A spatial analysis of global navigation satellite system stationswithin the context of the African geodetic reference frame

Abstract

Permanent Global Navigation Satellite Systems (GNSS) stations that are operating within the African Geodetic Reference Frame (AFREF) are contributing data to the datum realizations at global, regional and local levels. The infrastructure supports development and administrative functions of African governments, the public and investors throughout the African continent. However, African stations with high quality and continuous data that have been acquired over several decades are limited, which result in a non-uniform network. This means that additional station investment are required in Africa for new stations to contribute to the AFREF project. An assessment of the spatial distribution and densification of GNSS stations that contribute to AFREF ensure future geometrical improvements in the network have the most impact. Established GNSS stations within AFREF network contribute data for the realization of the International Terrestrial Reference Frame (ITRF), International GNSS Service (IGS) products and local AFREF solutions. This study contributes to AFREF through an improved understanding of the progress, identifies countries that have either adequate or inadequate permanent GNSS stations and informs planning and decisions on sites for new GNSS station installations. In turn, the result forms the basis for evaluating the impact of locations, proximity, neighbourhood and distribution of GNSS stations in AFREF static coordinates and station velocities computations. The study concludes that due to current sparse and uneven geometric distribution of GNSS stations, a strategic and planned densification of AFREF stations is essential.