Abstract
Recently, long tunnels are becoming more prevalent in Korea, and exits are added at certain sections of the tunnels. Thus, a navigation system should correctly guide the user toward the exit; however, adequate guidance is not delivered because the global navigation satellite system (GNSS) signal is not received inside a tunnel. Therefore, we present an accurate position estimation system using a magnetic field for vehicles passing through a tunnel. The position can be accurately estimated using the magnetic sensor of a smartphone with an appropriate attitude estimation and magnetic sensor calibration. Position estimation was realized by attaching the smartphone on the dashboard during navigation and calibrating the sensors using position information from the GNSS and magnetic field database before entering the tunnel. This study used magnetic field sequence data to estimate vehicle positions inside a tunnel. Furthermore, subsequence dynamic time warping was applied to compare the magnetic field data stored in the buffer with the magnetic field database, and the feasibility and performance of the proposed system was reviewed through an experiment in an actual tunnel. The analysis of the position estimation results confirmed that the proposed system could appropriately deliver tunnel navigation.
Highlights
Vehicle navigation services are essential for drivers and can be used with smartphones, regardless of time, weather, or location
Since the attitude of the smartphone is different from the DB frame, it can be seen that the magnetic field pattern of user data is quite different with that of DB data like Figure 14a,c,e
Existing navigation systems based on global navigation satellite system (GNSS) cannot provide accurate positions in tunnel environments
Summary
Vehicle navigation services are essential for drivers and can be used with smartphones, regardless of time, weather, or location (under coverage). Most of these services are available for free and operate based on a global navigation satellite system (GNSS) [1], through which users can accurately determine their current location in real time. GNSS can accurately estimate the user position for a clear line of sight between the user and satellite. Numerous multipaths occur in an urban area with several tall buildings, and the GNSS performance is degraded. Accurate positioning cannot be determined in places where GNSS signals are not received such as indoors or tunnels [2]. As the current navigation system relies on only the GNSS, the navigation service is restricted in places with inferior GNSS signal quality
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