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CoverNewton's Bulletin

Issue n. 5, June 2015 - Assessment of GOCE Geopotential Models    [pp. 37-48]

Validation of GOCE Gravity Field Models in Germany

C. Voigt, H. Denker

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The fifth release of global gravity field models (GGMs) from the GOCE mission published in mid-2014 are based on observation data from the whole mission lifetime. High precision gravity field data sets in Germany are utilized to validate the GOCE GGMs of the fourth and fifth release processed by the time-wise (TIM) and the direct approach (DIR) as well as their internal uncertainty estimates. The comparisons are performed between EGM2008 and the GOCE GGMs up to spherical harmonic degree and order (d/o) 200 in terms of quasigeoid heights, gravity anomalies and vertical deflections. For the comparisons of GPS/levelling data and astrogeodetic vertical deflections with the GOCE GGMs, the different spectral characteristics of the data sets are considered by modelling the high frequency signals above d/o 200 by EGM2008 and detailed topographic information within the residual terrain model (RTM) approach. The RMS differences of all comparisons are introduced as observations within a least squares adjustment in order to estimate the commission errors of the GOCE GGMs as well as the uncertainties from all other terms involved in the comparisons, i.e. EGM2008, RTM effects and GPS/levelling. The commission errors of the fifth release GOCE GGMs up to d/o 200 are estimated to 2.5 cm and 2.4 cm for TIM5 and DIR5, respectively, as well as 0.66 mGal and 0.10? for both models in terms of quasigeoid heights, gravity anomalies and vertical deflections, respectively. This is in good agreement with the formal error degree variances of TIM5, while for DIR5 a factor of 3 is proposed. Moreover, both fifth release GOCE GGMs show significant improvements of approx. 30% compared to their predecessors.