Kinematic PPP in Free-Multipath Open-Sky: CSRS-PPP Vs. Qinertia Cloud

This study evaluates and compares the performance of kinematic Precise Point Positioning (PPP) using two freely available online processing services, namely the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) and Qinertia Cloud, under open-sky conditions with negligible multipath effects. Dual-frequency GNSS observations collected continuously for 24 hours from ten well-distributed reference stations across Libya were processed under two configurations: GPS-only and combined GPS+GLONASS. The performance assessment was carried out using several statistical indicators, including the Average Absolute Error (AAE), Maximum Absolute Error (MAE), Root Mean Square Error (RMSE), and the percentage of gross errors exceeding 5 cm in the horizontal components and 10 cm in the height component. The results demonstrate that both services are capable of delivering reliable centimeter-level kinematic PPP solutions, while the integration of GLONASS observations generally improves positioning accuracy and solution reliability. CSRS-PPP exhibits the best overall performance under both processing configurations, achieving RMSE and AAE values below 2 cm in all coordinate components and eliminating gross errors entirely in the combined GPS+GLONASS solution. In addition, the maximum absolute errors obtained from CSRS-PPP remain limited to approximately 10 cm and 7 cm for GPS-only and GPS+GLONASS processing, respectively. Qinertia Cloud also provides high-quality solutions, particularly when multi-constellation processing is employed. The integration of GLONASS reduces the RMSE values in the East, North, and Height components from approximately 2.5 cm, 4 cm, and 6.5 cm to about 2 cm, 1.5 cm, and 2 cm, respectively, while significantly decreasing the percentage of gross errors and reducing the maximum absolute errors in all coordinate components. Overall, the comparative analysis confirms the effectiveness of multi-constellation GNSS processing for improving kinematic PPP performance through enhanced satellite geometry and increased observation redundancy. Although both online services provide accurate and reliable solutions suitable for high-precision kinematic applications, CSRS-PPP demonstrates slightly superior consistency and robustness, whereas Qinertia Cloud offers competitive centimeter-level performance, particularly when GPS and GLONASS observations are combined.