Assessment of EGM2008 using GPS/levelling and free-air gravity anomalies over Nairobi County and its environs

Patroba Achola Odera

Abstract


The performance of Earth Gravitational Model 2008 (EGM2008) is evaluated over Nairobi County and its environs using GPS/levelling and free-air gravity anomalies. The data used include 18 GPS/levelling and 97 gravity points. The heights in Kenya are referred to the mean sea level and they are generally considered as orthometric heights. Hence the height anomalies obtained from tide-free EGM2008 model are converted to geoid undulations using a conversion model supplied with EGM2008. The standard deviation of the differences between EGM2008 implied and GPS/levelling geoid undulations at the 18 points is ±11.6 cm while the standard deviation of the differences between EGM2008 implied free-air and observed free-air gravity anomalies at the 97 points is ±10.7 mGal. These results indicate a high potential for EGM2008 in geoid modelling over Kenya. An initial high-resolution gravimetric geoid model over Kenya can be developed by combining EGM2008 and local gravity data sets.

 


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