Menu entry LocSAT
Interface to the location program of Steve Bratt and Walter
Nagy. This program is not part of the distribution of SH/SHM.
It must be copied and installed separately. The code is a mixture
of Fortran and C. For some platforms executable version are available
on our ftp server.
Calling this entry writes all phases which are picked and have
a quality factor (see phase dialog box)
of at least 2 (!) into a scratch file which is passed to LocSAT
and run. The output of LocSAT is displayed in a text window and
the location results also read into SHM. If the location program
does not work, please check first the quality factor of your phases.
The dialog box of LocSAT has the following options:
- Depth: If
the value is set to free
the location algorithm inverts also for depth. This can cause
instabilities. Fixing it to a value sometimes improves the location,
if the depth can be guessed. But fixing to a completely wrong
value also makes the inversion instable (and makes the location
bad).
- Auto start loc:
A value of yes
causes LocSAT to compute a starting location by itself,
no means LocSAT takes
the closest station as the starting location.
- Table prefix:
Prefix of the travel time tables used for the inversion. The
tables are located in $SH_LOCSAT/tables
(LocSAT does not use the travel time tables of SH/SHM). The tables
with the prefix tab
are created with the IASP91 velocity model. Provide your own
tables with another prefix, then you may switch between the tables.
- Deg. of freedom:
Degrees of freedom. I don't really know ...
- Max iterations:
Maximum number of iterations. After this number of iterations
the location algorithm is stopped, it does not converge, at least
not fast enough.
- Brief output:
Tells whether the output file of LocSAT should be shown as original
(no, rather lengthy)
or should be reduced to the most important results (yes).
Installation of the LocSAT tar file has to be done in
$SH_UTIL:
cd $SH_UTIL; tar xvf <locsat-tarfile>
A man page of LocSAT itself is then found in
$SH_UTIL/locsat/doc/man/man1.
To read it enter in a C-shell:
setenv MANPATH ${MANPATH}:$SH_UTIL/locsat/doc/man
man LocSAT
For debugging: what happens is:
- SHM writes three files in $SH_SCRATCH:
locsat_c.txt
with control information, locsat_s.txt
with station information and locsat_d.txt
with phase readings.
- It calls the command (in $SH_SCRATCH):
$SH_UTIL/LocSAT
-c locsat_c.txt -s locsat_s.txt -d locsat_d.txt -o locsat_r.txt
which creates the output file
locsat_r.txt. All these files remain
on $SH_SCRATCH
until they are overwritten by the next call to LocSAT. There
they may be examined to find any errors in processing.
- The output file locsat_r.txt
is reformatted to locsat_edit.txt
if not switched off in the LocSAT dialog box (option
brief output).
- locsat_edit.txt
or (locsat_r.txt)
is displayed on screen and the location results put to the analysis parameter box.
Please note a bug in LocSAT: if the path to the travel time
table files (given as $SH_LOCSAT
in $SH_ROOT/setup/shsetup)
is too long (more than 22 characters) the program crashes. If
your path is longer then you have to use a link to your LocSAT
tables directory which is shorter and 22 characters. This link
you have to specify in the definition of $SH_LOCSAT in
$SH_ROOT/setup/shsetup. Do not change
the definition of $SH_LOCSAT_EXEC.
This page last modified 13-Jul-2000