Abstract
Geoid modelling is a fundamental procedure in geomatics and geosciences applications to estimate the orthometric heights from the ellipsoidal heights measured using Global Navigation Satellite Systems (GNSS) observations. In case of no local geoid model is available for any area, a Global Geopotential Model (GGM) is utilized for height conversion. However; the availability of too many GGMs, more than 160 models, makes the selection of the most acceptable one is a significant task. This paper aims to develop a straightforward scheme to acquire, manipulate, and investigate the accuracy of GGMs, within a Geographic Information Systems (GIS) environment. Four GGMs, namely XGM2016, GECO, EIGEN-6C4, and EGM2008, have been utilized in Egypt. Accomplished results show that the standard deviations of the investigated GGMs' discrepancies, over Egypt, range from ± 10.90 mGal to ± 13.10 mGal for gravity anomalies, and from ± 0.23 m to ± 0.30 m for geoid heights. In order to pick up the optimum GGM, a dimensionless reliability index is computed for each GGM. Based on the investigated GGMs, the available datasets, and also the proposed criteria applied in analyzingresults in this paper, we can conclude that the EGM2008 is still the most suitable GGM for representing the gravitational field over Egypt with an average reliability index of 5.10. The proposed efficient GIS-based process is practically beneficial for height conversion in several geodetic, environmental, surveying, and mapping applications in Egypt.
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