In the RTK(Real-Time Kinematic) applications of GNSS(Global Navigation Satellite Systems), CSC(Carrier-Smoothed-Code) filtering method is widely utilized for centimeter-level accuracy. In CSC filtering, carrierphase observables play a crucial role. However, carrier-phase observables are vulnerable to cycle slips especially in urban area. To mitigate the effects of cycle slips, Doppler observables can be considered as the good substitute for carrier phase observables. For efficient utilization of Doppler observables, accuracy deterioration due to increased noise magnitude needs to be overcome. The Doppler errors are not uniform but time-varying due to the dependence on complex signal environments. To consider the variability of Doppler errors, adaptive filtering technique would be a good candidate to improve the positioning accuracy. In this paper, an SNR(Signal-to-Noise Ratio)-based adaptive filter is proposed for robust positioning under dynamic signal environments. In the proposed method, SNR observables are utilized to estimate variance of Doppler observables. To assess the feasibility of the proposed method, two experiments were performed with real measurements.

Keywords: CSC(Carrier-Smoothed-Code), Adaptive, RTK(Real-Time Kinematic), SNR(Signal-to-Noise Ratio)