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Abstract

The gravitational potential of the earth has been presented in a spherical harmonic series that is complete to degree and order 250. This solution has been obtained by first carrying out a combination of satellite derived potential coefficients (GEML2') with a set of 1 deg by 1 deg mean free air anomalies. These anomalies were formed from a merger of a June 1986 terrestrial set and a set derived from Geos-3/Sesat altimeter data. The combination solution was carried out after making downward continuation corrections to the surface anomalies and ellipsoidal corrections to the a priori potential coefficients. The adjustment yielded 582 potential coefficients and 64800 1 deg by 1 deg anomalies. Two combination solutions were made, one (OSU86C) that excluded geophysically predicted anomalies and one (OSU86D) that included 5547 such anomalies. The potential coefficients are determined through an optimal estimation procedure where, primarily, sampling error was minimized. Tests of the new solution were made by comparing undulation residuals at Doppler stations, and by using the field, up to degree 36, in orbit calculations. In North American the root mean square undulation difference was + or - 1.55 m. The undulation residuals are found to correlated with elevation although it is not clear why.