Two different views of topographical and downward-continuation correctionsin the Stokes-Helmert approach to geoid computation

Two different methods to handle the topographical and downward-continuation corrections in Stokes' formula are investigated. The first approach is to correct observed gravity anomalies for the the effect of topographic masses , then downward-continue the corrected gravity anomaly to the geoid using P oisson's integral. After Stokes' formula has been applied, the gravitationa l effects of the masses on the geoid are restored using the indirect primar y effect. The second approach is to add all topographic effects as a total correction to the original Stokes formula, which includes a new method to e stimate the effect of downward continuation. These two methods are compared at 23 global positioning system (GPS)-levelling stations in Sweden. The re sults of this comparison show that both methods work well, with the first m ethod having better agreement with the GPS-levelling geoid. The standard de viation of fit in the first method is computed to be +/-1.1 cm, while it is +/-2.1 rm for the second method after a four-parameter fit.