Assessment of the latest generation GOCE-based global gravity field models using height and free-air gravity anomalies over South Africa

Abstract

The latest Gravity field and steady-state Ocean Circulation Explorer (GOCE) global gravity field models (GGMs) are evaluated over South Africa using 118 GPS/levelling, 507 gravity and 88,968 SAGEOID10 data points. It is observed that GOCE data can improve quasi-geoid model in the long-to-medium wavelength components over South Africa. GOCE-based GGMs perform better than EGM2008 in recovering height anomalies up to 240°. Related results are obtained for free-air gravity anomalies, but the improvement over EGM2008 by GOCE data is only up to 180°. TIM5 (up to 240°) is selected as a candidate GOCE model and combined with EGM2008 (from 241 up to 2190°). This model (TIM5/EGM2008) is evaluated by observed data (GPS/levelling and gravity) and the latest hybrid quasi geoid model over South Africa (SAGEOID10). The solutions converge at 1200 and 1800° for height and free-air gravity anomalies, respectively, when TIM5/EGM2008 is used. Results show that TIM5/EGM2008 can effectively recover height and free-air gravity anomalies over South Africa. The standard deviations of the differences between observed (118 GPS/levelling and 507 gravity points) and TIM5/EGM2008 implied height and free-air gravity anomalies are ± 23.7 cm and ± 9.0 mGal, respectively. In addition, the standard deviation of the differences between SAGEOID10 and TIM5/EGM2008 implied height anomalies (at 88,968 grid points) is ± 21.7 cm. The results for height anomalies from TIM5/EGM2008 are comparable with the latest gravimetric quasi-geoid model over South Africa.