EGM96 is a geopotential model of the Earth consisting of spherical harmonic
Spherical Harmonic
Spherical Harmonic is a science fiction novel from the Saga of the Skolian Empire by Catherine Asaro. It tells the story of Dyhianna Selei , the Ruby Pharaoh of the Skolian Imperialate, as she strives to reform her government and reunite her family in the aftermath of a devastating interstellar...

 coefficients complete to degree and order 360. It is a composite solution, consisting of:
  1. a combination solution to degree and order 70,
  2. a block diagonal solution from degree 71 to 359,
  3. and the quadrature solution at degree 360.

This model is the result of a collaboration between the National Imagery and Mapping Agency (NIMA), the NASA Goddard Space Flight Center (GSFC), and Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...


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 Lab (NRL) and cooperative gravity collection projects, several which were undertaken with the University of Leeds. These collection efforts have improved the 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. In addition, there have been major efforts to improve NIMA's existing 30' mean anomaly database through contributions over various countries in Asia.

NIMA also computed and made available 30'×30' mean altimeter derived gravity anomalies from the GEOSAT
The GEOSAT was a U.S. Navy Earth observation satellite, launched on March 12, 1985 into an 800 km, 108° inclination orbit, with an orbital period of 23.07 days and a 330 pass orbit. The satellite carried a radar altimeter capable of measuring the distance from the satellite to sea surface...

 Geodetic Mission. EGM96 also included altimeter derived anomalies derived from ERS-1
European Remote-Sensing Satellite
European remote sensing satellite was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun-synchronous polar orbit at a height of 782–785 km.-Instruments:...

 by Kort & Matrikelstyrelsen (KMS), (National Survey and Cadastre, Denmark) over portions of the Arctic, and the Antarctic, as well as the altimeter derived anomalies of Schoene [1996] over the Weddell Sea.

PGM2000A is an EGM96 derivative model that incorporates normal equations for the dynamic ocean topography implied by the POCM4B ocean circulation model.

The official Earth Gravitational Model EGM2008 has been publicly released by the National Geospatial-Intelligence Agency (NGA) EGM Development Team. This gravitational model is complete to spherical harmonic degree and order 2159, and contains additional coefficients extending to degree 2190 and order 2159.

External links

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