World geodetic system 1984-a summary of enhancements through the development of the new geopotential model EGM96

Abstract

Summary form only given, substantially as follows. EGM96 is a geopotential model of the Earth consisting of spherical harmonic coefficients complete to degree and order 360. This model is the result of a collaboration between the National Imagery and Mapping Agency, the NASA Goddard Space Flight Center and the Ohio State University, supported by the Naval Surface Warfare Center. The joint project took advantage of new surface gravity data from many different regions of the globe, including data newly released from the NIMA archives. Major terrestrial gravity acquisitions by NIMA since 1990 include airborne gravity surveys over Greenland and parts of the Arctic and the Antarctic, surveyed by the Naval Research Laboratory, and cooperative gravity collection projects, several which were undertaken with the University of Leeds. These collection efforts improved data holdings over many of the world's land areas, including Africa, Canada, parts of South America and Africa, Southeast Asia, Eastern Europe, and the former Soviet Union. EGM96 also included altimeter derived anomalies derived from the U.S. Navy's GEOSAT geodetic mission and from ERS-1 over portions of the Arctic and Antarctic, as well as the altimeter derived anomalies over the Weddell Sea. Other data that contributed to EGM96 were direct satellite altimetry from TOPEX/POSEIDON, ERS-1 and GEOSAT, and satellite tracking to over 20 satellites using satellite laser ranging (SLR), the Global Positioning System, DORIS, Tracking and Data Relay Satellite System, and TRANET. In addition, a new topographic data base was assembled from all available sources in order to reduce raw surface gravity data and prepare the 30'/spl times/30' gravity anomalies. This database was also used to calculate isostatic values in the roughly 3 percent of the globe where surface gravity data was not available. This new geopotential model is being used as a geodetic reference to update WGS 84. In addition, it will serve as a state of the art model for precise orbit, oceanographic, and geophysical studies. The paper will summarize the results of the EGM96 development.