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Directory Title: U.S. Terrain Corrected Free Air Anomalies (96)
Principal Investigator: Dr. Dennis G. Milbert

Contributing Organization: NOAA, National Geodetic Survey, N/NGS5
1315 East-West Highway, Room 9349
Silver Spring, MD 20910-3282

Summary: This 2' gravity anomaly grid for the conterminous United States is NOT the input data set used in development of the GEOID96 model. This gravity grid models the 1.7 million terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. The data used in this grid have NOT been augmented by gravity data contributions from NIMA (former Defense Mapping Agency). Please note that the GEOID96 model itself does contain the NIMA contributions. These gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). Terrain corrected, atmospherically corrected, Bouguer anomalies were computed with respect to the Geodetic Reference System 1980 (GRS80) using NAD83 and NAVD88 coordinates. Terrain corrections were computed by FFT integration of 30” digital elevation data throughout the United States. These complete Bouguer anomalies were gridded by splines in tension. The free air anomaly grid was obtained by restoring the Bouguer plate with a 2' mean elevation grid.

Additional information is available at: http://www.ngs.noaa.gov/GEOID/

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