System Description: Map-Matching
Map-matching repositions the vehicle on the road map when a new location is judged to be more accurate. This is done by comparing the current vehicle position (calculated by the normal position detection method) from the map data stored in the HDD (Hard Disk Drive).
There is a possibility that the vehicle position may not be corrected in the following case, or when vehicle is driven over a certain distance or time in which GPS information is hard to receive. Manually correct the current location mark on the screen.
- In map-matching, several alternative routes are prepared and prioritized in addition to the road detected as currently being driven on.
Therefore, due to errors in the distance and/or direction, an incorrect road may be prioritized, and the current location mark may be repositioned to the incorrect road.
If two roads are running parallel, they are of the same priority. Therefore, the current location mark may appear on either of them alternately, depending on steering wheel movement and road configuration, etc.
- Map-matching does not function correctly when road that the vehicle is driving on new, etc., or not recorded in the map data. Also, map-matching does not function correctly when road patterns stored in the map data and the actual road pattern are different due to repair, etc.
Therefore, the map-matching function judges an other road as currently being driven on road if the road is not on the map, and displays the current location mark on it. Later, the current location mark may be repositioned if 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 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.