A Doppler Smoothing Filter using Carrier Phase and Application to RTK

Recently, in the field of ITS (Intelligent Transportation System), accurate and precise position of a vehicle in the street is more demanding. They want to know which lane a car is driving in. The GNSS RTK could provide this accuracy. But, in urban street, due to its environment, the conventional code and carrier based RTK can’t be a practical solution. The Doppler measurement from GNSS receiver could be considered as one more measurement to solve this problem. A carrier smoothing of Doppler measurement using Kalman Filter is proposed in this paper. This carrier smoothing technique for Doppler measurement can improve Doppler measurement noise level, especially for low cost GNSS receiver. For more robust RTK float solution, this carrier smoothed Doppler measurement is included in double differenced RTK measurement and the velocity estimation performance is much improved. And the innovation and covariance of the smoothing filter is found to be efficient in detecting carrier cycle slip. Field test in urban area shows effectiveness of using carrier smoothed Doppler measurement in RTK for precise positioning of vehicle in the street.