GEOFENCING AND ROUTE ADHERENCE IN GLOBAL POSITIONING SYSTEM WITH SIGNALS FROM FEWER THAN THREE SATELLITES

• US 20080238769A1
• Filed: 03/28/2007
• Published: 10/02/2008
• Est. Priority Date: 03/28/2007
• Status: Active Grant

• Current Assignee: 2201028 Ontario Incorporated
• Original Assignee: 2201028 Ontario Incorporated
• Inventors: Verechtchiagine, Dimitri
• Granted Patent: US 7,492,315 B2
• Time in Patent Office: Days
• US Class Current: 342/357.12
• CPC Class Codes: G01S 19/42 Determining position

Abstract

When a global positioning system receiver receives signals from too few satellites to determine its position unambiguously, the receiver determines a solution surface as a set of possible locations determined from the signals received from the satellites. It then determines a minimum possible distance from a base location to that solution surface. If the base location is a geofence anchor, the receiver can determine whether a geofence crossing event has happened. If the base location is on a route, the receiver can determine whether it is following the route. A receiver with an ordinary clock can do so with signals from two satellites; a receiver with an extremely accurate clock can do so with a signal from one satellite.

Claims

1. A method for determining a minimum distance from a global positioning system receiver to a reference location, the method comprising:

(a) receiving at least one global positioning system signal from no more than two global positioning system satellites in the global positioning system receiver;

(b) determining, from the at least one global positioning system signal received in step (a), a set of possible locations at which the global positioning system can be located; and

(c) determining a minimum distance from the set of possible locations to the reference location as the minimum distance from the global positioning system receiver to the reference location.

2. The method of claim 1, wherein, in step (a), said at least one global positioning system signal is received from only one said global positioning system satellite, and wherein said global positioning system receiver comprises a clock which is substantially free of clock bias.

3. The method of claim 1, wherein, in step (a), said at least one global positioning system signal is received from two said global positioning system satellites.

4. The method of claim 3, wherein step (b) comprises determining a solution surface comprising the set of possible locations.

5. The method of claim 4, wherein step (c) comprises determining a minimum distance from the solution surface to the reference location.

6. The method of claim 4, wherein the global positioning system receiver is assumed to have a location constraint, and wherein the set of possible locations is determined from the solution surface and the location constraint.

7. The method of claim 6, wherein the location constraint is that the global positioning system receiver is assumed to be on a constraint surface, and wherein the set of possible locations is determined from a intersection of the constraint surface and the solution surface.

8. The method of claim 7, wherein the constraint surface is a horizontal plane.

9. The method of claim 1, wherein the reference location is a previous location of the global positioning system receiver.

10. The method of claim 1, wherein the reference location is determined from a previously determined solution surface.

11. The method of claim 1, wherein the reference location is a geofence anchor location.

12. The method of claim 11, wherein the geofence anchor location has a corresponding geofence radius, and further comprising comparing the minimum distance to the geofence radius to determine whether a geofence crossing even has taken place.

13. The method of claim 1, wherein the reference location is on a route, and further comprising using the minimum distance to determine whether the global positioning system receiver is following the route.

14. The method of claim 13, wherein the route is modeled as a plurality of line segments, and wherein the minimum distance is calculated to each of the line segments.

15. A global positioning system receiver for determining a minimum distance to a reference location, the global positioning system receiver comprising:

an antenna for receiving at least one global positioning system signal from no more than two global positioning system satellites; and

a processor, in communication with the antenna, for determining, from the at least one global positioning system signal received by the antenna, a set of possible locations at which the global positioning system can be located; and

for determining a minimum distance from the set of possible locations to the reference location as the minimum distance from the global positioning system receiver to the reference location.

16. The global positioning system receiver of claim 15, wherein said at least one global positioning system signal is received from only one said global positioning system satellite, and wherein said global positioning system receiver further comprises a clock which is substantially free of clock bias.

17. The global positioning system receiver of claim 15, wherein said at least one global positioning system signal is received from two said global positioning system satellites.

