Route guidance on/off-route state filter

[54] ROUTE GUIDANCE ON/OFF-ROUTE STATE FILTER

[75] Inventor: Peter Snider, San Carlos, Calif.

[73] Assignee: Zexel Corporation, Japan

[21] Appl. No.: 884,749

[22] Filed: May 15,1992

[51] Int. Cl.s G06F 15/50

[52] U.S. CI 364/449; 73/178 R;

340/990; 342/450; 364/450

[58] Field of Search 364/443, 444, 445, 446,

364/447, 448, 449, 450, 453, 454, 424.02; 340/988, 989, 990, 995; 342/450, 451, 457;

73/178 R

[56] References Cited

U.S. PATENT DOCUMENTS

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OTHER PUBLICATIONS

R. L. French, "Map Matching Origins Approaches and Applications," Rober L. French & Associates, 3815 Lisbon St., Suite 201, Fort Worth, Tex., 76107, USA, pp. 91-116, No date.

Primary Examiner—Thomas G. Black

Assistant Examiner—Collin W. Park

Attorney, Agent, or Firm—Townsend and Townsend

Khourie and Crew

[57] ABSTRACT

The invention provides a route state filter 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 to a database 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, checks their validity and applies a filter to remove less likely possibilities. A current position is then selected from the remaining possibilities. An ON/OFF ROUTE status of the vehicle is determined by comparing the selected position with the selected route information in the database. 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 instructional information such as maneuvers, distances, and warnings are communicated to the driver.

23 Claims, 12 Drawing Sheets