Analysis of marine real-time PPP accuracy with the BDS-3 PPP-B2b service

For high-precision maritime positioning, traditional technologies, e.g., Network Real-Time Kinematic (NRTK) technology and the Real-time Service (RTS) provided by the International GNSS Service (IGS), suffer limitations owing to Internet communication quality. In addition, commercial Precise Point Positioning (PPP) services remain unaffordable for widespread adoption. BeiDou Navigation Satellite System (BDS-3) represents a better solution, as it offers a viable alternative by broadcasting the PPP-B2b signal, thereby providing a cost-free, real-time PPP service to maritime users near the Chinese coastline. Consequently, this service is instrumental in various maritime applications, including environmental surveying, fleet navigation, and sea-to- air relative positioning. This paper first delineates the PPP-B2b signal's content and correction algorithms, then constructs a real-time PPP scheme after orbit and clock correction, subsequently performs accuracy evaluation on these corrections, and finally analyzes the marine positioning performance of PPP-B2b. It is revealed that the accuracies of the PPP-B2b orbit are superior to 0.028, 0.039, and 0.077 m for the BDS-3 MEO, BDS-3 IGSO, and GPS satellites, while those of clock offset are superior to 0.12, 0.36, and 1.14 ns, respectively. Compared to traditional broadcast ephemerides, the PPP-B2b signal offers an improvement of 6.5% and 21.1% for BDS-3 orbit and clock offsets and 26.7% and 15.6% for GPS orbit and clock offsets. Using PPP-B2b in marine contexts, the BDS-3, GPS, and combined configurations yield positioning accuracies of 8.9, 11.8, and 6.0 cm, with convergence of approximately 114, 69.5, and 19 min, respectively. The dual-system PPP distinctly provides superior accuracy and quicker convergence. Upon convergence, the dynamic PPP accuracy achieves a range from centimeters to decimeters, meeting the performance standard of BDS open services. These analyses demonstrate that PPPB2b holds significant potential for marine location-based applications.