Abstract: . The gravity field is important to determine the size and shape of the earth, to determine the heights, to investigate the structure of the crust, and to explore the mineral wealth. A lot of gravity observations have been taken in Egypt. Those gravity observations are taken over a long-time span with different gravimeters, different references, and different processing methodologies. Those huge amounts of data need to be filtered and unified before using them in precise geoid determination. In the advent of satellite missions for gravity field determination and the yielded global gravity models with good resolution and precision, filtering the terrestrial observed gravity and improving the global gravity models should be done. In this research, the recent Global Geopotential Models (GGMs) will be used in filtering the terrestrial gravity anomalies, and then the reliable terrestrial anomalies will be used in improving the global model gravity anomalies. Four recent GGMs (EGM2008, XGM2019e_2159, GOCO06s, and SGG-UGM 2) are validated using terrestrial gravity anomalies to determine which model best fits the Earth’s external gravity field in Egypt. Thousands of terrestrial gravity anomalies are collected as different data sets, so one of the aims of this research is to unify them using the common points among them. Finally, gravity anomalies are used to obtain their corresponding undulation values using a simple model. The obtained results of this study are recommended when collecting all the gravity observations taken all over Egypt to compute precise gravimetric geoid |
