GPS Data - Institut Geographique National (IGN), IGS Global Data Center, France

The International GPS Service for Geodynamics (IGS) supports researchers who use satellites in the U.S. Defense Department's Global Positioning System (GPS) for studies in geodynamics. GPS satellites transmit signals that allow one to determine, with great accuracy, the locations of GPS receivers. The receivers can be fixed on the Earth, in moving vehicles, aircraft, or in low-Earth orbiting satellites. The time evolution of receiver locations allows researchers to study the motions of tectonic plates, displacements associated with earthquakes, earth orientation, and other geophysically interesting phenomena. Global Positioning System (GPS) uses microwave measurements of range (transmitter-to-receiver distance), accurate to within a centimeter or less, to determine positions of stations on the Earth's surface. Relative site positions can be measured to within a centimeter. This system was developed by the U.S. Department of Defense for military navigation and timing. The INTERNATIONAL GPS SERVICE FOR GEODYNAMICS (IGS), a service established by the International Association of Geodesy (IAG), officially started its activities on January 1, 1994, after a successful pilot phase of more than one year. IGS is based on about 40 globally distributed permanent GPS tracking sites, three Global Data Centers, five Operational or Regional Data Centers, seven Analysis Centers, and a Central Bureau. Some fifty institutions and organizations contribute to these activities. IGS routinely provides : -High-quality orbits for all GPS satellites (estimated accuracy better than 20 cm). -Earth Rotation Parameters -Contributions to the determination of the tracking site coordinates in the International Terrestrial Reference Frame (ITRF), in cooperation with the International Earth Rotation Service (IERS). -Phase and pseudorange observations in daily RINEX files for each IGS tracking site. Institut Geographique National (IGN), France, is a Global Data Center of IGS. It is accessible by FTP at "ftp://igs.ensg.ign.fr/pub/igs/products/". The following data is available from the IGN Data Center : Data is kept available on-line for 150 days. Access may be made available to off-line data on special request. The data would be on 9-inch tape, optical disk, or exabyte tape. Questions may be directed to the IGS Central Bureau as well as to this data center.