Yafeng Wang

Aiming to overcome the dual limitations of UPD quality and terminal algorithms on PPP-AR performance, we propose a real-time multi-GNSS strategy combining improved UPD estimation and optimized BIE. Within this framework, the UPD enhancement ensures high-quality correction products, while the optimized BIE method improves the robustness of ambiguity resolution for users. The enhanced UPD estimation process significantly reduces the root mean square (RMS) errors of narrow-lane (NL) UPD residuals to 0.041 cycles, 0.043 cycles, and 0.094 cycles for GPS, Galileo, and BDS systems, respectively, thereby improving the precision and stability of the UPD products. For ambiguity resolution, the improved BIE method is applied with an anomaly satellite exclusion strategy and is systematically compared with the traditional BIE method and the partial least-squares ambiguity decorrelation adjustment (Par-LAMBDA) method. Compared to the original BIE method, the improved BIE approach demonstrates a significant enhancement in performance, increasing the ambiguity fixing rate from 77.8% to 96.9%, reducing the convergence time from 5.12 minutes to 2.07 minutes, and decreasing the RMS of positioning errors in the east, north, and up directions by 44.4%, 25.0%, and 14.7%, respectively. Compared to the Par-LAMBDA method, the improved BIE method further increases the ambiguity fixing rate from 94.4% to 96.9%, and reduces the average convergence time from 3.31 minutes to 2.07 minutes. These results indicate that the proposed strategy significantly enhances the performance of real-time PPP, providing critical support for high-precision real-time navigation applications.

High-precision DCBs are essential for effective multi-frequency and multi-constellation GNSS integration, especially in processing compatible signal observations. This study utilizes data from MGEX, iGMAS, and CORS stations to estimate and analyze long time series of BDS/GNSS DCBs, focusing on stability and influencing factors. Results indicate that DCBs for the same signal, but different channels exhibit similar ranges and trends. Among BDS DCBs, those from satellites with rubidium atomic clocks are more stable than those with hydrogen atomic clocks. An upgrade and maintenance of BDS in late 2022, reported by NABU, likely contributed to DCB jumps. BDS-compatible signal DCBs show weaker stability compared to GPS and Galileo. Variations in GNSS signal processing and receiver algorithms also impact DCB stability. Converting DCBs to OSBs and performing RMS statistics revealed that smaller differences between signals increase the susceptibility of observation equations to observation quality.