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Directory Title: Mexico Terrain Corrected Free Air Anomalies (97)
Principal Investigator: Dr. Dru A. Smith

Contributing Organization: NOAA, National Geodetic Survey, N/NGS5
1315 East-West Highway, Room 9316
Silver Spring, MD 20910

Summary: This 2' gravity anomaly grid for Mexico, North-Central America and the Western Caribbean Sea is NOT the input data set used in the development of the MEXICO97 model. This gravity grid represents one million gravity measurements held in the NGS gravity database as of March 1997. The data used in this grid have NOT been augmented by gravity data contributions from NIMA, but have been augmented by 2'x2' satellite-altimeter-derived gravity anomalies computed by Sandwell and Smith (1997). Please note that the MEXICO97 geoid model does contain the NIMA contributions. Large data gaps south of 20 degrees North latitude were filled with 15'x15' gravity values derived from the EGM96 global geopotential model. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). The geoid heights are referred to the Geodetic Reference System 1980 (GRS80) ellipsoid, centered at the origin of the International Terrestrial Reference Frame 1994 (ITRF94(1996.0)).

Additional information is available at: http://www.ngs.noaa.gov/GEOID/MEXICO97/

As an aid to the user, an ASCII map of the western portion of the data coverage for this free air gravity anomaly grid (not the grid for MEXICO97) is given below:

This is an ASCII map of file:
mex97.nosyn.ns9.released.b
It is bounded in latitude by: 14.0 to 33.0 N(degrees) and in longitude by: 241.0 to 274.0 E(degrees)
Cell sizes mapped are 30.0 minutes in lat and 30.0 minutes in lon
For a cell to have an X, instead of a space, it must contain a minimum of 13.0 points
and a maximum of 999999.0 points.
There are a total of 38 cells in latitude and 66 cells in longitude.

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