18. The global positioning system receiver of claim 17, wherein the processor determines a solution surface comprising the set of possible locations.

19. The global positioning system receiver of claim 18, wherein the processor determines a minimum distance from the solution surface to the reference location.

20. The global positioning system receiver of claim 18, wherein the global positioning system receiver is assumed to have a location constraint, and wherein the set of possible locations is determined from the solution surface and the location constraint.

21. The global positioning system receiver of claim 20, wherein the location constraint is that the global positioning system receiver is assumed to be on a constraint surface, and wherein the set of possible locations is determined from a intersection of the constraint surface and the solution surface.

22. The global positioning system receiver of claim 21, wherein the constraint surface is a horizontal plane.

23. The global positioning system receiver of claim 15, wherein the reference location is a previous location of the global positioning system receiver.

24. The global positioning system receiver of claim 15, wherein the reference location is determined from a previously determined solution surface.

25. The global positioning system receiver of claim 15, wherein the reference location is a geofence anchor location.

26. The global positioning system receiver of claim 25, wherein the geofence anchor location has a corresponding geofence radius, and further comprising comparing the minimum distance to the geofence radius to determine whether a geofence crossing even has taken place.

27. The global positioning system receiver of claim 15, wherein the reference location is on a route, and further comprising using the minimum distance to determine whether the global positioning system receiver is following the route.

28. The global positioning system receiver of claim 27, wherein the route is modeled as a plurality of line segments, and wherein the minimum distance is calculated to each of the line segments.

29. An article of manufacture for permitting a global positioning system receiver to determine a minimum distance from a global positioning system receiver to a reference location, the article of manufacture comprising:

a computer-readable storage medium; and

code stored in the computer-readable storage medium, the code, when executed in a processor of the global positioning system receiver, controlling the global positioning system receiver for;

(a) receiving at least one global positioning system signal from no more than two global positioning system satellites in the global positioning system receiver;

(b) determining, from the at least one global positioning system signal received in step (a), a set of possible locations at which the global positioning system can be located; and

(c) determining a minimum distance from the set of possible locations to the reference location as the minimum distance from the global positioning system receiver to the reference location.

30. The article of manufacture of claim 29, wherein, in step (a), said at least one global positioning system signal is received from only one said global positioning system satellite, and wherein said global positioning system receiver comprises a clock which is substantially free of clock bias.

31. The article of manufacture of claim 29, wherein, in step (a), said at least one global positioning system signal is received from two said global positioning system satellites.

32. The article of manufacture of claim 29, wherein step (b) comprises determining a solution surface comprising the set of possible locations.

33. The article of manufacture of claim 32 wherein step (c) comprises determining a minimum distance from the solution surface to the reference location.

34. The article of manufacture of claim 32, wherein the global positioning system receiver is assumed to have a location constraint, and wherein the set of possible locations is determined from the solution surface and the location constraint.

35. The article of manufacture of claim 34, wherein the location constraint is that the global positioning system receiver is assumed to be on a constraint surface, and wherein the set of possible locations is determined from a intersection of the constraint surface and the solution surface.

36. The article of manufacture of claim 35, wherein the constraint surface is a horizontal plane.

37. The article of manufacture of claim 29, wherein the reference location is a previous location of the global positioning system receiver.

38. The article of manufacture of claim 29, wherein the reference location is determined from a previously determined solution surface.

39. The article of manufacture of claim 29, wherein the reference location is a geofence anchor location.

40. The article of manufacture of claim 39, wherein the geofence anchor location has a corresponding geofence radius, and further comprising comparing the minimum distance to the geofence radius to determine whether a geofence crossing even has taken place.

41. The article of manufacture of claim 29, wherein the reference location is on a route, and further comprising using the minimum distance to determine whether the global positioning system receiver is following the route.

42. The article of manufacture of claim 41, wherein the route is modeled as a plurality of line segments, and wherein the minimum distance is calculated to each of the line segments.