Potential of Locally Enhanced MADOCA PPP as a Positioning Infrastructure for the Asia-Pacific

Ken Harima, Suelynn Choy, and Kazutoshi Sato

Peer Reviewed

Abstract:	The Quasi-Zenith Satellite System (QZSS) is a Regional Navigation Satellite System in development by Japan. The QZSS is expected to reach its first operational stage in 2018, operating as a GNSS augmentation system that covers East-Asia and Oceania. The 4 GPS compatible QZSS satellites will enhance the satellite availability of GPS users in the region, while augmentation messages transmitted by its L1S, L5S and L6 signals will be used to enhance accuracy GNSS positioning. For an area of coverage such as the QZSS visibility range, practical GNSS augmentation systems for high accuracy applications will be based Precise Point Positioning (PPP) technique. Real-time products for PPP based on the Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis (MADOCA) are being considered for transmission by the QZSS. It is highly likely that very similar products will be available from the QZSS accuracy enhancement messages. For areas that enjoy proximity of continuously operating reference station (CORS) differential techniques like RTK will give better performance, particularly in terms of time of convergence. However, these systems have the disadvantage of only working in side or the proximity of CORS networks. A positioning system for the QZSS area of coverage will thus be one that takes advantage of CORS if there are available but preserves the ability to revert to the QZSS based PPP when no nearby stations are available. The present study evaluates the performance of the MADOCA products both in standalone PPP and in locally enhanced PPP. In its current state, MADOCA products contain precise orbit and clock corrections for GPS, GLONASS and QZSS. PPP solutions using GPS and GLONASS constellations were tested in this study. Ionospheric corrections were calculated for GPS only. Standalone PPP is able to have RMS errors of 9 cm in horizontal positioning with a time of convergence of 114 minutes for sub-decimeter accuracy. Locally enhanced PPP was able to achieve an horizontal accuracies of 4.8 to 6.6 cm depending on the network density with 64 to 78% of solutions achieving sub-decimeter accuracy within 2 minutes. These results were obtained without solving integer ambiguities. Results for real-time tests using CLK91 products from the French Space Agency CNES are also presented to hint at the potential performance when the MADOCA system reached maturity, for these tests horizontal accuracy on the 2-3 cm range was achieved with convergence times below 2 minutes for locally enhanced PPP, although up to a few hour were necessary for PPP.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	698 - 712
Cite this article:	Harima, Ken, Choy, Suelynn, Sato, Kazutoshi, "Potential of Locally Enhanced MADOCA PPP as a Positioning Infrastructure for the Asia-Pacific," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 698-712. https://doi.org/10.33012/2017.15102
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