System Description: Map-Matching

Map-matching compares a current location detected by the method in the "Location Detection Principle" with the road map data from map SD card.

Fig 1: Identifying Map-Matching

Courtesy of NISSAN NORTH AMERICA, INC.

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 map-matching, alternative routes to reach the destination will be shown and prioritized after the road on which the vehicle is currently driven has been judged and the vehicle mark has been repositioned.
  Fig 2: Identifying Actual Vehicle Traced Route

  Courtesy of NISSAN NORTH AMERICA, INC.

  Alternative routes will be shown in different order of priority, and the incorrect road can be avoided if there is an error in distance and/or direction.

  They are of the same priority if two roads are running in parallel. Therefore, the vehicle mark may appear on either of them alternately, depending on maneuvering of the steering wheel and configuration of the road.

• Map-matching does not function correctly when a road on which the vehicle is driving is new and not recorded in the map SD card or when road pattern stored in the map data and the actual road pattern are different due to repair.
  Fig 3: Identifying Actual Vehicle Traced Route

  Courtesy of NISSAN NORTH AMERICA, INC.

  The map-matching function may find another road and position the vehicle mark on it when driving on a road not present in the map. Then, the vehicle mark may change to it when the correct road is detected.

• Effective range for comparing the vehicle position and travel direction calculated by the distance and direction with the road data read from the map SD card is limited. Therefore, correction by map-matching is not possible when there is an excessive gap between current vehicle position and the position on the map.