A global ionospheric range error correction model for single frequency GNSS users

The basic approach of a model of the Total Electron Content (TEC) that has recently been developed at DLR is presented and the performance is discussed in comparison with GNSS single frequency correction models such as the Klobuchar and the NeQuick model in particular for low latitude conditions. The empirical approach describes functions on season, local time, geographic/geomagnetic location and solar activity conditions approximated by the solar radio flux index F10.7. The 12 coefficients are derived from global TEC data provided by the University of Berne over more than half a solar cycle (1998-2007). It has been found that both the global Neustrelitz TEC Model (NTCM-GL) and the NeQuick model show a better performance than the Klobuchar model by a factor of about two. Nevertheless, NTCM and NeQuick models deviate considerably at low latitudes indicating that modelling of the low latitude ionosphere is a challenging task that needs further research. Since NTCM requires only 12 coefficients it is much easier to handle than NeQuick and might also be used as a single frequency correction model for single frequency GNSS applications like the Klobuchar model currently used in GPS