A Comparison between the TEC Computed using GPS and Ionosonde Measurements

At Dourbes (in Belgium), an ionosonde operated by the Royal Meteorological Institute of Belgium produces an electron concentration profile up to the maximum of the F2 layer. The Royal Observatory of Belgium has installed a Turbo Rogue GPS receiver on the same site. The ionosonde measurements are used to compute the ionospheric electron content (IEC) above Dourbes: in a first step, numerical integration of the measured bottomside electron concentration profile gives the bottomside part and in a second step, analytical integration of a Chapman function modelling the topside electron concentration profile gives the topside part; the parameters of the Chapman function are evaluated using the information contained in the measured bottomside profile. This IEC is compared with the TEC obtained by GPS on a period of 2 years (1995 and 1996). We show that the results of both methods are in very good agreement: the mean and the standard deviation of the differences between the TEC (GPS) and the IEC (ionosonde) computed for this period are respectively 0.46 TECU and 1.72 TECU.