A computational scheme to model the geoid by the modified Stokes formula without gravity reductions

In a modern application of Stokes' formula for geoid determination, regional terrestrial gravity is combined with long-wavelength gravity information supplied by an Earth gravity model. Usually, several corrections must be added to gravity to be consistent with Stokes' formula. In contrast, here all such corrections are applied directly to the approximate geoid height determined from the surface gravity anomalies. In this way, a more efficient workload is obtained. As an example, in applications of the direct and first and second indirect topographic effects significant long-wavelength contributions must be considered, all of which are time consuming to compute. By adding all three effects to produce a combined geoid effect, these long-wavelength features largely cancel. The computational scheme, including two least squares modifications of Stokes' formula, is outlined, and the specific advantages of this technique, compared to traditional gravity reduction prior to Stokes' integration, are summarised in the conclusions and final remarks.