Bowing coefficient representation of curvature of geographic features

• US 20020128752A1
• Filed: 01/30/2001
• Published: 09/12/2002
• Est. Priority Date: 01/30/2001
• Status: Active Grant

• Current Assignee: HERE Global B.V. (HERE Holding Corporation)
• Original Assignee: Navteq North America LLC (HERE Holding Corporation)
• Inventors: Joshi, Rajashri
• Granted Patent: US 6,681,177 B2
• Time in Patent Office: Days
• US Class Current: 701/1
• 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 how much a road curves comprising:

selecting two points along the road; and

comparing an approximation of a distance along the road between the two points to a straight-line distance between the two points;

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

2. The method of claim 1 further comprising:

using said indication of how much the road curves to adjust a speed of a 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 step of comparing is performed using shape point data that represent geographic coordinates at locations along the roads.

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

6. A method of representing road geometry comprising:

at selected locations along a road, determining a bowing coefficient, wherein the bowing coefficient at each of said selected locations corresponds to a comparison between an approximation of a distance along the road between two points on the road on either side of the selected location and a straight-line distance between the two points; and

using the bowing coefficient as an indication of curvature of said road between said two points.

7. The method of claim 6 further comprising:

storing data indicating said bowing coefficient in a geographic database that represents said road.

8. A method of operating a vehicle along roads comprising:

with a software application in said vehicle, accessing a database containing data that represent said roads;

determining a location of said vehicle with respect to the roads as represented by said database; and

using data that indicate a bowing coefficient at each of a plurality of locations along said roads to adjust operation of said vehicle.

9. The method of claim 8 wherein a speed at which said vehicle is moving is reduced as said vehicle approaches a portion of said roads at which said bowing coefficient is relatively higher.

10. The method of claim 8 wherein a speed at which said vehicle is moving is increased as said vehicle approaches a portion of said roads at which said bowing coefficient is relatively lower.

11. A method of forming a geographic database comprising:

comparing an approximation of a distance along a road segment between two points to a straight-line distance between said two points; and

storing in said geographic database a result of said comparing as an indication of curvature of said road segment between said two points.

12. A geographic database formed according to the process of claim 11.

15. The method of claim 14 wherein said computing step is performed using data contained in a geographic database located in said vehicle.

13. A method of operating a vehicle along roads comprising:

relating a position of said vehicle on a road to a data representation of the road contained in a geographic database,

wherein the data representation of the road includes an indication of curvature at locations along the road, and

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

adjusting operation of the vehicle based on the indication of curvature corresponding to said position of said vehicle.

14. A method of operating a vehicle along roads comprising:

with a software application in said vehicle, computing a relationship between a distance between two points along a road and a straight-line distance between said two points;

determining a location of said vehicle with respect to said road; and

adjusting operation of said vehicle using said computed relationship.

16. A method of operation for an application in a vehicle comprising:

accessing a geographic database that contains data that represent roads upon which the vehicle is traveling;

determining a position of said vehicle with respect to said data that represent roads upon which the vehicle is traveling; and

using data that represent bowing coefficients at locations along said road to adjust operation of said vehicle.