Development and accuracy analysis of a regional ionospheric model for the middle reaches of the Yangtze River using multi-source data

The sparse distribution of international GNSS service (IGS) reference stations in China has led to the reduced accuracy of the global ionosphere map (GIM) data within the region, limiting the precise measurement of fine-scale ionospheric variations. In the present work, a regional ionospheric model for the middle reaches of the Yangtze River was constructed utilizing data from the Hubei Continuous Operational Reference System (HBCORS), the crustal movement observation network of China (CMONOC), and IGS. Additionally, we assessed the accuracy of the proposed ionospheric model. The results show that both the estimated differential code bias (DCB) values for 32 satellites and those published by the Center for Orbit Determination in Europe (CODE) are under 0.3ns. Furthermore, the DCB values of the 45 observation stations contributing to the proposed model demonstrate stable measurements, all below 0.3ns. The difference between the ionospheric vertical total electron content (VTEC) values in the middle reaches of the Yangtze River and those obtained through linear interpolation from IGS exhibits a maximum root mean square (RMS) value of 1.72TECu and a maximum standard deviation (STD) value of 1.46TECu. For stations in HBCORS that were not included in the modeling process, leveraging the CODE global ionospheric model precise point positioning (PPP) resulted in maximum errors of 0.25m, 0.24m, and 0.48m in the N, E, and U directions, respectively. However, using the regional ionospheric model PPP in the middle reaches of the Yangtze River yielded maximum errors of 0.14m, 0.18m, and 0.21m in the N, E, and U directions, respectively. Compared to the CODE global ionospheric model, the regional ionospheric model PPP in the middle reaches of the Yangtze River enhanced positioning accuracy by 49.91%, 35.15%, and 53.53% in the N, E, and U directions, respectively.