Optimal use of ionospheric corrections for wide area augmentation system (WAAS) users [GPS]

With the continuous development of the wide area augmentation system (WAAS), integrity and availability become the paramount challenges for an operational WAAS and its applications. Although recent research has demonstrated the superior performance of the WAAS system under normal conditions, unknown ionospheric irregularities and fast spatial decorrelation might cause the greatest uncertainty and impacts on the availability and continuity of the WAAS system. In this paper, current WAAS ionospheric availability threats and user algorithm limitations are investigated in detail. An optimal ionospheric correction (OPIC) generation algorithm, which combines user local observables and WABS ionospheric corrections in an optimal way, could effectively improve user positioning availability and continuity without sacrificing integrity. Furthermore, independent integrity monitoring for WAAS corrections could become practical using single-frequency receivers when augmented with this scheme, The significance of the OPIC framework are verified by live data from the National Satellite Test Bed (NSTB) network.