Static PPP Over Observation Time: Magic-GNSS Vs. Qinertia Cloud

This study presents a comparative evaluation of static Precise Point Positioning (PPP) performance as a function of fixing duration using two free online processing services, namely magic-GNSS and Qinertia Cloud. The analysis considers different constellation configurations, including GPS-only, GLONASS-only, and combined GPS+GLONASS, under ideal open-sky conditions to eliminate multipath effects and isolate the impact of satellite geometry and processing strategies. Dual-frequency GNSS observations from ten well-distributed stations, each with 24-hour datasets, were processed using fixing intervals ranging from 1 to 24 hours, with the fully converged 24-hour solution adopted as the reference benchmark. The results reveal notable differences between the two platforms in terms of constellation utilization and performance. In the magic-GNSS solution, GPS-only and GPS+GLONASS results are effectively identical, indicating that the processing strategy relies primarily on GPS observations when available. In contrast, GLONASS-only observations exhibit significantly faster convergence, outperforming GPS during short observation periods. Within the first hour, GLONASS achieves lower average absolute errors than GPS by approximately 1.5–3 cm across position components and reaches the 1 cm accuracy level after about 3–4 hours, compared to approximately 7.5 hours for GPS. Millimeter-level accuracy is achieved by both systems with longer observation durations, although GLONASS demonstrates faster horizontal convergence. Conversely, the Qinertia Cloud results confirm the advantage of multi-constellation integration, where the combination of GPS+GLONASS consistently improves solution robustness and stability compared to GPS-only. The enhancement is most pronounced during the early convergence stage, with error reductions of approximately 2–4 cm across all components within the first hour. While the accuracy improvement becomes less significant over longer durations, the inclusion of GLONASS effectively reduces solution dispersion and mitigates outliers, leading to more stable positioning results. Overall, the findings highlight that PPP performance is strongly influenced by both the processing strategy and constellation configuration. While magic-GNSS emphasizes GPS dominance with limited benefit from integration, Qinertia Cloud demonstrates clear advantages of multi-constellation processing. Despite these differences, both studies agree that integrating GLONASS or using it independently significantly enhances convergence speed, particularly during short observation periods, while long-duration observations enable all configurations to achieve centimeter- to millimeter-level accuracy.