Ionospheric Anomaly Detection to Support the BDSBAS

Corrections and integrity bounds of the ionospheric delay generated at the Satellite-Based Augmentation System (SBAS) for aviation users may confront a wide range of ionospheric conditions over its update interval. Ionospheric irregularities affecting Single Frequency (SF) SBAS can cause the risk of service integrity and a loss of service continuity. The aim of the Ionospheric Anomaly Detection (IAD) scheme is to detect the effect of ionospheric irregularities on the SBAS SF service operational capability over China. It will help in establishing statistical anomaly models and then provides a high level of service for aviation users. The IAD scheme uses a fusion protocol to reach consensus among subdetectors, which monitor different ionospheric features. Moreover, the threshold of every sub-detector is derived based on system availability. We analyze the IAD scheme by practical ionosphere observations recorded at the crustal movement observation network of China in 2015. It successfully identifies ionospheric anomalies affecting SF SBAS and conforming with physical characteristics. Furthermore, it provides sufficient detection reliability. The statistical results illustrate that the difference of 95% residual error for post-ionosphere correction between normal and anomalous zones is between 1.4 m and 3.2 m. The average value is 2.1723 m. Additionally, there exist two types of ionospheric anomalies affecting SBAS SF service over China. The range is mainly at latitude 15°-35°N. The occurrence time is mainly at GPS time 4-15 h and 12-19 h, respectively.