| U.S. Terrain Corrected Free Air Anomalies (96) |
| 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 NGA (former National Imagery and Mapping Agency (former Defence
Mapping Agency)). Please note that the GEOID96 model itself does contain the NGA (former
National Imagery and Mapping Agency) 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/geoid.html |
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