Evaluation of recent Global Geopotential Models over South Africa

Abstract

This study evaluates the performance of three recent global geopotential models (GGMs)—WHU-SWPU-GOGR2022S, GOSG02S, and Tongji-GMMG2021S—over South Africa by comparing both height anomalies and free-air gravity anomalies derived from these models to data from 141 GPS/Levelling points and 105,408 gravity data stations, respectively. The comparison method is crucial as it directly relates the model outputs to precise geodetic measurements, providing a clear picture of model accuracy and effectiveness. Specifically, the Tongji model, developed using GOCE data, exhibited the smallest bias (3.9 cm) with a standard deviation of ±31.7 cm, demonstrating the most accurate fit among the evaluated models. Additionally, the free-air gravity anomalies comparison yielded biases of -1.74 mGal, -1.69 mGal, and -1.74 mGal for the WHU, Tongji, and GOSG02S models, respectively, with corresponding standard deviations around ±19 mGal. These comparisons not only validate the models against the established South African quasigeoid model, CDSM09A, but also highlight areas for potential refinement. The method employed enhances the study's contribution to transitioning to a geoid-based vertical datum, improving the accuracy of height and gravity measurements across South Africa, and underlining the utility of these models in regional geophysical applications.