As use of satellite navigation system of smartphones and car navigation systems become more usual in populated areas and cities, need for the GNSS position accuracy is consistently increasing. In urban environments, performance of satellite navigation is usually degraded by tall buildings, and it is very difficult to suggest a generalized method because the multipath and NLOS errors are user specific errors that cannot be removed by the DGNSS (Differential GNSS)/RTK (Real Time Kinematic) techniques. Multipath/NLOS error estimation algorithm using CMC (Code Minus Carrier phase) variation has been suggested to reduce this user specific error and a previous work showed that the error can be reduced to 5m in a deep urban area. The algorithm should be applied with a starting position with known coordinate, so this algorithm should be used under very limited conditions. In this paper, we propose a switching technique from a general DGNSS/RTK to the CMC-based multipath/NLOS error mitigation method. After determining the validation of the current positioning mode by residual analysis, it automatically switches to CMCbased positioning if it determined the current position to be unreliable. In order to verify the applicability of algorithm in urban areas, a dynamic test was performed in Teheran-ro, Seoul, which is one of the most challenging area to get good quality GNSS signals.

Keywords: multipath, urban positioning, switching algorithm