Dual-frequency static positioning under open-sky conditions: AUSPOS Vs. Trimble RTX-PP

This study presents a comprehensive evaluation of two widely used online GNSS processing services, namely the Australian Positioning Open Service (AUSPOS) and Trimble RTX-PP, for dual-frequency static positioning under open-sky desert conditions. The analysis is based on ten 24-hour GNSS datasets collected from geographically distributed locations across Libya using dual-frequency receivers operating in static mode. Three processing configurations were investigated: AUSPOS (GPS-only), Trimble RTX-PP GPS-only, and Trimble RTX-PP GPS+GLONASS. Positioning performance was evaluated as a function of observation duration, with processing intervals ranging from 1 to 24 hours. The fully converged 24-hour solution generated by each service was adopted as the reference benchmark.
The results reveal substantial differences in convergence behavior and positioning performance, particularly during short observation sessions. Trimble RTX-PP demonstrated significantly faster convergence and higher accuracy than AUSPOS throughout the observation period. After one hour of observations, RTX-PP achieved approximately 2.0 cm and 1.4 cm three-dimensional (3D) accuracy for the GPS-only and GPS+GLONASS configurations, respectively, whereas AUSPOS achieved approximately 83 cm 3D accuracy. The inclusion of GLONASS observations further enhanced RTX-PP performance by improving satellite geometry and accelerating solution convergence. As observation duration increased, the accuracy of all solutions improved, and millimeter-level precision was eventually achieved. However, RTX-PP consistently maintained superior accuracy and stability, reaching high-precision positioning substantially faster than AUSPOS. The results demonstrate the advantages of advanced processing strategies and multi-constellation observations in reducing convergence time and improving positioning performance. The findings highlight the significant influence of processing methodology, observation duration, and satellite constellation availability on static GNSS positioning accuracy and provide practical guidance for selecting appropriate online processing services for high-precision surveying and geodetic applications.