A High Resolution Gravimetric Geoid of the Eastern Africa Region

Evaluation of the Recent High-Degree Combined Global Gravity-Field Models for Geoid Modelling Over Kenya

“…It is important to note that the entire geoid model over Kenya is below the reference ellipsoid (GRS80) for a proper interpretation. A comparison between EIGEN-6C4-based gravimetric geoid model and the geoid model of the Eastern Africa region (Gachari & Olliver, 1998) would reveal more about the potential of the current GGMs in geoid modelling over Kenya. However, the Eastern Africa geoid model data was not available for the current study.…”

“…This accuracy was achieved after removing the biases in the differences between Doppler/levelling and gravimetric geoid undulations. The accuracy of Doppler data was ±1 ~ ±3 m while levelling data was obtained by trigonometric heighting (Gachari & Olliver, 1998), indicating a lack of accurate data for validating a gravimetric geoid model over Kenya in 1998.…”

“…All the four models have not been evaluated in Kenya, except EGM2008 but only in Nairobi area (Odera, 2016). Recent evaluations of these models in other parts of the world can be found in Kostelecký et al (2015) (EGM2008 and EIGEN-6C4), Gilardoni et al (2016) (EGM2008, EIGEN-6C4 and GECO), and Liang et al (2018) (EGM2008 and SGG-UGM-1).Geoid modelling over Kenya has been done mainly by low and medium resolution global gravity-field models, GEM10B~upto degree-36 (Gachari & Olliver, 1986) and OSU91A~up to degree-360 (Gachari & Olliver, 1998). The most recent geoid model over Kenya, covering Eastern African region (Gachari & Olliver, 1998) was developed using OSU91A (Rapp et al, 1991) as a reference geopotential model, combined with terrestrial gravity and satellite altimetry data by applying remove-compute-restore procedure (Gachari & Olliver, 1998).…”

“…Geoid modelling over Kenya has been done mainly by low and medium resolution global gravity-field models, GEM10B~upto degree-36 (Gachari & Olliver, 1986) and OSU91A~up to degree-360 (Gachari & Olliver, 1998). The most recent geoid model over Kenya, covering Eastern African region (Gachari & Olliver, 1998) was developed using OSU91A (Rapp et al, 1991) as a reference geopotential model, combined with terrestrial gravity and satellite altimetry data by applying remove-compute-restore procedure (Gachari & Olliver, 1998). An accuracy of this geoid UDC 528.21…”

A Preliminary Geoid Model for Africa

“…Africa has always lagged behind other continents in terms of geodetic research, and the quest for a precise geoid model is no exception. Although much work has been done on developing geoid models for Africa (Obenson 1985;Merry and van Gysen 1987;Gachari and Olliver 1998;Fashir et al 1998;Benahmed Daho and Kahlouche 2000;Amod and Merry 2002a), these models cannot be said to be either precise or complete. More recently, a collaboration between African geodesists initiated by the Committee for Developing Countries of the International Association of Geodesy has led to a project for the computation of the geoid in Africathe African Geoid Project (Merry and Blitzkow 2001).…”