sort these data. The act of physically sorting changes
the layout on disk so the old roadmap is no longer valid.
Once the forward and backward sort tables have been built
presort3d does not have to be run again unless the geometry
again changes for some reason on disk (e.g. the ranges are
limited and the results written to disk)
WARNING: the table produced by presort and presort3d are
different and so these table can not be interchanged with
the respective sort programs sisort and sisort3d.
Command line arguments
-N ntap
Enter the input data set name(s) or file(s) immediately
after typing -N. If the data lie on several disk parti-
tions then the names should be input using repeated
-N[] command line arguments in the order in which the
data partitions were filled up, i.e. you must not for
instance have the last partition of the 3D line as the
first -N[]; it must be the last -N[].
-O otap
Enter the output data set name or file (i.e. sort table
name) immediately after typing -O. The output data set
also requires the full path name (see above).
-Hw1 TrWrd1
Enter the first trace header word mnemonic to sort on
(one of three). Default = RecInd (receiver index).
-Hw2 TrWrd2
Enter the second trace header word mnemonic to sort on
(two of three). Default = SrcLoc (source index (source
point x10)).
-Hw3 TrWrd3
Enter the third trace header word mnemonic to sort on
(three of three). Default = DphInd (depth index).
-Hw4 TrWrd4
Enter the fourth trace header word mnemonic to sort on.
Default = LinInd (line index).
-Hw5 TrWrd5
Enter the fifth trace header word mnemonic to sort on.
Default = DstSgn (signed trace distance).
-Hw6 TrWrd6
Enter the secondary trace header word mnemonic to sort
on. Default = DphInd (DI number).
-Hw7 TrWrd7
Enter the tertiary trace header word mnemonic to sort
on. Default = DstSgn (signed trace distance).
-M Enter the command line argument '-M' to sort on binned
trace distances. These are derived from the command
line arguments below. Note: this will not change the
actual trace distances on disk
-off off
Enter the absolute maximum offset found in the data
(ft,m). If this is not known try running scan with a
-S (for summary) on the command line. This will tell
you the max & min offsets for each record.
-grp grp
Enter the group interval (ft,m). This is used with the
offset above to derive a model spread for binning the
distances.
-R Enter the command line argument '-R' to round the trace
distances to the nearest 10 units (ft, m) before sort-
ing
-X Enter the command line argument '-X' to retain original
record numbers in the sort table. This option should
be used only if one wishes to eyeball the sort table to
see where the traces will go upon execution of sisort
and is not intended for normal processing
-K Enter the command line argument '-K' to retain dead
traces in the sort table. This takes up more space but
the table is now an exact roadmap of the data on disk.
NOTE: with this option the dead traces must have all
the correct header indices. If they do not you are in
big trouble.
-V Enter the command line argument '-V' to get additional
printout. Even if this is not set the printout file
will contain useful information regarding the sort
indices and the number of live traces associated with
each, and also the minimum and maximum X and Y coordi-
nates for source, receiver, midpoint, and depth points
in the data set (the latter XY info also comes out of
sr3d1). Also the minimum and maximum trace distances
are printed out.
-? Enter the command line argument '-?' to get online
help. The program terminates after the help screen is
printed.
EXAMPLE 1
To build a sort table with LI's as the secondary sort
indices:
presort3d -Nindata -Osort_table -Hw6LinInd
When this is run you could for example stream the data off
disk in DI primary order (DI changing slowest), LI secondary
order, and offset ordered within LI's by entering
sisort3d -Nindata -Osorted_data -nsort_table -D
EXAMPLE 2
To build a sort table with DI's as the secondary sort
indices:
presort3d -Nindata -Osort_table
When this is run you could for example stream the data off
disk in LI primary order (LI changing slowest), DI secondary
order, and offset ordered within DI's by entering
sisort3d -Nindata -Osorted_data -nsort_table -L
To build a sort table on a very long 2D data set that
requires 2 disk partitions:
presort3d -Nindata1 -Nindata2 -Hw4DphInd -nsort_table
Then, to do the sort on this data:
sisort3d -Nindata1 -Nindata2 -nsort_table -L
So, for vey long 2D lines the input data does not have to be
contiguous on disk.
There of course many other combinations but the above two
are probably the main ones of use to most users.
SEE ALSO
sisort3d
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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