An approach for improving the accuracy of global geopotential models over a local region: a case study in the Nile Delta, Egypt

Abstract

Adding local, precise geodetic datasets is necessary to improve the accuracy and performance of Global Geopotential Models (GGMs). Consequently, GGMs could be utilized in geosciences, geodetic, and geomatics applications, particularly in developing countries where no accurate geoid model is affordable. Typically, the discrepancies of geoid undulations at Global Navigation Satellite Systems (GNSS)/Levelling stations are utilized to establish a correction surface within a Geographic Information Systems (GIS) environment. The current research proposes a new approach that depends on taking into account both GGM errors in geoidal undulations and free-air gravity anomalies over a particular local region. This method has been carried out in the Nile Delta region, north of Egypt, utilizing 160 GNSS/Levelling stations and 20 terrestrial gravity points. Two GGM models have been investigated as candidates for high-resolution global models, namely the EGM 2008 and the SGG-UGM-2 models. The accomplished results showed that the traditional approach enhances the EGM2008 by 21% while the proposed weighted approach yields 45% improvements. Less enhancement has been reported for the SGG-UGM-2 model. The proposed approach does not require more local datasets and consequently no more economic costs are needed. Moreover, the processing methodology of that approach is quite straightforward, which means that it could be performed in other developing countries to enhance the performance of GGMs.