Geoid for Africa

Within the African geoid project of the International Association of Geodesy (IAG), Prof. Abd-Elmotaal (Minia/Egypt) and Prof. Kühtreiber (Graz/Austria) are working together on the further development of a precise geoid model for Africa.

The available data set of severity values has significant data gaps. These data gaps are filled with the EIGEN-6C4 model on a 15' x 15' grid. The window-remove-restore technique is used to generate the reduced severity anomalies with minimal variance to minimize interpolation errors, especially with these large data gaps.

The global model EIGEN-6C4, complete to degree and order 2190, is used as a reference model. Based on these reduced anomalies of varying accuracy, a 5' x 5' grid based on a least squares solution is predicted.

The reduced gridded gravity anomalies are then used to calculate the geoidundulation using the Stokes' integral with the modified Meissl core function to better combine the different wavelengths of the earth's gravity field. The gravimetric geoid obtained in the final restore step is scaled using the satellite model DIR_R5 GOCE.

The current geoid model is the AFR-geo2019.