GALILEO HAS overview, comparison with analogues, and assessment of perspective

In 2022, Galileo, the European GNSS, launched the first phase of its HAS (High Accuracy Service) initiative. With free and global corrections for clock delays and satellite orbits, Galileo HAS provides decimeter positioning accuracy without additional ground networks. This research aims to evaluate the advancements in precise positioning technologies, focusing on the Galileo High Accuracy Service (HAS). The study highlights the importance of precision positioning methods, including Standard Point Positioning (SPP), Real-Time Kinematic (RTK), and Precise Point Positioning (PPP). It assesses the performance of Galileo HAS in comparison with other global augmentation services like QZSS CLAS and BeiDou PPP-B2b. The methodology involves a comprehensive analysis of the technical capabilities, accuracy, and operational limitations of HAS through a literature review and comparative analysis of positioning performance data. The results confirm that Galileo HAS achieves decimeter-level accuracy globally, with horizontal accuracy below 20 cm and vertical accuracy below 40 cm. However, it suffers from prolonged convergence times due to the absence of atmospheric and phase bias corrections in its initial phase. The scientific novelty lies in identifying HAS's potential as the first global free PPP correction service via Signal-in-Space (SIS), distinguishing its practical advantages in semi-enclosed environments compared to traditional PPP augmentation systems. The study also emphasizes the unique integration challenges posed by HAS corrections due to proprietary encoding formats. Thee findings underscore HAS's utility in geodesy, mapping, and real-time applications, particularly in resource-constrained settings. However, the research highlights critical areas for improvement, such as implementing atmospheric corrections and phase bias adjustments, to meet real-time precise positioning demands. The conclusions note the undoubted usefulness of such a service as Galileo HAS and review its shortcomings and methods of solving them.