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G A M I T
R
eference Manual
GPS Analysis at MIT
Release 10.3
T. A. Herring, R. W. King, S. C. McClusky
Department of Earth, Atmospheric, and Planetary Sciences
Massachussetts Institute of Technology
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Table of Contents
1. File Structure and Naming Conventions........................................................................ 4
1.1 Introduction.............................................................................................................. 4
1.2 Site-occupation-specific files................................................................................... 4
1.3 Experiment or session-specific files ........................................................................ 7
1.4 Global files............................................................................................................. 15
1.5 Summary of files.................................................................................................... 18
2. Creating Data Input Files............................................................................................. 21
2.1 Introduction and file organization.......................................................................... 21
2.2 Preparing the coordinate (L-) file .......................................................................... 22
2.3 Creating the station information file...................................................................... 24
2.4 Creating a scenario file .......................................................................................... 27
2.5 Using makexp......................................................................................................... 28
2.6 Creating G- and T-files from external ephemerides.............................................. 29
2.7 Creating satellite clock (J-) files............................................................................ 32
2.8 Running makex....................................................................................................... 34
2.9 Description of the X-file........................................................................................ 38
2.10 Creating station clock (K- and I-) files................................................................ 39
3. Batch Processing.......................................................................................................... 42
3.1 Introduction............................................................................................................ 42
3.2 Running fixdrv ....................................................................................................... 43
3.3 Executing the batch run ......................................................................................... 57
3.4 Evaluation the solutions......................................................................................... 64
4. Data Editing................................................................................................................. 78
4.1 Introduction............................................................................................................ 78
4.2 Automatic editing using autcln.............................................................................. 79
4.3 Scanning the residuals to identify slips.................................................................. 88
4.4 Interactive editing using cview .............................................................................. 92
4.5 Strategies for editing............................................................................................ 102
5. Running the Modules Individually ............................................................................ 106
5.1 Introduction.......................................................................................................... 106
5.2 Running arc ......................................................................................................... 106
5.3 Running model..................................................................................................... 110
5.4 Running cfmrg ..................................................................................................... 113
5.5 Running solve ...................................................................................................... 114
5.6 Running autcln..................................................................................................... 118
6. Automatic Batch Procesing ....................................................................................... 136
6.1 Overview.............................................................................................................. 136
6.2 Control files ......................................................................................................... 138
6.3 Using sh_gamit ..................................................................................................... 140
6.4 Using sh_glred ...................................................................................................... 143
7 Atmospheric Delay Models ........................................................................................ 147
7.1 Description of the atmospheric delay .................................................................. 147
7.2 Algorithms for the propagation delay.................................................................. 148
7.3 Estimating zenith delay paramaters..................................................................... 149
7.4 Estimating gradients ............................................................................................ 151
7.5 Extracting estimates of precipitable water........................................................... 152
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8. Utility Programs and Auxiliary Tables...................................................................... 153
8.1 Plotting and computing statistics from GAMIT solutions................................... 153
8.2 Creating RINEX or FICA files from NGS ARGOS files.................................... 157
8.3 Creating RINEX files form FICA files................................................................ 158
8.4 Creating X-files from C-files............................................................................... 159
8.5 Creating RINEX files from X-files...................................................................... 159
8.6 Creating and maintaining datum, time, spacecraft, and ephemeris tables........... 159
Appendices...................................................................................................................... 165
A.1. Antenna Specifications .......................................................................................... 165
A.1.1. Introduction..................................................................................................... 165
A.1.2. TI 4100 antennas............................................................................................. 165
A.1.3 Trimble antennas.............................................................................................. 166
A.1.4 Rogue antennas ............................................................................................... 167
A.1.5 Ashtech antennas ............................................................................................. 168
A.1.6 Macrometer antennas....................................................................................... 170
A.1.7 SERCEL antennas............................................................................................ 170
A.1.8 Leica antennas.................................................................................................. 170
A.2. Description of Data Exchange Formats................................................................. 172
A.2.1 RINEX ............................................................................................................. 172
A.2.2 FICA................................................................................................................. 172
A.2.3 Navigation files................................................................................................ 172
A.2.2 SP3 orbit file .................................................................................................... 175
A.3 Modeling Satellite Clock Variations due to SA...................................................... 177
References....................................................................................................................... 180
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1. File Structure and Naming Conventions
1.1 Introduction
All the program modules adhere to specific conventions for the naming of files for a
particular experiment. This assures a unique definition of each experiment, facilitates
data file management, and allows for ease of interactive processing and troubleshooting.
There are four types of files:
1) site-occupation-specific
2) session- or survey-specific
3) global
Each file is distinguished either by its first character (types 1 and 2) or a unique name
(type 3). Type 1 files are named using 4-character station codes and the day number of
the observations. Type 2 files have a 4-character experiment (survey) or solution name,
chosen by the analyst and usually the day number. Type 3 files have specific names that
are hard-wired in the software (though these names are often elaborated using links).
These naming conventions allow the software to perform the bookkeeping necessary to
process large quantities of data.
The next three sections describe the contents and format of the files of each type, and
how the file is created and used by the software. Section 1.5 has an alphabetical list of all
files and a chart showing what files are read and written by each GAMIT module.
1.2 Site-occupation-specific files
RINEX obs file : Observation data file containing the L1 and L2 carrier beat phases and
pseudo-ranges, signal amplitudes, initial station coordinates and
antenna offsets, start and stop times, and the identification of the
satellites tracked in each receiver channel.
Name :
sitedayn.yyo
Example :
vndn0020.87o. Date from station VNDN (Vandenberg0 on day 2 of
1987.
Type : ASCII
Created by : Programs written by manufacturers, AIUB, or UNAVCO (
teqc) to read
raw (binary) files downloaded from receivers.
Input to : makex and optionally cview
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RINEX met file : Meteorological data collected at the station.
Name : sitedayn.yym
Example :
vndn0020.87m. Data from station VNDN (Vandenberg on day 2 of
1987.
Type : ASCII
Created by : Programs to read raw (binary) files downloaded from met sensors.
Input to : model and
sh_met_util
X-file : GAMIT observation file, similar to the RINEX file except that the
files for all stations used in a session start and stop at the same time
(with empty epochs where observations were not obtained
Name :
xsitey.day
Example :
xvndn7.002. Data for VNDN from day 2 of 1987.
Type : ASCII
Created by : makex and optionally utility ctox
Input to : makek and fixdrv; optionally bctot and cview
C-file : Primary file for data analysis, created by model from an X-file and
used as input to autcln, cview, and solve; contains observations (O's),
prefit residuals (O-C's, observed-computed values), partial derivatives,
and auxiliary information.
Name :
csitey.day
Example :
cvndn7.002
Notes : Direct correspondence to X-files but binary and with partials. If cycle
slips needed to be repaired manually with cview, ctox may be used to
convert the cleaned c-files to x-files for further process, though this is
now rare.
Type : Binary
Output of : model, autcln, cview
Input to : autcln, scandd, cview, solve
K-file : Receiver clock data computed by makex or makek using nominal site
coordinates, broadcast ephemeris, and pseudo-range. It is used by
fixdrv to estimate the coefficients of a linear or cubic polynomial
model for clock behavior during the session.
Name :
ksitey.day
Example :
kvndn7.002
Notes : The parameters and format of the station-specific K-file are described
in Section 2.9.
Type : ASCII
Output of : makex, makek
Input to : fixdrv and utilities calck and plotk .
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