Low-Cost Precise Positioning Using a National GNSS Network

This article presents an implementation of Real-Time Kinematics (RTK) using a low-cost GNSS receiver and a sparse countrywide reference station network. Furthermore, we assess the feasibility of implementing RTK on a smartphone by comparing the raw GNSS measurements of a commercial smartphone's internal GNSS receiver with a commercial off-the-shelf (COTS) low-cost GNSS receiver. The RTK implementation presented in this paper utilizes the Finnish national GNSS network FinnRef as the RTK base station, either in single-base or network RTK mode; although the main purpose of FinnRef is to maintain the national coordinate system, it is also capable of delivering DGNSS and network RTK data over the NTRIP protocol. The test results show that despite the sparseness of FinnRef, a horizontal position accuracy of 0 : 5 meters or better was achieved for more than 90 % of the time with the COTS receiver both in a dynamic single-base test and in a network RTK experiment using GPS signals only. Obtaining such a positoning performance with low-cost and small-size devices is expected to be useful in various applications, particularly in the field of intelligent transportation systems. Furthermore, the results indicate that the smartphone's GNSS measurements are less precise than those of the COTS receiver and suffer from frequent outliers, making them less favorable for use in precise positioning applications as such.