High-precision ionospheric modeling and its application in positioning under geomagnetic storm conditions

Ionospheric delay, a crucial error source in precise point positioning (PPP) technology, can significantly hamper positioning accuracy and dependability, particularly during geomagnetic storm conditions. This study presents a high-precision ionospheric model to address this challenge. Initially, total electron content (TEC) is retrieved from the global ionosphere map (GIM) and subtracted from the TEC derived from undifferenced and uncombined PPP data to derive differential TEC (dTEC). Subsequently, a polynomial model of dTEC is established, correlating it with the disturbance storm time (Dst) index. This model is then utilized to compute dTEC and correct the TEC estimate, resulting in an accurate and reliable TEC value. Ultimately, this refined TEC serves as prior ionospheric information for PPP positioning. To validate the positioning performance of our proposed method, positioning experiments proceeded with observational data from six stations at various latitudes from September 6 to 9, 2017. The findings indicate that with the imposition of the high-precision ionospheric model, convergence times to achieve a 10cm accuracy in the East-North-Up (ENU) coordinates are approximately 18 min, 18 min, and 15 min, respectively. In contrast, devoid of the ionospheric model, achieving the same level of convergence takes approximately 35 min, 38 min, and 40 min. Furthermore, in the event of geomagnetic storms, the application of the high-precision ionospheric model substantially reduces positioning errors, with maximum errors in the ENU coordinates decreasing from 0.8m, 0.7m, and 1.2m to 0.4m, 0.35m, and 0.6m, respectively.