Modeling regional ionospheric delay with ground-based BeiDou and GPS observations in China

The Compass/BeiDou system is currently being built as a navigation constellation consisting of 16 navigation satellites. Construction of these satellites will significantly increase the number of visible satellites over the Chinese mainland and improve the geometry of satellite positioning. We obtained data by simulation and measurements to analyze the influence of BeiDou regarding the longest observation arc and the ionosphere piercing point distribution. A regional ionosphere delay model is built using data measured by BeiDou only, global positioning system (GPS) only, and the dual-satellite system. The results show that the model accuracy for BeiDou only is as accurate as the single GPS system in the middle and lower latitudes, while a deviation becomes noticeable at high latitudes and over marginal areas where observations are fewer due to lack of BeiDou satellites. With the current distribution of the satellites and tracking stations, it appears that the dual-satellite system could significantly improve the ionospheric model in China and the accuracy of differential code bias (DCB) determination. The experimental results also show that the BeiDou satellite DCB is quite stable, with a monthly maximum change of 1.8 ns.