About GAMIT

GAMIT and GLOBK are a comprehensive suite of programs developed by MIT, Scripps Institution of Oceanography, and Harvard University for analyzing GPS measurements primarily to study crustal deformation, generating orbit/EOP products, and establishing and maintaining the reference frame. The GAMIT home page is available.

The SOPAC data archive GAMIT directory contains all of the setup files listed here.

Global list

Regional list

The International Terrestrial Reference Frame is defined by IERS and is updated every few years. The most recent reference frame is ITRF2014. The previous two frames were ITRF2005 and ITRF2008.

Based on ITRF 2014, IGS created a frame specific for GNSS technology, known as IGS14.

The derivation of ITRF is based on multiple modern space geodetic techniques, namely GNSS, SLR, VLBI, and DORIS.

The current SOPAC data analysis, since January 1, 1995  (GPS week 0782), is based on the IGS14 reference frame. IGS14 is derived from the analysis of GNSS only solutions contributed by IGS Data Analysis Centers while the core stations are constrained onto ITRF2014 defined stations. Therefore, its positions/velocities are completely consistent with IGS published orbits/clocks and earth orientation parameters (EOP), as well as all the physical models and model corrections, such as the antenna phase center model for receivers and satellites, the differential code biases (DCB), and various tidal loading displacements etc. SOPAC routinely processes a large volume of GPS data (about 3000 sites) collected from both global and regional networks.

The a priori coordinates used in SOPAC data processing come from three sources:

1. IGS14 definition (major offsets caused by large earthquakes are considered);
2. SOPAC multi-year solutions (if velocities are estimated);
3. Most recent SOPAC weekly solutions (if velocities have not been estimated or affected by earthquakes).

The true of date a priori files containing the above mentioned a priori coordinates are date sensitive. They are updated weekly and are available as aprioriFile_YYYY_DOY.txt.