NASA’s Crustal Dynamics Data Information System (CDDIS) provides an archive of regional experiment data, previously funded by NASA and international cooperative programs. Starting in 1990, studies in the geophysical integrity of NASA's Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) sites were undertaken utilizing Global Positioning System (GPS). Small networks of GPS sites were selected in an approximate 10-20 km radius around the main observing monuments at several of key sites. The measurements taken at these "footprint" sites allow analysts to estimate the local tectonic stability of the area they encompass, assuring the integrity of the space geodetic measurements taken at these critical sites. In addition to the surrounding footprint sites, measurements are taken at the reference monuments placed at a distance of 50 to 100 meters to the main marker. GPS measurements at the reference monuments allow analysts to continue to monitor the physical stability of the main observing monuments and provide additional data for the estimation of the regional tectonic stability of the area.

Summary of CDDIS GNSS Experiment Data Holdings

• Spatial and temporal coverage information (see table below)
• Data Volume: ~50 Mbytes/experiment
• Data Format: Typically Receiver INdependent EXchange (RINEX) format; some raw receiver data also available