Optimum Combinations of GGM and GDEM Models for Precise National Geoid Modelling


  • Essam Mohamed Al-Karargy Department of physical geodesy, Survey Research Institute, National Water Research Center, Cairo, Egypt
  • Gomaa Mohamed Dawod Department of physical geodesy, Survey Research Institute, National Water Research Center, Cairo, Egypt




GGM, DEM, GNSS, geoid, Egypt


This study aims to develop a Local Geoid Model (LGM) for Egypt to determine the optimal combinations of global models with Global Navigation Satellite Systems (GNSS/Levelling) data. A precise national geodetic dataset, four Global Geopotential Models (GGMs), and three global Digital Elevation Models (DEMs) have been utilized. Hence, twelve gravimetric LGMs have been developed using the Least-Square Collocation (LSC) method fitted to GNSS/Levelling data and judged over 100 checkpoints. Results revealed that improvements in local geoid accuracy are attributed mainly to GGMs models representing the long wavelength of the Earth's gravitational field. Regarding DEMs, the accuracy of LGMs does not significantly depend on the utilized DEM. Based on the available data, the attained optimum geoid of Egypt has been developed with a standard deviation, equals 0.129 m.


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How to Cite

Essam Mohamed Al-Karargy and Gomaa Mohamed Dawod, “Optimum Combinations of GGM and GDEM Models for Precise National Geoid Modelling”, Proc. eng. technol. innov., vol. 18, pp. 15–24, Feb. 2021.