Evaluation of real-time precise time transfer with Galileo HAS and QZSS MADOCA-PPP service

Abstract The Quasi-Zenith Satellite System Multi-Global Navigation Satellite Systems Advanced Orbit and Clock Augmentation-Precise Point Positioning (MADOCA-PPP) service and Europe’s Galileo High Accuracy Service (HAS) are two freely accessible real-time augmentation services that provide orbit and clock corrections for PPP. This paper presents an evaluation of these two services for precise time transfer. Archived corrections and GNSS observations collected from May 10 to 20, 2024, were processed to assess (i) orbit and clock correction quality and (ii) PPP timing performance under static and kinematic conditions. For MADOCA-PPP, the mean orbit differences in the radial ( R ), along-track ( A ), and cross-track ( C ) directions were 0.033/0.041/0.025 m for GPS, 0.030/0.072/0.047 m for GLONASS, and 0.042/0.056/0.031 m for Galileo. In terms of the standard deviation of the clock deviation, the values of GPS and Galileo systems are smaller than that of the GLONASS system. For the HAS system, the orbital deviation and clock deviation sequences show higher noise levels, and the Galileo orbital deviation shows significant systemic fluctuations during the evaluation period. In the PPP time transmission experiment, the timing statistics obtained by the solution scheme based on MADOCA-PPP correction are close to the final product of Center for Orbit Determination in Europe, while the solution scheme based on HAS shows greater dispersion and decreased frequency stability over the medium-long averaging period, and the sensitivity increases in dynamic tests. Overall, this study analyzes the correction behavior and terminal PPP timing performance of MADOCA-PPP and HAS, which provides a practical reference for real-time precision positioning, navigation and timing applications.