Some geophysical and geodetic contributions of satellite-determined gravity results

Satellite orbital data yield reliable values of low degree and order coefficients in the spherical harmonic expansion of the Earth's gravity field. The second degree coefficient yields the shape of the Earth — probably the most important single parameter in geodesy. It is crucial in the numerical evaluation of different forms of the theoretical gravity formula. The new information requires the standardization of gravity anomalies obtained from satellite gravity and terrestrial gravity data in the context of three most commonly used reference figures, e.g.,International Reference Ellipsoid, Reference Ellipsoid 1967, andEquilibrium Reference Ellipsoid. This standardization is important in the comparison and combination of satellite gravity and gravimetric data as well as the integration of surface gravity data, collected with different objectives, in a single reference system.Examination of the nature of satellite gravity anomalies aids in the geophysical and geodetic interpretation of these anomalies in terms of the tectonic features of the Earth and the structure of the Earth's crust and mantle. Satellite results also make it possible to compute the Potsdam correction and Earth's equatorial radius from the satellite-determined geopotential. They enable the decomposition of the total observed gravity anomaly into components of geophysical interest. They also make it possible to study the temporal variations of the geogravity field. In addition, satellite results make significant contributions in the prediction of gravity in unsurveyed areas, as well as in providing a check on marine gravity profiles.On leave from University of Hawaii, Honolulu.