Performance Evaluation Method for Ionospheric Grid Information of BDS via Dual-frequency Observations

As one of the principal error sources in satellite navigation system, it is ionospheric delay whose correction accuracy directly affects single-frequency positioning accuracy. There are Klobuchar ionospheric model and ionospheric grid information for single-frequency users, provided by basic navigation service and enhancement service respectively in BeiDou Navigation Satellite System. Ionospheric grid information is broadcast as vertical delay estimates at specified ionospheric grid points (IGPs) with a resolution of 5 degrees and 2.5 degrees in longitude and latitude. To evaluate its performance, it proposed a performance evaluation method via dual-frequency observations. And the feasibility of this method was verified by the ionospheric grid information data from November 2017 to October 2018. Performance evaluation results showed that the effective coverage area of ionospheric grid information basically covers China, with a correction deviation of 1.55 TECU and a correction rate of 86.1%.And it is in winter that the correction accuracy of ionospheric grid information is lower and more fluctuating with a correction bias of 1.95 TECU and a correction rate of 81.5% and, but less than 1.47 TECU of bias and more than 86.5% of rate in other seasons. It is higher in both correction bias and correction percentage during the day than at night.