Application of ionosphere correction for enhanced multi-GNSS positioning

Currently, the GNSS (Global Satellite Navigation System) and the RNSS (Regional Satellite Navigation System) consist of GPS, GLONASS, BeiDou, Galileo, IRNSS, SBASs, and QZSS. Collectively, the components of GNSS and RNSS are referred to Multi-GNSS. One of the advantages of using Multi-GNSS signals is improvement of poor satellite geometry in severe conditions, such as in urban canyons. However, multipath is a major source of error in GNSS range measurements, and position accuracy is extremely degraded by multipath as well as poor satellite geometry in urban canyons. Therefore, multipath detection algorithm is necessary for precise positioning with multiple GNSS signals. There has been discussion about detection of the multipath effect by using signal strength and residuals. However, these conventional methods are indirect measures of signal quality, not visual monitors. To overcome these problems, a more direct way of detecting the multipath effect is needed. This paper proposes an enhanced method of detecting multipath effect by using a geometry-free combination applied with high-accuracy ionosphere correction. We found that the proposed method is more effective for code relative positioning, however QZS Klobuchar parameters are necessary.