Evaluation of EGM96 and EGM08 based on GPS/Levelling Heights in Egypt

Abstract

The heights determined by  Global Positioning System (GPS) refer to the ellipsoid called the World Geodetic System 1984 (WGS84).  Global Geopotential Models (GGMs) that are available on GNSS commercial software are generally used to transform  ellipsoidal heights to orthometric heights. In this study, the geoid heights of GPS/Levelling were computed to evaluate the accuracy of the geoid heights obtained from two GGMs, namely, the Earth Gravitational Model 96 (EGM96) and the Earth Gravitational Model 08 (EGM08). Seventeen (17) GPS/Levelling stations of the High Accuracy Reference Network (HARN) over Egypt were used for this purpose. The standard deviations for the differences between the geoid heights obtained through GPS/Levelling and those obtained from EGM96 and EGM08 were determined as  ± 1.212 m and ± 0.543 m, respectively. This research confirms that the geoid heights obtained from EGM08 are closer to the geoid heights determined using GPS/Levelling over Egypt.