Geoid is an equipotential surface of earth’s gravity field, which partially coincides with the mean sea level. The external Earth’s gravity field is represented by Global Gravitational Model (GGM) that consists of globally and homogeneously distributed terrestrial and satellite gravity observations. GOCE is one of satellite missions have been used to determine the gravity field of the earth. It is mainly representing the long wavelength components of the gravity field which can be evaluated externally by using terrestrial data such as GPS leveling. 17 GOCE models are evaluated against EGM2008 and 134 GPS leveling stations. The RMSE of the undulation differences (N (GOCE models) – N (GPS leveling)) are considered as usual as a measure of the accuracy of the models. Another measure is used for evaluation, using the successive differences of the observed undulations against their corresponding values from the GOCE models. In this study, Different types of GOCE models with different degree and order are examined against observed undulations and EGM2008 at three different station spacing. About 5 km which is the approximate distance between every two successive data points, about 9 km which is the EGM2008 resolution, and finally about 85 km which is the average resolution of the assessed GOCE models. Numerical results showed that some of GOCE models gave comparable results with EGM2008 especially at level of undulation differences. |
