A new approach to map matching for in-vehicle navigation systems: The rotational variation metric

The purpose of the map-matching module of an in-vehicle navigation system is to locate the position of the vehicle relative to the map data that is referenced by the system. Map-matching allows the display module to accurately depict to the driver the position of the vehicle on the map and facilitates operations such as route calculation, rerouting, etc... The basic approach is to compare the historical vehicular path to possible candidate paths on the map, where candidate paths are the paths on the map which lie within the general vicinity of the vehicle at any instant in time. The candidate map path which best matches the vehicle path is the most likely path on which the vehicle is located. The map display module and other modules of the navigation system use this new position for further processing. Such a map-matching module is also used in vehicle safety applications such as Adaptive Cruise Control (ACC) where the velocity of the vehicle is adjusted based on point curvature of the road network. This paper presents a new metric, the Rotational Variation Metric, which provides a new method for comparing vehicular and map paths for the purpose of map-matching. The method described here is effective while being both intuitive and computationally non-intensive.