Static GPS-alone solution over fixing time using AUSPOS free online service

This study evaluates the performance of dual-frequency static solution as a function of observation duration using the AUSPOS free online service under a GPS-only processing strategy. AUSPOS is an openly available online GPS data processing service provided by Geoscience Australia and relies on a network-based, double-difference relative positioning strategy. It takes advantage of both the International GNSS Service (IGS) Stations Network and the IGS product range, as well as the Asia-Pacific Reference Frame Network (APREF) station data and coordinate solutions. AUSPOS works with data collected anywhere on Earth. The analysis is based on ten GNSS datasets collected from different locations across Libya using dual-frequency receivers operating in static mode under open-sky desert conditions. Each dataset consists of continuous 24-hour observations, with processing performed at fixing intervals ranging from 1 to 24 hours. The fully converged 24-hour solution was adopted as the reference benchmark for accuracy assessment in Easting, Northing, Height, 2D, and 3D components. The results show that static double-difference relative positioning performance is strongly dependent on observation time. After one hour, relatively large positioning errors are observed, reaching approximately 32 cm, 19 cm, and 75 cm in the East, North, and Height components, respectively, corresponding to 38 cm and 83 cm in 2D and 3D accuracy. However, a significant improvement is observed with increasing observation duration, where centimeter-level accuracy (~2 cm) is achieved across all components after two hours of data processing. Further extension of the observation time leads to gradual refinement of the solution, reaching millimeter-level accuracy after approximately 11 hours in Easting, 15 hours in Northing, and 16 hours in Height, after which the solution stabilizes. These results confirm that GPS-only static solution using AUSPOS is capable of delivering high-precision positioning under open-sky conditions, but its convergence is relatively slow and highly dependent on observation duration. The use of geographically distributed datasets further highlights the influence of satellite visibility and geometry on positioning stability and accuracy. Overall, the findings emphasize that sufficient observation time is essential to achieve reliable centimeter to millimeter level accuracy in GPS-only static double-differencing relative processing.