QZSS Contribution to Multi-GNSS Static Positioning Accuracy and Performance across the Asia-Pacific Region
Abstract
The Quasi-Zenith Satellite System (QZSS) is a Japanese regional constellation designed to augment the Global Positioning System (GPS) and to improve positioning availability and accuracy over the Asia-Pacific region. Although the contribution of QZSS has been examined extensively for single-frequency Precise Point Positioning (PPP) and simulated Real-Time Kinematic (RTK) scenarios, its added value in dual-frequency multi-GNSS static relative positioning across a wide range of baseline lengths has received comparatively little attention. This study evaluates the contribution, accuracy and performance of QZSS within a combined GPS + GLONASS + Galileo + BeiDou + QZSS solution using real observations from twelve International GNSS Service (IGS) stations in Taiwan, the Philippines and Australia. Seven baselines ranging from 11.8 km to 2763.9 km were processed for four independent 24-hour sessions (11 April, 30 May, 19 July and 8 September 2021) with two independent software packages, Topcon MAGNET Tools (multi-GNSS relative processing) and the CSRS-PPP online service (GPS/GLONASS PPP), which were used as mutually independent references. For short and medium baselines (11.8-247.7 km) the coordinate and distance differences between the two solutions remained at the few-millimetre-to-few-centimetre level, whereas BeiDou-only and QZSS-only solutions degraded to a maximum of about 15 m on the longest baselines. Adding QZSS to the multi-GNSS solution improved the horizontal accuracy by approximately 10%, and this improvement increased with increasing Position Dilution of Precision (PDOP). The results confirm that, despite comprising only three to four operational satellites during the observation period, QZSS provides a measurable and geometry-dependent contribution to multi-GNSS static positioning in the Asia-Pacific region, while millimetre-level accuracy cannot be guaranteed for all baselines and all sessions.