Performance Evaluation of the Earth Gravitational Model 2008 (EGM2008) - A Case Study

Abstract

Ghana’s local geodetic reference network when pick data with the GPS is being reference to the World Geodetic System 1984, with data in latitude, longitude and ellipsoidal height. This prevalent situation makes it possible to apply the New Earth Gravitational model to determine the geoidal height at each GPS point with the geographic coordinates. Researchers have therefore proposed various methods of determining the geoidal undulations for a local and national geodetic networks and improving the recent New Earth Gravitational model accuracies and its performances. This project therefore seeks to evaluate such method of improving the recent New Earth Gravitational model in a part of the University of Mines and Technology, UMaT, Tarkwa. The geoid heights implied by the model are compared with 328 discrete geometrical heights from co-located GPS and Total station orthometric heights of the University Primary Levelling Networks. The methods applied were the EGM2008 model, a geometric method and a polynomial mathematical model for improving the recent geoid model. The statistics of the differences between GPS/levelling derived geoid heights and corresponding geoid heights obtained from the geoid model suggests that, the EGM2008 model is most suitable at this moment. The RMS, Mean, and the Standard deviation of their geoidal height differences are 0.120825 m, 2.18823 m, and 3.47678 m, which is  better in the area of interest. The study concluded that, the recent geoid model can be applied in UMaT and the polynomial mathematical model is the best model for modelling EGM2008 for a local geoid model.