ROLI topographic gravity field model, from four-layer Earth decomposition

The determination of the global gravity field has gained momentum due to high accuracy satellite-derived observations and development of forward gravity modelling. Forward modelling computes the global gravitational field from mass distribution sources instead of actual gravity measurements and helps improving and complementing the medium to high frequency components of the global gravity field models. In this study, we approximate the global gravity potential of the Earth’s upper crust based on ellipsoidal approximation and a mass layer concept. Lateral density variations within a sequence of thin volumetric shells bounded by confocal lower and upper shell ellipsoids are used in the computation of the ellipsoidal harmonic coefficients which are then transformed into spherical harmonic coefficients on the Earth’s surface in the final step. The main outcome of this research is a spectral representation of the Earth’s upper crust’s gravitational potential, computed up to degree and order 3660 in terms spherical harmonic coefficients (ROLI_EllApprox_SphN_3660).