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Directory Identifier: GRAVCD-egm96
Directory Title: EGM96: The NASA GSFC and NIMA Joint Earth Geopotential Model
Principal Investigator: Numerous
Contributing Organization:F. G. Lemoine, and D. E. Smith
Laboratory for Terrestrial Physics
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771 U.S.A.
email: flemoine@olympus.gsfc.nasa.gov
email: dsmith@tharsis.gsfc.nasa.gov

Summary:

EGM96 is a geopotential model of the Earth consisting of spherical harmonic 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; and (3) the quadrature solution at degree 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.

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 of 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'x30' mean altimeter derived gravity anomalies from the GEOSAT Geodetic Mission. EGM96 also included altimeter derived anomalies derived from ERS-1 by Kort and 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. The statistics of the final merged set of surface gravity data used in EGM96 are summarized in a table described at the URL noted above.

Other data that contributed to EGM96 are 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 (GPS), DORIS, Tracking and Data Relay Satellite System (TDRSS), and TRANET. In addition, as part of this effort a new topographic database was assembled from all available sources in order to reduce the raw surface gravity data, and prepare the 30' x 30' gravity anomalies. This database was also used to calculate the isostatic fill-in values in the roughly 3 percent of the globe where surface gravity data was not available. The geographical extent and availability of data is a major improvement over the surface gravity data available for OSU91A.

This new geopotential model will be 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.

Principal Authors and Collaborating Institutions

F. G. Lemoine, and D. E. Smith
Laboratory for Terrestrial Physics
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771 U.S.A.
email: flemoine@olympus.gsfc.nasa.gov
email: dsmith@tharsis.gsfc.nasa.gov

R. Smith and L. Kunz
National Imagery and Mapping Agency
Bethesda, Maryland 20816
email: kunzl@nima.mil

N. K. Pavlis, S. M. Klosko, D. S. Chinn, M. H. Torrence,
R. G. Williamson, C. M. Cox, K. E. Rachlin, and Y. M. Wang
Hughes-STX Corporation
Greenbelt, Maryland 20770 U.S.A.
email: npavlis@geodesy2.gsfc.nasa.gov
email: sklosko@magus.stx.com

E. C. Pavlis
Laboratory for Terrestrial Physics
NASA Goddard Space Flight Center &
Department of Astronomy, University of Maryland
College Park, Maryland 20742 U.S.A.
email: epavlis@helmert.gsfc.nasa.gov

S. C. Kenyon, R. Salman, and R. Trimmer
National Imagery and Mapping Agency
St. Louis, Missouri 63118 U.S.A.
email: kenyons@nima.mil

R. H. Rapp
Department of Civil and Environmental Engineering and Geodetic Science
The Ohio State University
Columbus, Ohio 43210 U.S.A.
email: rhrapp@ohstmvsa.acs.ohio-state.edu

R. S. Nerem
Center for Space Research
The University of Texas at Austin
Austin, Texas 78712 U.S.A.
email: nerem@csr.utexas.edu

NOTE: Additional information is available here. Please see also the description for EGM96: The NASA GSFC and NIMA Joint Geopotential Model at URL: http://cddisa.gsfc.nasa.gov/926/egm96/egm96.html

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