AFRgeo_v1.0: A Geoid Model for Africa

The paper presents an attempt to compute a geoid model for Africa in the framework of the IAG African Geoid Project. The available gravity data set consists of land point gravity data as well as shipborne and altimetry-derived gravity anomaly data, having a lot of significant gaps allover the continent. The reduced gravity anomalies are gridded on a 50´ x 50´ grid using an iterative process employing a tailored reference model, to fill in the data gaps, and a weighted least-squares prediction technique. The tailored reference model, up to degree and order 2160, has been used to compute a geoid model for Africa within the window remove-restore technique employing the Stokes integral in frequency domain by the 1-D FFT technique. For the sake of comparison, another geoid model for Africa has been computed using a different approach. This approach renounces the use of the topographic-isostatic reduction and uses the recent global combined geopotential model EIGEN-6C4, complete to degree and order 2190, serving as the reference model. The computed geoids are scaled using the GO_CONS_GCF_2_DIR_R5 GOCE satellite-only model, which represents the best available global geopotential model approximating the African gravity field. An extensive comparison between the geoids computed within the current investigation and the former geoid model for Africa has been carried out.