A real-time clock offset estimation method for mitigating orbit prediction errors in multi-GNSS applications

This study proposes a real-time clock offset estimation method that accounts for orbit errors, addressing challenges caused by predicted orbit errors and the slow startup times of simultaneous estimation methods. Utilizing 93 global MGEX tracking stations for real-time clock offset estimation, the accuracy, data processing efficiency, and positioning performance of three estimation schemes were analyzed. The obtained results showed that, compared to the predicted orbit approach, our proposed method significantly improves GNSS satellite orbit accuracy, with BDS satellite accuracy increasing by over 50 %. Regarding clock offset accuracy, the new method, despite imposing strong constraints on radial orbit errors, also enhances GNSS satellite clock offset accuracy, particularly enhancing that of BDS-3 satellites during eclipse periods by approximately 40 %. Compared to the orbit-clock synchronization estimation method, the new method improves computational efficiency. It substantially reduces filtering convergence time, shortening the real-time service initiation time from approximately 125 min to approximately 20 min. Finally, G + C and G + E combination-based kinematic PPP experiments were performed. The positioning outcomes from the three methods achieve centimeter-level accuracy in directions of North, East, and Up, and the new method displays the optimal performance in stability and accuracy. These findings highlight the potential of the new method to enhance GNSS performance in real-time applications.