Scholarly record

REGIONAL ANALYSIS OF RECENT GLOBAL GEOPOTENTIAL MODELS: A CASE STUDY IN TURKEY

Selda Demir, Assoc. of Prof. Dr. Ramazan Alpay Abbak

Abstract

Geoid is an equipotential surface of EarthпїЅs gravity field, which partially coincides with the mean sea level and extended inside continents. In the gravimetric geoid determination; global geopotential models (GGMs), digital elevation models and terrestrial gravity observations are combined in a proposed technique (e.g. Remove-Compute-Restore). The external Earth's gravity field is represented by a GGM that consists of the globally and homogeneously distributed terrestrial and satellite gravity measurements. Currently, CHAMP, GRACE, and GOCE satellite missions have been used to determine the gravity field. Satellite-based GGMs that mainly represent the long wavelength components of the gravity field can be evaluated externally by using terrestrial data such as ground gravity, GPS-leveling, etc. Then, the standard deviation of the differences (e.g. NGGM minus NGPS-LEV) is considered as the accuracy of the model. In this study, geoid undulations derived from recently published GGMs are compared with equivalents obtained from GPS-leveling data, and the accuracies of selected GGMs are investigated in the territory of Turkey. Numerical results show that GGMs combining GRACE and GOCE data are more accurate than the others.

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