Network Modelling Considerations for Wide-area Ionospheric Corrections

Augmentation plays a critical role in the integrity and accuracy of global navigation satellite system (GNSS) positioning. The user range error can be significantly improved using precise satellite orbit and clock corrections, as well as atmospheric delay predictions. This paper focuses on the process of generating corrections for the signal delay/advance caused by the ionosphere. We analyze the impact of three variables on the accuracy of these corrections: the input slant ionospheric delays, the mathematical model, and the network configuration. When the input delays are derived from the precise point positioning (PPP) methodology, we show that ambiguity resolution (PPP-AR) offers a 20-50% reduction in the RMS error of predicted delays over float ambiguity estimates. Among the models evaluated, the dual-layer and conical models can reduce RMS errors by more than 50% over the single-layer model during moderate ionospheric activity. Finally, for the days analyzed, increasing inter-station distances from 75 km to 150 km only deteriorates RMS errors by 10%.