Gravity anomalies and sea surface heights have been computed on a 0.125 degree grid in the ocean areas from a combined GEOS3/SEASAT/GEOSAT altimeter data set. This data base was received in March 1993. The area of data coverage is latitude 72N to 72S and longitude 0E to 360E.

GEOSAT DATA: Gridded Gravity Anomalies for the Southern Ocean

GEOSAT DATA: Gridded Gravity Anomalies for the Southern Ocean

A detailed gravimetric geoid has been computed on a 10' by 10' grid for Canada by the University of New Brunswick. This data base was received in April 1989. Principal gravity parameters include latitude, east longitude, and total geoidial height above GRS'80 reference ellipsoid. The gravity data used for the spheroidal Stokes's integration consisted of point gravity anomalies for the innermost zone, of 5'x5' mean gravity anomalies for the inner zone, and 1x1 degree mean gravity anomalies for the outer zone.

The dgrav gridded data set was produced by NGDC by regridding the Decade of North American (DNAG) 6-km gravity grid of N. America. A grid cell dimension of 2.5 minutes of longitude and latitude was used in this regridding process. In order to facilitate the comparison of the various regridded data, a geodetic reference system was used as the most suitable common coordinate frame.

This 2' x 4' surface deflection of the vertical grid for Alaska is the DEFLEC96 model. The computation used about 1.1 millionterrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravitydata contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). The deflections were obtained by numerical differentiation of cubic spline models along the parallels of the GEOID96 grid.

This 2' x 4' surface deflection of the vertical grid for Alaska is the DEFLEC96 model. The computation used about 1.1 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 DefenseMapping Agency). The deflections were obtained by numerical differentiation of cubic spline models along the meridians of the GEOID96 grid.

This 2' x 4' geoid height grid for Alaska is distributed as a GEOID96 model. The computation used 1.1 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.

This 2' x 4' gravity anomaly grid for Alaska is NOT the input data set used in development of the GEOID96 model. This gravity grid models the 1.1 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.

This 2' x 4' gravity density grid for Alaska displays the distribution of about 1.1 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)) and by satellite altimeter-derived marine gravity anomalies computed by Sandwell and Smith (1996). The values show the number of gravity data contained in a given 2' x 4' cell.