1. Preface

GAMIT/GLOBK is a comprehensive GNSS analysis package developed at MIT, the Harvard-Smithsonian Center for Astrophysics (CfA), Scripps Institution of Oceanography (SIO), and Australian National University (ANU) for estimating station coordinates and velocities, stochastic or functional representations of post-seismic deformation, atmospheric delays, satellite orbits, and Earth orientation parameters. Although the software is currently maintained by the four authors of this document at MIT and ANU, many people have made substantial contributions. The orbital integration and modules used in computing the theoretical phase observable have their origins in the Planetary Ephemeris Program (PEP) written by Michael Ash, Irwin Shapiro, and Bill Smith at Lincoln Laboratory in the 1960s, with later contributions by Bob Reasenberg and John Chandler at MIT. The codes for processing GPS observations were developed at MIT in the 1980s by Chuck Counselman, Sergei Gourevitch, Yehuda Bock, Rick Abbot, and King. GAMIT attained its current form through the efforts of Bock, Danan Dong, Peng Fang (SIO), Kurt Feigl, Herring, King, McClusky (ANU), Mike Moore (ANU), Peter Morgan (Canberra U), Mark Murray (NM Tech), Liz Petrie (U Newcastle), Berkhard Schraffin (Ohio State), Seiichi Shimada (NEID), Paul Tregoning (ANU), and Chris Watson (U Hobart). GLOBK was developed by Herring and Jim Davis at CfA for combination of VLBI data and modified at MIT to incorporate GPS data. Details of these contributions may be found in the references listed at the end of this manual. Funding for the early development of GAMIT was provided by the Air Force Geophysics Laboratory, and for GLOBK by NASA. Current support for development and support of the scientific community comes primarily from the National Science Foundation.

To control processing the software uses shell scripts (stored in com/ and mostly named to begin with sh_) which invoke the Fortran or C programs compiled in the libraries/, gamit/, and kf/ directories. The software is designed to run under any UNIX operating system supporting X-Windows, including LINUX and MacOS. The parameter logic allows a maximum of 99 sites and the standard distribution is dimensioned for 80 sites, but since the run is proportional to the cube of the number of parameters, with networks larger than 50 sites greater efficiency is obtained by parallel processing using connected subnets. IGS processing at MIT includes over 300 sites, and processing at New Mexico Tech for the North American Plate Boundary Observatory over 1000 sites.

The first chapter of this manual provides some theoretical background for readers not familiar with high-precision GNSS analysis. Chapter 2 describes the setup of tables and commands for automatic processing to obtain time series of daily position estimates, and Chapter 3 provides a guide to evaluating your results. In Chapter 4 we discuss various approaches to generating time series and estimating station velocities from observations spanning several years. More detailed documentation is available in the longer GAMIT Reference Manual and GLOBK Reference Manual. There are also tutorials available on-line at http://geoweb.mit.edu/gg/. The most up-to-date information about the commands is available through help files, invoked by typing the name of the shell-script or program without arguments.