Method and system for route calculation in a navigation application

• US 6,678,611 B2
• Filed: 09/27/2002
• Issued: 01/13/2004
• Est. Priority Date: 03/25/1998
• Status: Expired due to Term

• Current Assignee: HERE Global B.V. (Nokia Corporation)
• Original Assignee: Navigation Technologies Corp. (Nokia Corporation)
• Inventors: McDonough, William, Voloshin, Oleg, Wang, Yaoguang, Khavakh, Asta
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US10/259,897
• Publication Number:
  US 20030028319A1
• Time in Patent Office: 473 Days
• Field of Search: 701/209, 701/210
• US Class Current: 701/210
• CPC Class Codes: G01C 21/34 Route searching; Route guidance
• CPC Class Codes: G01C 21/3415 Dynamic re-routing, e.g. recalculating the route when the user deviates from calculated route or after detecting real-time traffic data or accidents
• CPC Class Codes: G01C 21/343 Calculating itineraries, i.e. routes leading from a starting point to a series of categorical destinations using a global route restraint, round trips, touristic trips travelling salesman problem G06Q10/04; optimisation of routes G06Q10/047
• CPC Class Codes: G01C 21/3446 Details of route searching algorithms, e.g. Dijkstra, A*, arc-flags, using precalculated routes
• CPC Class Codes: G01C 21/3492 employing speed data or traffic data, e.g. real-time or historical traffic control systems for road vehicles involving transmission of navigation instructions to the vehicle G08G1/0968

Abstract

A program and method for route calculation for use with a navigation system and used with a map database that represents a road network in a geographic region. A route calculation program is adapted to find at least one solution route between a first location on a road network and a second location on the road network. The route calculation program includes a first search tree associated with the first location and a second search tree associated with the second location. Each search tree is adapted to hold gates. Each of the gates represents a physical position on the road network and a direction from the position to another location along a path on the road network. The route calculation program also includes at least one priority queue associated with one of the search trees. The priority queue assigns a priority to one of the gates in the associated search tree based upon an evaluation using a search algorithm. The gate identified as having a higher priority than any other gate in its respective search tree is expanded to determine one or more successor gates thereof. Each of these successor gates so formed is compared to the gates in the other search tree. The process of growing at least one of the search trees by expanding the gate in the search tree that has a higher priority than any other gate in the search tree is continued until a gate in one search tree corresponds to at least one gate in the other search tree.

Claims

1. A method of performing a rerouting function using a navigation system having a route calculation program that uses a map database that includes road segment records that represent portions of roads in a road network in a geographic region, comprising the steps of:

after calculating a solution route from a first location in said geographic region to a second location in said geographic region, wherein said solution route is represented by a list of road segment records, storing an inbound search tree formed of a plurality of gates, wherein each gate represents a physical location on said road network and an accessible direction relative to said physical location, and wherein said plurality of gates in said inbound search tree represent segments of roads of said road network from which said second location is accessible,

upon said navigation system having departed from the solution route, providing data representing a physical location of said navigation system; and

growing said inbound search tree until at least one successor gate of the plurality of gates in said inbound search tree corresponds to said data representing the physical location of said navigation system.

2. The method of claim 1 wherein each gate identifies an associated segment of a road by referring to a segment database ID.

3. The method of claim 1 wherein each gate identifies an associated segment of a road with a pointer.

4. The method of claim 1 wherein, in each gate, the accessible direction is reverse from a direction of vehicle travel.

5. The method of claim 1 wherein each gate also includes a reference to a predecessor gate.

6. The method of claim 1 further comprising:

after calculating the solution route from the first location to the second location, augmenting the inbound search tree by adding thereto that portion of an outbound search tree that formed part of the solution route.

7. The method of claim 6 further comprising:

maintaining in a memory of the navigation system the inbound search tree as augmented with the portion of the outbound search tree.

8. The method of claim 1 further comprising:

providing a user of the navigation system with guidance for following a route to the second location from the physical location of the navigation system.

9. The method of claim 1 further comprising:

prompting a user of the navigation system to indicate whether a new route should be calculated upon detection that the navigation system departed from the solution route.

10. A method of providing an alternative route using a navigation system having a route calculation program that uses a map database that includes road segment records that represent portions of roads in a road network in a geographic region, wherein said alternative route has minimal overlap with an original solution route, the method comprising the steps of:

after calculating the original solution route between a first location in said geographic region and a second location in said geographic region, wherein said solution route comprises a list of road segment records that was obtained by forming at least one search tree formed of a plurality of gates, wherein each gate represents a physical location on said road network and an accessible direction relative to said physical location, incrementing a weighting associated with each of said gates in said at least one search tree that corresponds to said list of road segment records that comprise said solution route, wherein a lower weighting favors inclusion of said gate relative to a higher weighting;

growing the search tree by expanding gates to form successor gates; and

evaluating which of said successor gates to select for further expansion using said incremented weighting until the alternate route is determined.

11. The method of claim 10 wherein the weighting indicates traffic conditions.

12. The method of claim 10 wherein each gate identifies an associated segment of a road by referring to a segment database ID.

13. The method of claim 10 wherein each gate identifies an associated segment of a road with a pointer.

14. The method of claim 10 wherein each gate also includes a reference to a predecessor gate.

15. The method of claim 10 wherein the weighting is provided to the navigation system by wireless transmission.

16. The method of claim 10 wherein the weighting is provided to the navigation system from a traffic monitoring service.