GOCE Data for Local Geoid Enhancement

The GOCE gradients, having a spatially dense data distribution, may potentially provide better predictions of the regional gravity field than those obtained using a spherical harmonic Earth Geopotential Model. The aim of this study is to develop a methodologyto improve the use of GOCE gradients and to determine the Earth’s gravity field with better accuracy than by using global models, which have been truncated at a specific harmonicdegree and order. The method makes use of all available GOCE gradient data in addition to the global models and aims at improving the determination of Earth’s gravitational field in regional areas. Subsequently, the calculated geoid is used together with measurements of sea surface height in a calculation of the Mean Dynamic Topography.In regional geoid recovery from GOCE gradients, two methods are used, one of them being Least-Squares Collocation (LSC). The second method is developed as a part of this study, and it is based on the Reduced Point Mass (RPM) response. The results show that the RPM method and LSC method give very similar results when using the same data, i.e.the difference is insignificant when compared to the EGM2008 results. However, when all of the available GOCE gradient data are used with the RPM method, an improvement inthe gravitational field determination is achieved. The enhanced geoid by the RPM methodis then used for the improvement of the MDT in the North Atlantic region.