Global gravity field modeling based on GOCE and complementary gravity data

• First high resolution gravity model which is independent from EGM08 has been derived.
• For the solution of the normal equation system 2 TB of working memory are required.
• We apply full covariance propagation from input data to the gravity field model.
• The validation of the model is performed by independent data sets.

A combined high-resolution global gravity field model up to degree/order (d/o) 720, including error estimates in terms of a full variance–covariance matrix, is determined from GOCE (Gravity field and steady-state Ocean Circulation Explorer) and complementary gravity field data. GOCE observations, highly accurate in the low to medium wavelength part (∼d/o 40–220), are supplemented by GRACE (Gravity Recovery and Climate Experiment) with high accuracy in the low wavelength part (∼d/o 2–150), and altimetric and terrestrial gravity field observations to enhance the spectral resolution of the combined gravity field model. The theory of combining different data sets by least-squares techniques, applying optimum weighting strategies, is illustrated. Full normal equation systems are used to enable stochastic modeling of all individual observations. High performance computing techniques are applied in order to handle normal equations of enormous size (about 2 TB). The quality of the resulting gravity field solution is analyzed by comparisons with independent gravity field models and GPS/leveling observations, and also in the frame of the computation of a mean dynamic topography. The validation shows that the new combined model TUM2013C achieves the quality level of established high-resolution models. Compared to EGM2008, the improvements due to the inclusion of GOCE are clearly visible.