Relative GPS positioning using a single GPS receiver with internally generated differential correction terms

• US 6,397,147 B1
• Filed: 10/24/2000
• Issued: 05/28/2002
• Est. Priority Date: 06/06/2000
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: CSI Wireless Incorporated
• Inventors: Whitehead, Michael L.
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Tran, Dalena
• Application Number:
  US09/695,608
• Time in Patent Office: 581 Days
• Field of Search: 701/213,207,214,225,215 342/357.02,357.06,357.08,357.03,357.11,356
• US Class Current: 701/213
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/51 Relative positioning

Abstract

A technique of accurately determining the relative position between two points, in real-time, using a single GPS receiver that makes measurements of signals transmitted from GPS satellites. A technique is applied where differential correction terms are computed as a location at an instant of time, and then applied to further times, after applying atmospheric delay adjustments, so that the position of the GPS receiver is determined accurately relative to the position at the original instant of time.

Claims

1. A method for determining location coordinates relative to a reference location, the method comprising:

receiving a plurality of satellite signals with a receiver, said plurality of satellite signals transmitted from a plurality of satellites;

determining a plurality of pseudoranges to said plurality of satellites by measuring timing patterns contained within said plurality of satellite signals;

establishing said reference location at a known location;

determining a plurality of true ranges between said reference location and each satellites of said plurality of satellites;

determining a plurality of error terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said plurality of pseudoranges, respectively;

calculating a plurality of correction terms by mathematically removing predictable inaccuracies from said plurality of error terms;

retaining said plurality of correction terms;

combining said correction terms with subsequent measured pseudoranges when computing feature locations of said receiver; and

wherein said receiver acts first as a reference receiver;

computing said plurality of correction terms, and then as a remote receiver;

applying said plurality of correction terms when computing its location.

2. The method of claim 1, wherein said receiver processes information from GPS, GLONASS, WAAS, EGNOS, MSAT or other GNSS satellites.

3. The method of claim 1,further comprising calculating a clock adjustment and a range adjustment if satellite parameters change.

4. The method of claim 1, further comprising applying a clock correction if a new satellite is encountered.

5. The method of claim 1, wherein said receiver periodically calibrates said plurality of correction terms by returning to a known location.

6. The method of claim 1, wherein said plurality of correction terms is retained collectively as a model.

7. The method of claim 6, wherein said plurality of correction terms is retained as an ionospheric delay model.

8. The method of claim 6, further comprising:

adjusting said model to eliminate estimated errors; and

deriving said plurality of correction terms from said adjusting.

9. The method of claim 6, wherein an ionosphere model is uploaded to said receiver periodically.

10. The method of claim 6, wherein an ionospheric error term is estimated.

11. The method of claim 1, wherein a weighting scheme is used to change a relative importance of said plurality of correction terms when mathematically solving for a location of said receiver.

12. The method of claim 1, wherein said receiver is coupled to aiding devices comprising altimeters, inertial measurement units, compasses, gyroscopes, wheel rotation sensors, velocity sensors, or accelerometers.

13. The method of claim 12, wherein said aiding devices are utilized to augment said calculating of said plurality of correction terms.

14. The method of claim 12, wherein said receiver re-calibrates its position by knowing a partial set of location coordinates.

15. The method of claim 1, wherein said receiver re-calibrates its position using a form of dead reckoning.

16. The method of claim 1, wherein said predictable inaccuracies are determined from mathematical models.

17. The method of claim 1, wherein said predictable inaccuracies are measurements facilitating determination of said plurality of error terms.

18. The method of claim 1, wherein said predictable inaccuracies are received from an external source having knowledge of said plurality of error terms.

19. The method of claim 1, wherein said retaining may include computer memory, disk, an attachment to said receiver, or other mediums of retention.

20. A storage medium encoded with a machine-readable computer program code for determining location coordinates relative to a reference location, said storage medium including instructions for causing a computing system to implement a method comprising:

receiving a plurality of satellite signals with a receiver, said plurality of satellite signals transmitted from a plurality of satellites;

determining a plurality of pseudoranges to said plurality of satellites by measuring timing patterns contained within said plurality of satellite signals;

establishing said reference location at a known location;

determining a plurality of true ranges between said reference location and each satellites of said plurality of satellites;

determining a plurality of error terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said plurality of pseudoranges, respectively;

calculating a plurality of correction teems by mathematically removing predictable inaccuracies from said plurality of error terms;

retaining said plurality of correction terms;

combining said correction terms with subsequent measured pseudoranges when computing future locations of said receiver; and

wherein said receiver acts first as a reference receiver;

computing said plurality of correction terms, and then as a remote receiver;

applying said plurality of correction terms when computing its location.

21. The storage medium of claim 20, wherein said receiver processes information from GPS, GLONASS, WAAS, EGNOS, MSAT or other GNSS satellites.

22. The storage medium of claim 20, further including instructions for causing a computing system to implement a method comprising:

calculating a clock adjustment and a range adjustment if satellite parameters change.

23. The storage medium of claim 20, further including instructions for causing a computing system to implement a method comprising:

applying a clock correction if a new satellite is encountered.

