The Use of Multiple GNSS Constellations with Strict Quality Constraints for Achieving High Accuracy in Urban Environments

H. Tokura, H. Yamada, N. Kubo, S. Pullen

Abstract:	The availability of Global Navigation Satellite System (GNSS) applications is anticipated to improve over the next few years because of the introduction of new positioning satellites, forming what is called “multi-GNSS”. Asia in particular will be able to benefit from multi-GNSS using the U.S. Global Positioning System (GPS), the Russian GLONASS, the European Galileo, the Chinese Navigation Satellite System (BeiDou), and the Japanese Quasi-Zenith Satellite System (QZSS). The combined multi-GNSS signals are capable of improving satellite availability for both standalone and differential positioning. At present, the potential for high-accuracy automobile navigation using GNSS is constrained by severe multipath and poor satellite geometry, especially in "urban canyons" in large cities. With differential GNSS positioning, inconvenient system time differences can be removed by reference-station processing, allowing user receiver position to be calculated with integrity from four or more visible satellite signals. Therefore, in the future, we can tightly screen the quality of the numerous multi-GNSS measurements to enhance positioning performance in urban environments. In this paper, we use two measured quantities to detect satellite signals containing multipath error and a pressure sensor to detect large altitude positioning errors. The first of these metrics is received signal strength as measured by the estimated carrier-to-noise ratio (C/N0). The second metric is the pseudo-range error residual from Receiver Autonomous Integrity Monitoring, or RAIM, which is a well-known technique for checking the quality of ranging measurements. To examine the effectiveness of the proposed techniques, positioning tests were performed in a dense urban environment in Nagoya, Japan. We set up a GNSS receiver antenna on the roof of a car and moved around in this urban-canyon environment. The results to date suggest that the techniques discussed above are effective for detecting measurements containing severe multipath errors. Comparing positioning accuracy with the detected measurements included vs. removed demonstrates that excessive positioning errors can be reduced using these techniques. In conclusion, it has been shown that using satellites from multiple GNSS satellite constellations makes it possible to detect and eliminate measurements with large multipath errors, making it of great value in the urban environment.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	488 - 498
Cite this article:	Tokura, H., Yamada, H., Kubo, N., Pullen, S., "The Use of Multiple GNSS Constellations with Strict Quality Constraints for Achieving High Accuracy in Urban Environments," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 488-498.
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