Run GAMIT for three days in 2018

In the test_install/2018/ directory type

$ sh_setup -yr 2018
What did this command do?

You should notice that a tables/ sub-directory was created, which contains copies of several critical files, most generic but some specific to the year, from the main ~/gg/tables/ directory. You may wish to edit some of these files to suit your needs to process your experiment. Take a look at what was generated, e.g. ls -l tables/.

The 2018/tables/ directory will now contain links to most standard files in ~/gg/tables/ and copies of these files for process.defaults, sestbl., station.info (complete MIT version), and autcln.cmd. The sites.defaults file was written for this test (ordinarily one would construct this station list) and already in the directory, and therefore not overwritten by sh_setup.

Examine tables/sites.defaults to note that it has been set up to download from a remote archive (CDDIS by default) RINEX files for ten IGS stations and xstinfo is set to avoid any automatic update of station.info during processing. Note also that the sittbl. copied from ~/gg/tables/ is set up to impose moderate constraints on IGS core stations to support ambiguity resolution in GAMIT; the four included in test_install are more than sufficient.

Edit tables/process.defaults to change the mailto to your own email address to receive the sh_gamit summary file. (If left null, it reverts to whoami, so this change may not be needed.) Note that aprf, used to initialize the lfile. for GAMIT points to igb14_comb.apr, which has been copied by sh_setup to the 2018/tables/ directory.

If you have not downloaded or copied from an earlier distribution the (large) grid file for ocean tidal loading and do not wish to use it, change Tides applied in tables/sestbl. from 31 to 23.

Construct a small, experiment-specific station.info file by using the following procedure in the 2018/tables/ directory:

$ sh_upd_stnfo -l sd

will create station.info.new, using from the MIT station.info only the sites listed in sites.defaults. (This step will take a while since the MIT global station.info file is so long.) After checking, rename it to station.info (overwriting the no-longer-useful MIT station.info). (In your own processing, if you have stations that are not in the MIT station.info file, you can add their entries from the RINEX headers by running in tables/

$ sh_upd_stnfo -files ../rinex/*.18o

(See Section 3.4 of Introduction to GAMIT/GLOBK for what to do if the RINEX header entries are non-standard.)

GAMIT currently supports processing of each GNSS separately, with the day directories for each created with a single-letter added to designate the system, e.g. 095G/, 095R/, 095E/, 095C/. If you wish to test full GNSS capability, type at the 2018/ level

$ sh_gamit -expt eura -gnss G -s 2018 095 097 -pres ELEV -orbit igsf -copt x k p -dopts c ao >& sh_gamit_2018G.log
sh_gamit -expt eura -gnss R -s 2018 095 097 -jclock sp3 -pres ELEV -orbit codm -copt x k p -dopts c ao >& sh_gamit_2018R.log
sh_gamit -expt eura -gnss E -s 2018 095 097 -pres ELEV -orbit codm -copt x k p -dopts c ao >& sh_gamit_2018E.log
sh_gamit -expt eura -gnss C -lfreq 7 -s 2018 095 097 -pres ELEV -orbit codm -copt x k p -dopts c ao >& sh_gamit_2018C.log

For GPS-only, execute only the first command and omit the -gnss so that the day directory names will be the day-of-year only.

A summary file should be emailed to you as each day completes execution. Check these files for number of stations (6), postfit RMS (3–15 mm, none 0), postfit NRMS (~ 0.2), ambiguity resolution and coordinate adjustments (< 30 cm). For this large network, the 2018 ambiguity resolution is 80–90% for GPS and Galileo, 40–50% for Beidou, but near zero for GLONASS due to poor orbits), a condition also reflected in the sky plots in the figs/ directory. Allowing the GLONASS orbits to adjust (RELAX mode in the sestbl.) will improve the fit signficantly. To view the result of the fit of GAMIT’s orbit model to the input orbit, see the RMS files in igs/. To view the complete editing statistics see autcln.prefit.sum and autcln.post.sum in the day directories; for the least-squares adjustment, see qeuraa.<ddd>.

Optionally, remove the x, k, and p files from the day directories to save space:

$ sh_cleanup -d 2018 095 096 097 -dopts x k p

Notes:

  1. For large or complex data sets, the utility sh_get_times can be helpful in determining the days and session spans to be processed.

  2. In creating station.info for your own experiments, it is important to check it after updating from the RINEX headers unless you are sure these headers are correct. In processing, the station.info entries always override whatever is in the RINEX header or the x-files. An alternative way of creating entries for survey-mode sites is to use interactive program make_stnfo, then use sh_upd_stnfo to merge this file with the one created from the MIT station.info file for continuous sites. The survey-mode file will have a shorter form of the station.info format, but this will be converted when it is merged with the continuous file, which should be listed as the reference (-ref) in the call to sh_upd_stnfo.

  3. The example is set up to use ocean tidal loading (Use otl.grid = Y in the sestbl.), which requires you to have previously downloaded into ~/gg/GRIDS/ an OTL file from ftp://everest.mit.edu/pub/GRIDS/ and to have verify this file is linked to ~/gg/tables/otl.grid. The IERS/IGS standard model is otl_FES2004.grid (730 Mb). You may, however, substitute the smaller (45 Mb) otl_CSR4.grid, or you may turn off ocean tidal loading by setting Tides applied = 23 and Use otl.grid = N in the sestbl. (Note that the links to the other grid and list files (met.grid, met.list, map.grid, etc.) can remain empty for running the example and for most processing.

  4. If you want or need to run the example without having internet access while running, you can pre-load the RINEX, navigation, and orbit files into the rinex/, brdc/, and igs/ directories, respectively.