3.1. Setup

The first step in running the scripts is to create a project directory (e.g. emed18/ or emed/2018/ for data from 2018 for the eastern Mediterranean) with two subdirectories: rinex/ and tables/.

Copy into the rinex/ directory all of the local RINEX files you plan to use in your processing. GAMIT will handle either RINEX 2 or RINEX 3 formats, but the RINEX 3 files must be renamed to the 10-character RINEX 2 naming scheme (lowercase <ssss><ddd><s>.<yy>o and brdc<ddd><s>.<yy>n; this happens automatically in sh_gamit). RINEX files for IGS directories to be downloaded automatically during the processing are specified using entries in a control file (sites.defaults) (see Section 3.3 and Section 6.3 of the GAMIT Reference Manual).

Then run sh_setup to link or copy into the project tables/ directory the appropriate control and data files. All of the required templates and tables reside in ~/gg/tables/, where ~/gg/ is a required alias pointing to the highest level of the GAMIT/GLOBK installation. Executing sh_setup will invoke sh_links.tables to link the standard data tables described in Section 3.2) and will copy the eight control and data files listed below:

process.defaults

Edit this file to specify your computation environment, sources for internal and external data and orbit files, start time and sampling interval, instructions for archiving the results, and an email address to receive a summary of the run.

sites.defaults

Edit this file to specify which local and IGS stations are to be used and how station meta-data are to be handled.

station.info

This file contains the receiver and antenna type and height of instrument (HI) values as a function of time for all occupations of the stations you will use. Although it can be generated during processing by sh_gamit, the best approach is usually to construct the file prior to processing using the tools described in Section 3.4.

Coordinate files

sh_gamit maintains in the experiment tables/ directory two files of a priori coordinates. The file ending in .apr (set as aprf = igb14_comb.apr in the current ~/gg/tables/process.defaults template) contains the Cartesian coordinates (position and velocity) of stations you wish to have unchanged throughout the processing. The L-file (lfile.), which can contain either Cartesian position and velocity (default, same as .apr file) or spherical position (GAMIT old-style, use the -oldfmt_lfile option in sh_setup), is updated after each day is processed if the adjustments exceed a specified value (0.3 m by default). If you have good coordinates for stations not in the .apr file, you should append these to the .apr file if you want them to be unchanged. For any station that does not have coordinates in lfile., sh_gamit will attempt to calculate coordinates via a pseudorange solution, or (if use_rxc = Y in process.defaults) use the coordinates in the RINEX header. When GAMIT runs, these coordinates will be updated in the project tables/lfile. from the phase solution so that for successive days on which the same station is observed, the accurate coordinates will be used.

sestbl. and sittbl.

Edit these files to set the appropriate options for your analysis. Make sure that any station for which you specify tight constraints in sittbl. has accurate coordinates in the .apr file.

autcln.cmd

Controls for cleaning the data in program autcln. This file will usually not require editing unless you encounter unusual data during the processing.