| 摘要 |
The invention provides a route state filter (74) for a vehicle route guidance system for improved tracking of vehicle position with respect to a preselected route. A set of position possibilities are derived by comparing a measured vehicle position (28) to a data-base (30) containing data representing a map of roads, the possibilities corresponding to possible positions on the roads within an error region around the measured position. A route guidance module receives the position possibilities (70), checks their validity (72) and applies a filter to remove less likely possibilities (74). A current position is then selected from the remaining possibilities (76). An ON/ OFF ROUTE status Or the vehicle is determined by comparing the selected position with the selected route information in the database (35, 78). A distance-based filter is utilized to provide improved continuity in the route status determination. The route status is then used to set the system operating mode, and warnings are communicated to the driver (32, 86).
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