Validation of GOCE gravity field models using GPS-leveling data and EGM08: a case study in Brazil

Abstract

Validation of geopotential models derived from Gravity field and steady-state Ocean Circulation Explorer (GOCE) observations is a challenging task in regions with less advanced geodetic infrastructure such as Brazil. In order to assess the current performance of these models, 262 GPS-leveling sites, Earth Gravitational Model 2008 (EGM08) and Residual Terrain Model (RTM) are employed. The validation is based on the differences between GPS-leveling and GOCE-derived models. For the former, the spectral content beyond the GOCE-derived models’ maximum degree is removed by using EGM08 and RTM. The results indicate that the GOCE-based models: DGM-1S, SPW (Releases 1 and 2), TIM (Releases 1, 2, 3 and 4), and DIR (Releases 2, 3 and 4), at their maximum degrees have a worse performance than EGM08 while DIR-R1 shows an improvement of 11%. Furthermore, from the steepness of the slopes of the root mean square error (RMSE), it is observed that the optimal combination between DIR-R1 and EGM08 occurs at degree 230 (RMSE of 0.201 m). For the satellite-only models, DIR-R3 reduces the RMSE by ~1.4% compared to TIM-R4 at degree 190. These results are important for Brazil where the accuracy of the current geoid model is approximately 0.28 m.