Real-time high-precision positioning for ships in the surrounding waters of China based on BDS-3 PPP-B2b

In maritime environments, the lack of ground-based Internet limits the application of real-time Precise Point Positioning (PPP), making high-precision ship positioning challenging. Through the PPP-B2b service, BDS-3 can provide real-time precise positioning for users in China and its surrounding areas without relying on Internet. Based on orbit, clock, and differential code bias (DCB) corrections from PPP-B2b, this study extends the BDS-3 undifferenced and uncombined dual-frequency PPP model to the multi-frequency model and applies predicted DCB to correct intra-frequency DCB. A BDS-3/GPS dual-system multi-frequency real-time PPP model is then developed. To support receivers with different signal capabilities, eight positioning strategies are designed, including dual-, triple-, four-, and five-frequency combinations for both BDS-3 single-system and BDS-3/GPS integration. Experiments using 23 days of real maritime data show that the dual-system five-frequency strategy achieves the best performance, with convergence time of 7.5 min and horizontal accuracy of 61.7 mm. Furthermore, simulated kinematic experiments are conducted on 10 static stations using PPP-B2b and post-processed precise products, respectively. The results show that positioning performance using PPP-B2b products still shows a certain gap compared to that of post-processed products. Overall, PPP-B2b service provides fast convergence, high accuracy, and real-time positioning for maritime applications in waters surrounding China.