Electron density profiles determined from tomographic reconstruction of total electron content obtained from GPS dual frequency data: first results from the South African network of dual frequency GPS receiver stations

Dual frequency receivers of the global navigation satellite system (GNSS) of the recently established South African Network of more than 40 geodetic grade GPS base station receivers provide a valuable tool by means of which the ionospheric conditions over Southern Africa can be determined with a better time and spatial resolution than is currently possible using only the available three ionosonde sites. Electron density profiles obtained by tomographic reconstruction of GPS derived total electron content measurements, as augmented with ionosonde measurements has the potential to become a tool to quantify ionospheric variability and investigate ionospheric dynamics and medium- and smaller-scale ionospheric structures such as travelling ionospheric disturbances. The local network of dual frequency GPS reference stations have been deployed by various agencies in South Africa to provide correction data for geodetic and surveying applications. This paper presents the first results of ionospheric tomography using data from the Trignet network of GPS stations in South Africa. The tomographic imaging is done by means of the MIDAS program. Verification is provided through comparison with electron density profiles derived from the three South African ionosonde sites.