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Evaluation of EGM2008 and latest GOCE-based satellite only global gravity field models using densified gravity network: a case study in south-western Turkey

M. Simav and H. Yildiz

Abstract: 

Gravity standardisation network of Turkey is being renewed and densified within the "Turkish Height System Modernisation" project. 2190 new relative gravity sites at about 10-km spatial resolution and 16 new absolute gravity sites are established and measured with A10 absolute and Scintrex CG-5 relative gravimeters in the south-western Turkey. The densified network is adjusted based on the weighted constrained least squares method using the gravity observations reduced for environmental and instrumental effects, resulting with a mean formal error of 17 μGal. The gravity disturbances from this highly precise network are used as a reference data set to evaluate the four latest GOCE-based satellite-only models in the same region by spectral enhancement method minimising the omission errors in GOCE models using EGM2008 and ERTM2160 gravity models. Results show improvements in the spectral bands ˜120 to ˜190 in terms of spherical harmonic degrees for all GOCE-based models compared to EGM2008. Of all the GOCE models assessed, GOCE-DIR5 is found to be best extending the improvement to degree ˜220. Furthermore, it is found that GOCE models detect significant bias in EGM2008 reaching up to 5 mGal which is verified by regional comparisons of GOCE-based models and EGM2008 with TR-GravNet ground truth data.