These grid files were used to produce gravity and basin depth maps of the Basin and Range Province, western United States. The maps show gravity values and modeled basin depths in this area. The data were compiled by the U.S. Geological Survey, Denver, Colorado. This data base was received in June, 1995. For further information see the readme.txt file in this directory(data\grids\basinrng), and the "Gravity and Basin-Depth Maps of the Basin and Range Province, Western United States", by R.W. Saltus and R.C. Jachens, Map GP-1012.

These grid files were used to produce gravity and basin depth maps of the Basin and Range Province, western United States. The maps show gravity values and modeled basin depths in this area. The data were compiled by the U.S. Geological Survey, Denver, Colorado. This data base was received in June, 1995. For further information see the readme.txt file in this directory(data\grids\basinrng), and the "Gravity and Basin-Depth Maps of the Basin and Range Province, Western United States", by R.W. Saltus and R.C. Jachens, Map GP-1012.

These grid files were used to produce gravity and basin depth maps of the Basin and Range Province, western United States. The maps show gravity values and modeled basin depths in this area. The data were compiled by the U.S. Geological Survey, Denver, Colorado. This data base was received in June, 1995. For further information see the readme.txt file in this directory(data\grids\basinrng), and the "Gravity and Basin-Depth Maps of the Basin and Range Province, Western United States", by R.W. Saltus and R.C. Jachens, Map GP-1012.

A 2.5 kilometer Bouguer anomaly grid for the state of Utah. Number of columns is 196 and number of rows is 245. The order of the data is from the lower left to the right and then up one row.

A 2 kilometer Bouguer anomaly grid for the state of Maine. Number of columns is 197 and number of rows is 292. The order of the data is from the lower left to the right and then up one row.

A 2 kilometer Bouguer anomaly grid for the state of Ohio. Number of columns is 187 and number of rows is 217. The order of the data is from the lower left to the right and then up one row.

A 2 kilometer Bouguer anomaly grid for the state of Nevada. Number of columns is 282 and number of rows is 397. The order of the data is from the lower left to the right and then up one row.

isotop.bin - topographic data for conterminous U.S. projected on an 8 km grid. Projection is Albers, central meridian = 96 degrees West, base latitude = 0 degrees North. Elevations are in meters.

isores.bin - standard grid containing isostatic residual gravity map for U.S. Grid interval = 4 km. Projection is Albers (central meridian = 96 degrees West; base latitude = 0 degrees North). Sea level depth of compensation = 30.0 km, density contrast at depth = 0.35 g/cm^^3. Values are in milligals.

This 2' geoid height grid for the conterminous United States is the GEOID96 model. The computation used about 1.8 million terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). By means of a Fast Fourier Transform (FFT) technique, high frequency corrections were made to an underlying EGM96 geopotential model through a remove, compute, and restore process. 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. GEOID96 incorporates the reference system relationship between NAD 83(86) and ITRF94(1996.0), the datum offset of NAVD 88, and the contributions from 2951 GPS on leveled benchmarks. Additional information is available at http://www.ngs.noaa.gov/GEOID/geoid.htmlWe are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.