Static PPP over observation time using magic-GNSS: GPS Vs. GLONASS Vs. GPS+GLONASS

This study investigates the performance of static Precise Point Positioning (PPP) as a function of fixing duration using the magic-GNSS free online service. The platform supports processing of GPS-only, GLONASS-only, and combined GPS+GLONASS observations, enabling a direct comparison between individual and integrated satellite systems. The evaluation was conducted under open-sky conditions to minimize multipath effects. Dual-frequency GNSS observations were collected from ten well-distributed stations, each with a continuous 24-hour observation session. Static PPP solutions were generated for fixing intervals starting from 1 hour and progressively increasing up to 24 hours. The 24-hour solution was adopted as the reference to assess the accuracy of shorter observation durations. The results reveal that the GPS-only and GPS+GLONASS solutions are identical, indicating that the magic-GNSS processing strategy relies primarily on GPS observations when they are available. In contrast, GLONASS-only results demonstrate superior performance during short observation periods. Within the first hour, GLONASS achieves lower average absolute errors than GPS by approximately 1.5 cm, 2 cm, 2 cm, 2 cm, and 3 cm in the Easting, Northing, Height, 2D, and 3D components, respectively. The 1 cm accuracy level in the horizontal plane is reached after approximately 7.5 hours using GPS-only observations, compared to only 3 hours using GLONASS-only. For the height component, the same accuracy level is achieved after 7.5 hours and 4 hours, respectively. Furthermore, both systems converge to millimeter-level accuracy with longer observation durations. In the horizontal components, GPS and GLONASS reach approximately 1 mm accuracy after 15 hours and 6 hours, respectively, while in the vertical component, this level is achieved after approximately 14 hours for GPS and 15 hours for GLONASS. These findings confirm that both GPS-only and GLONASS-only PPP can deliver accurate and reliable positioning under open-sky conditions when sufficient observation time and precise ephemerides are used. However, GLONASS-only observations exhibit significantly faster convergence, reaching centimeter-level accuracy in both horizontal and vertical components in a shorter time compared to GPS-only.