On Combination of Heterogeneous Gravitational Observables for Earth’s Gravity Field Modelling

Abstract

The Earth’s gravitational field is described in geodesy by the geopotential, a scalar function of position and time. Although it is not directly observable, its functionals such as first- and second-order directional derivatives can be measured by ground, airborne or spaceborne sensors. In geodesy, these observables are usually used for recovery of the geopotential at some known simple reference surface. Since no observation technique providing gravitational data is fully ideal, ground, airborne and spaceborne data collected with different accuracies, spectral contents, temporal and spatial distributions must be combined. An observation model for recovery of the geopotential is based on the Abel–Poisson equation modified to various gravitational observables. Integral kernels weight spatially contributions of particular observables as functions of their position. Models for different observables are combined exploring stochastic and design characteristics of actual observations.