The Accuracy of Gravimetric Deflections of the Vertical as Derived from the Gem 7 Potential Coefficients and Terrestrial Gravity Data.

Abstract

Abstract : The deflections of the vertical can be determined with a combined method using point gravity anomalies, mean anomalies and satellite spherical harmonics in the inner-, intermediate- and remote zones, respectively. In essential, the error sources of the intermediate and distant zone are studied. The RMS error contribution of the remote zone was found considerably dependent on the distance of truncation. Another dominating error source is the error due to lack of more detailed gravity data than 1 x 1 deg mean anomalies in the intermediate zone. Smaller block sizes are recommended between the distances 1 and 10 deg from the point of computation. A significant gain of accuracy will be achieved in the total error by extending the radius of truncation of at least 30 deg. Anticipating an inner zone error of 1.8 sec (a solution by collocation) the total RMS error will hardly be less than 2.2 sec, while for an inner zone error of 0.4 sec, the total error might decrease to 1.3 sec. (Author)