The high-resolution gravimetric geoid of Morocco: MORGEO

Abstract

In spite of the difficulty to obtain data for the African continent, the necessary measurements for the determination of a high-resolution geoid for Morocco have been collected. In Morocco, since the publication of most recent geoid (MGG97) a new geopotential model is available (EIGEN-CG01C, released on October 29, 2004) and a new high-resolution digital terrain model (SRTM 90M obtained from the Shuttle Radar Topography Mission), has been developed for the whole earth. Logically, these new data represent improvements that must be included in a new geoid for Morocco. For this reason, a new gravimetric geoid determination has been carried out including these new data. The method used in the computation of the geoid has been the Stokes integral in convolution form, because it is an efficient method to reach the proposal objective. The terrain correction has been applied to the gridded gravity anomalies, to obtain the corresponding reduced anomalies. The indirect effect has been also taken to account. Thus, a new geoid is provided as grid data distributed for Morocco from 27° to 37° of latitude and −14° to 0° of longitude (extending 10 × 14°), on a 401 × 561 regular grid with a mesh size of 1.5′ × 1.5′ and 224961 points in the GRS80 reference system. This calculated geoid and previous geoids existing for this study area (MGG97 and EIGEN-CG01C), are compared to the geoid undulations corresponding to 6 GPS/levelling points on Morocco. The new geoid shows an improvement in precision and reliability, fitting the geoidal heights of these GPS/levelling points with more accuracy than the other previous geoids.