Bowing coefficient representation of curvature of geographic features

• US 6,862,523 B2
• Filed: 11/14/2003
• Issued: 03/01/2005
• Est. Priority Date: 01/30/2001
• Status: Expired due to Term

• Current Assignee: HERE Global B.V. (Nokia Corporation)
• Original Assignee: Navteq North America LLC (Nokia Corporation)
• Inventors: Joshi, Rajashri
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US10/714,131
• Publication Number:
  US 20040107047A1
• Time in Patent Office: 473 Days
• Field of Search: 701/208, 701/25, 701/207, 701/26, 340/988, 702/157, 702/155
• US Class Current: 701/208
• CPC Class Codes: G01C 21/3819 Road shape data, e.g. outline of a route
• CPC Class Codes: G09B 29/003 Maps

Abstract

The degree to which a linearly extending feature, such as a road, curves is indicated using a bowing coefficient. The bowing coefficient at a given location along a linearly extending feature is determined by comparing the distance along the feature between two points on either side of the given location (or an approximation of the distance) to a straight-line distance between these same two points. Bowing coefficient data can be used by various vehicle systems that require information about the curvature of linearly extending features, such as roads upon which the vehicle is traveling.

Claims

1. A method of representing road geometry comprising:

determining an arc length between two points along a road;

determining a chord length between said points along the road; and

comparing said arc length to said chord length;

whereby a result of said comparing is an indication of how much the road curves between said two points.

2. The method of claim 1 further comprising:

using said indication of how much the road curves to adjust a speed of vehicle.

3. The method of claim 1 further comprising:

storing said indication of how much the road curves in a geographic database.

4. The method of claim 1 wherein said determining steps are performed using shape point data that represent geographic coordinates at locations along the road.

5. The method of claim 1 wherein said step of comparing is performed by an application in a vehicle.

6. The method of claim 5 wherein said step of comparing is performed using data contained in a geographic database located in said vehicle.

7. The method of claim 1 wherein said step of determining said are length comprising determining an approximation of a distance along the road between said points.

8. The method of claim 1 wherein said step of determining said chord length comprising determining an approximation of a straight-line distance between said points.

9. The method of claim 1 wherein said result of said comparing is a bowing coefficient.

10. A geographic database formed according to the process of claim 1.

11. A geographic database comprising:

a data representation of a plurality of roads in a geographic region;

wherein said data representation includes an indication of curvature along at least one of said roads; and

wherein said indication of curvature includes a comparison between an arc length between paints along the road and a chord length between said points.

12. A method of operating a vehicle along roads using the geographic database of claim 11, comprising:

using said indication of curvature to adjust a speed of a vehicle.

13. The method of operating the vehicle of claim 12 wherein a speed at which said vehicle is moving is reduced as said vehicle approaches a portion of said roads at which said comparison of said arc length and said chord length is relatively higher.

14. The method of operating the vehicle of claim 12 wherein a speed at which said vehicle is moving is increased as said vehicle approaches a portion of said roads at which said comparison of said arc length and said chord length is relatively lower.

15. The geographic database of claim 11 wherein said arc length is an approximation of a distance along the road between said points.

16. The geographic database of claim 11 where said chord length is an approximation of a straight-line distance between said points.

17. The geographic database of claim 11 where said comparison between said arc length and said chord length is a bowing coefficient.

18. A method of determining how much a road curves comprising:

determining an approximation of an arc length between two points along the road;

determining an approximation of a chord length between said points; and

comparing said arc length to said chord length, wherein a result of said comparing is an indication of how much the road curves between said points.

19. The method of claim 18 wherein said steps determining are performed using shape point data that represent geographic coordinates along the roads.