Map matching method and apparatus for navigation system

• US 20080091347A1
• Filed: 10/16/2006
• Published: 04/17/2008
• Est. Priority Date: 10/16/2006
• Status: Active Grant

• Current Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Original Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Inventors: Tashiro, Eric
• Granted Patent: US 7,603,233 B2
• Time in Patent Office: Days
• US Class Current: 701/210
• CPC Class Codes: G01C 21/30 Map- or contour-matching

Abstract

A map matching method and apparatus for a navigation system estimates a location of the navigation system on a correct road segment when a GPS signal is invalid. The map matching method creates a database of pairs of locations at which the navigation system encountered GPS signal loss and recovery in the first time. The navigation system conducts a map matching processing when the GPS signal is lost in the second time at the recorded location by incorporating various additional factors to match the current position with a correct road segment. The various additional factors, in addition to the measured data by a dead reckoning process, include road class, road accessibility, road angle, proximity to candidate road, etc.

Claims

1. A map matching method for a navigation system, comprising the following steps of:

recording a pair of locations where a GPS signal was lost and recovered in a memory when a user of a navigation system newly encounters GPS signal loss;

comparing a current location of the user with the locations recorded in the memory and retrieving the pair of locations when the user is approaching the location where the GPS signal was previously lost;

selecting one or more candidate routes between the pair of locations retrieved from the memory when the user experiences the GPS signal loss in a second time by extrapolating between the pair of locations;

estimating a route out of the candidate routes which is most likely that the user is taking based on measured data through a dead reckoning process in addition to predetermined factors; and

map matching a current location of the user with a road segment on the estimated route derived from a map database of the navigation system;

wherein the predetermined factors include, in addition to proximity with a road, at least a road class which indicates a type of road.

2. A map matching method for a navigation system as defined in claim 1, further comprising a step of creating a database of pairs of locations where the GPS signal was lost and recovered by repeating the step of recording the pair of locations in the memory every time when the navigation system newly encounters GPS signal loss.

3. A map matching method for a navigation system as defined in claim 2, wherein each location where the GPS signal was lost and the GPS signal was recovered is recorded in the database by longitude and latitude data.

4. A map matching method for a navigation system as defined in claim 2, wherein the database includes data showing a number of times that each pair of locations where the GPS signal was lost and the GPS signal was recovered have been used so far for the map matching.

5. A map matching method for a navigation system as defined in claim 1, wherein the step of recording the pair of locations where the GPS signal was lost and recovered in the memory includes a step of selecting road segments within a predetermined range determined by GPS accuracy.

6. A map matching method for a navigation system as defined in claim 1, wherein the predetermined factors for estimating the route further include a speed range associated with a particular road class.

7. A map matching method for a navigation system as defined in claim 1, wherein the predetermined factors for estimating the route further include accessibility of a road which at least includes distinction whether a particular road is one-way or not.

8. A map matching method for a navigation system as defined in claim 1, wherein the predetermined factors for estimating the route further include an angle of road.

9. A map matching apparatus for a navigation system, comprising:

means for recording a pair of locations where a GPS signal was lost and recovered in a memory when a user of a navigation system newly encounters GPS signal loss;

means for comparing a current location of the user with the locations recorded in the memory and retrieving the pair of locations when the user is approaching the location where the GPS signal was lost previously;

means for selecting one or more candidate routes between the location where the GPS signal was lost and the location where the GPS signal was recovered retrieved from the memory when the user experiences the GPS signal loss in a second time;

means for estimating a route out of the candidate routes which is most likely that the user is taking based on measured data through a dead reckoning process in addition to predetermined factors; and

means for map matching a current location of the user with a road segment on the estimated route derived from a map database of the navigation system;

wherein the predetermined factors include, in addition to proximity to a road, at least a road class which indicates a type of road.

10. A map matching apparatus for a navigation system as defined in claim 9, further comprising means for creating a database of pairs of locations where the GPS signal was lost and recovered by repeating a process recording the pair of locations in the memory every time when the navigation system newly encounters GPS signal loss.

11. A map matching apparatus for a navigation system as defined in claim 10, wherein each location where the GPS signal was lost and the GPS signal was recovered is recorded in the database by longitude and latitude data.

12. A map matching apparatus for a navigation system as defined in claim 10, wherein the database includes data showing a number of times that each pair of locations where the GPS signal was lost and the GPS signal was recovered have been used for the map matching.

13. A map matching apparatus for a navigation system as defined in claim 9, wherein the means for recording the pair of locations where the GPS signal was lost and recovered in the memory includes means for selecting road segments within a predetermined range determined by GPS accuracy.

14. A map matching apparatus for a navigation system as defined in claim 9, wherein the predetermined factors for estimating the route further include a speed range associated with a particular road class.

15. A map matching apparatus for a navigation system as defined in claim 9, wherein the predetermined factors for estimating the route further include accessibility of a road which includes distinction whether a particular road is one-way or not.

16. A map matching apparatus for a navigation system as defined in claim 9, wherein the predetermined factors for estimating the route further include an angle of road.