24. The storage medium of claim 20, wherein said receiver periodically calibrates said plurality of correction terms by returning to a known location.

25. The storage medium of claim 20, wherein said plurality of correction terms is retained collectively as a model.

26. The storage medium of claim 25, wherein said plurality of correction terms is retained as an ionospheric delay model.

27. The storage medium of claim 25, further including instructions for causing a computing system to implement a method comprising:

adjusting said model to eliminate estimated errors; and

deriving said plurality of correction terms from said adjusting.

28. The storage medium of claim 25, wherein an ionosphere model is uploaded to said receiver periodically.

29. The storage medium of claim 25, wherein an ionospheric error term is estimated.

30. The storage medium of claim 20, wherein a weighting scheme is used to change a relative importance of said plurality of correction terms when mathematically solving for a location of said receiver.

31. The storage medium of claim 20, wherein said receiver is coupled to aiding devices comprising altimeters, inertial measurement units, compasses, gyroscopes, wheel rotation sensors, velocity sensors, or accelerometers.

32. The storage medium of claim 31, wherein said aiding devices are utilized to augment said calculating of said plurality of correction terms.

33. The storage medium of claim 31, wherein said receiver re-calibrates its position by knowing a partial set of location coordinates.

34. The storage medium of claim 20, wherein said receiver re-calibrates its position using a form of dead reckoning.

35. The storage medium of claim 20, wherein said predictable inaccuracies are determined from mathematical models.

36. The storage medium of claim 20, wherein said predictable inaccuracies are measurements facilitating determination of said plurality of error terms.

37. The storage medium of claim 20, wherein said predictable inaccuracies are received from an external source having knowledge of said plurality of error terms.

38. The storage medium of claim 20, wherein said retaining may include computer memory, disk, an attachment to said receiver, or other mediums of retention.

39. A computer data signal for determining location coordinates relative to a reference location, said computer data signal comprising code configured to cause a processor to implement a method comprising:

receiving a plurality of satellite signals with a receiver, said plurality of satellite signals transmitted from a plurality of satellites;

determining a plurality of pseudoranges to said plurality of satellites by measuring timing patterns contained within said plurality of satellite signals;

establishing said reference location at a known location;

determining a plurality of true ranges between said reference location and each satellites of said plurality of satellites;

determining a plurality of error terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said plurality of pseudoranges, respectively;

calculating a plurality of correction terms by mathematically removing predictable inaccuracies from said plurality of error terms;

retaining said plurality of correction terms;

combining said correction terms with subsequent measured pseudoranges when computing future locations of said receiver; and

wherein said receiver acts first as a reference receiver;

computing said plurality of correction terms, and then as a remote receiver;

applying said plurality of correction terms when computing its location.

40. The computer data signal of claim 39, wherein said receiver processes information from GPS, GLONASS, WAAS, EGNOS, MSAT or other GNSS satellites.

41. The computer data signal of claim 39, further comprising code configured to cause a processor to implement a method comprising:

calculating a clock adjustment and a range adjustment if satellite parameters change.

42. The computer data signal of claim 39, further comprising code configured to cause a processor to implement a method comprising:

applying a clock correction if a new satellite is encountered.

43. The computer data signal of claim 39, wherein said receiver periodically re-calibrates said plurality of correction terms by returning to a known location.

44. The computer data signal of claim 39, wherein said plurality of correction terms is computer data signaled collectively as a model.

45. The computer data signal of claim 44, wherein said plurality of correction terms is retained as an ionospheric delay model.

46. The computer data signal of claim 44, further comprising code configured to cause a processor to implement a method comprising:

adjusting said model to eliminate estimated errors; and

deriving said plurality of correction terms from said adjusting.

47. The computer data signal of claim 44, wherein an ionosphere model is uploaded to said receiver periodically.

48. The computer data signal of claim 44, wherein an ionospheric error term is estimated.

49. The computer data signal of claim 39, wherein a weighting scheme is used to change a relative importance of said plurality of correction terms when mathematically solving for a location of said receiver.

50. The computer data signal of claim 39, wherein said receiver is coupled to aiding devices comprising altimeters, inertial measurement units, compasses, gyroscopes, wheel rotation sensors, velocity sensors, or accelerometers.

51. The computer data signal of claim 50, wherein said aiding devices are utilized to augment said calculating of said plurality of correction terms.

52. The computer data signal of claim 50, wherein said receiver re-calibrates its position by knowing a partial set of location coordinates.

53. The computer data signal of claim 39, wherein said receiver re-calibrates its position using a form of dead reckoning.

54. The computer data signal of claim 39, wherein said predictable inaccuracies are determined from mathematical models.

55. The computer data signal of claim 39, wherein said predictable inaccuracies are measurements facilitating determination of said plurality of error terms.

56. The computer data signal of claim 39, wherein said predictable inaccuracies are received from an external source having knowledge of said plurality of error terms.

57. The computer data signal of claim 39, wherein said retaining may include computer memory, disk, an attachment to said receiver, or other mediums of retention.