Vol. 58, No. 1, 2023
Abstract
An optimum Global Geopotential Model (GGM) is required either to represent the long wavelength of the Earth’s gravitational field in gravimetric geoid modelling or to act as a stand-alone national geoid in some developing countries. Thus, the current research aims to investigate the performance of seven recent high-order GGMs over Egypt utilizing the most recent precise Global Navigation Satellite Systems(GNSS)/Levelling datasets. Attained results showed that the investigated GGMs perform differently over Egypt with an accuracy level varying between ±0.249m for the SGG-UGM-1 model and ±0.300m for the GECO model. Removing outliers in the terrestrial dataset reveal significant improvements, in terms of standard deviations. Consequently, the performance of the investigated GGMs has been modified where the EIGEN-6C4 model became the best model with a standard deviation equals ±0.172m. Furthermore, a 3D spatial correction surface has been constructed and has been added to the original EIGEN-6C4 model to get an enhanced version of the global EIGEN-6C4. Over checkpoints, the average error of the enhanced model equals −0.018m with a standard deviation equal ±0.011m. That means that incorporating terrestrial geodetic data into the global EIGEN-6C4 model has increased its accuracy in Egypt by almost 36 %. Accordingly, such developed enhanced GGM represent the optimum stand-alone geoid model in Egypt. Nevertheless, such accuracy levels of GGMs do not fulfill the requirements of high-accuracy surveying and civil engineering applications. That concludes that a precise national geoid model is still crucial. It is recommended that all available geodetic datasets should be collected from all governmental and private organizations to construct a national geodetic database that would be implemented in modelling an Egyptian local geoid.