GIS-based development of a unique terrestrial gravity database toward the redefinition of the national geoid of Egypt

Abstract The determination of a precise geoid model still represents a chief demand for the geodetic communities worldwide. It necessitates the collection of as much as terrestrial gravity measurements with a homogenous distribution over a spatial region. The current research aims to collect several gravity datasets from several organizations and to unify their geodetic datums and gravity references. Such a task has been carried out within a geographic information systems (GIS) framework. A number of 9724 terrestrial gravity stations have been analyzed to construct a unique integrated gravimetric database of Egypt. That database has been referenced to the World Geodetic System 1984 (WGS84) and has been related to the Egyptian National Gravity Standardization Network 1997 (ENGSN-97) framework. GIS analysis tools have been performed to determine common points between gravity datasets and to construct correction surfaces to relate each category to the ENGSN-97 reference. Accordingly, an enhanced free-air gravity anomaly dataset has been developed. Such a modified gravimetric dataset is slightly more precise than the original one and performs a little better when compared to a global gravitational model (GGM). It has been found that the unification process performed herein has slightly enhanced the gravitational field of Egypt by almost 6.6%. Furthermore, comparing the terrestrial gravity data against the global GGM model shows that an improvement of 3.1% has been attained in terms of standard deviation. On another scene, the proposed approach might be valuable to the undergoing project for developing a precise geoid model of Egypt where different datasets have been collected from different sources with large variations with respect to geodetic datums and gravity references.