Navigation System: Map-Matching

WARNING: This page is about a different car, the 2008 Infiniti FX45 and 2008 Infiniti FX35. However, it is still accessible from the selected car via links, so may be relevant.

Map-matching compares a current location detected by the method in the "Location Detection Principle" with a road map data from DVD-ROM stored in DVD-ROM drive.

NOTE: The road map data is based on data stored in the DVD-ROM.

Fig 1: Identifying Map-Matching

Courtesy of NISSAN MOTOR CO., U.S.A.

The vehicle position may not be corrected under the following circumstances and after driving for a certain time when GPS information is difficult to receive. In this case, the current-location mark on the display must be corrected manually.

In map-matching, alternative routes are prepared and prioritized in addition to the road judged currently driven. Due to the distance and/or direction error, the incorrect road may be prioritized and current-location mark may be repositioned to the wrong road.
When two roads are running in parallel, they are judged to the same priority. Therefore, the current-location mark may appear on either of them alternately, depending on maneuvering of the steering wheel and configuration of the road.

Fig 2: Identifying Actual Vehicle Traced Route
Courtesy of NISSAN MOTOR CO., U.S.A.
Map-matching does not function correctly when a road on which the vehicle is driving is new and not recorded in the DVD-ROM, or when road pattern stored in the map data and the actual road pattern are different due to repair.
When driving on a road not present in the map, the map-matching function may find another road and position the current-location mark on it. Then, when the correct road is detected, the current-location mark may change to it.

Fig 3: Identifying Vehicle Route Indicated On Map Display
Courtesy of NISSAN MOTOR CO., U.S.A.
Effective range for comparing the vehicle position and travel direction calculated by the distance and direction with the road data read from the DVD-ROM is limited. Therefore, when there is an excessive gap between current vehicle position and the position on the map, correction by map-matching is not possible.