Method and system for GPS and WAAS carrier phase measurements for relative positioning

• US 6,469,663 B1
• Filed: 10/24/2000
• Issued: 10/22/2002
• Est. Priority Date: 03/21/2000
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: CSI Wireless Incorporated
• Inventors: Whitehead, Michael L., Feller, Walter
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/695,530
• Time in Patent Office: 728 Days
• Field of Search: 342/357.03, 342/357.09, 342/357.1, 701/215
• US Class Current: 342/357.31
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 19/51 Relative positioning

Abstract

A technique of accurately determining the relative position between two points using carrier phase information from receivers capable of making code and carrier phase measurements on signals transmitted from GPS satellites as well as signals transmitted from WAAS, EGNOS, MSAS or other Wide Area Augmentation System satellites (hereafter referred to simply as WAAS satellites). These signals are processed by a receiving system to determine relative position, for the purpose of surveying or otherwise, with the accuracy of carrier phase measurements being obtained. Signal processing similar to that used in existing GPS carrier phase based relative positioning receivers is used with WAAS signals as well. Benefits include faster and more reliable integer ambiguity resolution, protection from cycle slips and loss of sufficient satellites, and possibility of extending the operating range by allowing increased separation of reference and base receivers by incorporating ionospheric models provided by WAAS.

Claims

1. A receiver system, comprising:

a first receiver for determining a first plurality of global positioning system (GPS) carrier phases from a first plurality of GPS signals, determining a Wide Area Augmentation (WAAS) carrier phase from at least one WAAS satellite signal, and issuing information for said first plurality of GPS carrier phases and said WAAS carrier phase in a first output signal;

a second receiver for determining a second plurality of GPS carrier phases from a second plurality of GPS signals and a second WAAS carrier phase from said at least one WAAS satellite signal, and issuing information for said second plurality of GPS carrier phases and said WAAS carrier phase in a second output signal;

a device for receiving said first output signal and said second output signal and computing a location vector between a geographical location of said first receiver and a geographical location of said second receiver based upon differences between said first plurality of GPS carrier phases and said second plurality of GPS carrier phases and said first WAAS carrier phase and said second WAAS carrier phase;

one or more links for communicating said first output signal from said first receiver to said device and said second output signal from said second receiver to said device.

2. The receiver system of claim 1, further including:

said second receiver, which may be a plurality of receivers;

said second plurality of GPS carrier phases, which may be a plurality;

said second plurality of GPS signals, which may be a plurality;

said second WAAS carrier phase, which may be a plurality; and

said at least one WAAS satellite signal, which may be a plurality.

3. The receiver system of claim 1, wherein said receiving and said computing may be distributed between said device, said first receiver, and said second receiver.

4. The receiver system of claim 1, wherein said device may be integral with said second receiver.

5. The receiver system of claim 1, wherein said device may be integral with said first receiver.

6. The receiver system of claim 1, wherein said second plurality of satellites may be identical to said first plurality of satellites.

7. The system of claim 1, wherein said first plurality of satellites and said second plurality of satellites include GPS, GLONASS, WAAS, EGNOS, MAST, AND GNSS satellites.

8. A method of determining a relative position between at least two locations, the method comprising:

receiving at a first location a first plurality of satellite signals from a first plurality of satellites including at least one WAAS satellite and receiving at a second location a second plurality of satellite signals from a second plurality of satellites including said at least one WAAS satellite over a common time period;

processing said first plurality of satellite signals from each satellite of said first plurality of satellites;

processing said second plurality of satellite signals from each satellite of said second plurality of satellites;

calculating a first plurality of pseudoranges from measurements of a first plurality of timing patterns contained within said first plurality of satellite signals;

calculating a second plurality of pseudoranges from measurements of a second plurality of timing patterns contained within said second plurality of satellite signals;

establishing said first location as a reference location and reference position;

computing a plurality of true ranges between said reference location and each satellite of said first plurality of satellites; and

communicating information derived from said computing to said second location in an output signal.

9. The method of claim 8, further comprising:

receiving said output signal at said second location;

determining a plurality of difference terms by forming a difference between each pseudorange of said first plurality of pseudoranges and each corresponding pseudorange of said second plurality of pseudoranges respectively; and

solving equations involving said plurality of difference terms and involving said plurality of true ranges to obtain said relative position of said second location relative to said first location.

10. The method of claim 8, further comprising:

receiving said output signal at said second location;

determining a plurality of correction terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said first plurality of pseudoranges;

adding each correction term of said plurality of correction terms to each corresponding pseudorange of said second plurality of pseudoranges to form a plurality of corrected pseudoranges; and

solving equations involving said plurality of corrected pseudoranges to obtain said relative position of said second location relative to said first location.

11. The method of claim 9, wherein said relative position between at least two locations is determined by double differences of said plurality of difference terms.

12. The method of claim 10, wherein said relative position between at least two locations is determined by double differences of said plurality of corrected pseudoranges.

13. The method of claim 8, wherein said first plurality of satellites and said second plurality of satellites include GPS, GLONASS, WAAS, EGNOS, MSAT and GNSS satellites.

14. The method of claim 8, wherein said first plurality timing patterns are pseudorandom codes.

15. The method of claim 8, wherein said second plurality of timing patterns is pseudorandom codes.

16. The method of claim 8, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes.

17. The method of claim 8, wherein said first plurality of timing patterns are carrier phases.

18. The method of claim 8, wherein said second plurality of timing patterns are carrier phases.

19. The method of claim 8, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes and carrier phases.

20. The method of claim 8, further including:

retrieving a map of ionospheric vertical delays from a WAAS broadcast message;

determining a plurality of pierce points for said first plurality of satellite signals and said second plurality of satellite signals as they intersect an ionospheric shell assumed by said map;

fitting data from said map to said plurality of pierce points and computing slant delays at said plurality of pierce points; and

applying ionospheric delays for satellites seen in common at said at least two locations to reduce errors in said determining relative position.

21. The method of claim 17, further including determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

22. The method of claim 18, further including determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

23. The method of claim 19, further including determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

24. The method of claim 9, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of difference terms.

25. The method of claim 10, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of correction terms.

26. The method of claim 8, wherein said second plurality of satellites may be identical to said first plurality of satellites.

27. The method of claim 9, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said difference terms, yielding ambiguity-free difference terms.

28. The method of claim 10, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said plurality of corrected pseudoranges, yielding ambiguity-free, corrected pseudoranges.

29. A storage medium encoded with a machine-readable computer program code for determining a relative position between at least two locations, said storage medium including instructions for causing a computing system to implement a method comprising:

receiving at a first location a first plurality of satellite signals from a first plurality of satellites including at least one WAAS satellite and receiving at a second location a second plurality of satellite signals from a second plurality of satellites including said at least one WAAS satellite over a common time period;

processing said first plurality of satellite signals from each satellite of said first plurality of satellites;

processing said second plurality of satellite signals from each satellite of said second plurality of satellites;

calculating a first plurality of pseudoranges from measurements of a first plurality of timing patterns contained within said first plurality of satellite signals;

calculating a second plurality of pseudoranges from measurements of a second plurality of timing patterns contained within said second plurality of satellite signals;

establishing said first location as a reference location and reference position;

computing a plurality of true ranges between said reference location and each satellite of said first plurality of satellites; and

communicating information derived from said computing to said second location in an output signal.

30. The storage medium of claim 29, further including instructions for causing a computing system to implement a method comprising:

receiving said output signal at said second location;

determining a plurality of difference terms by forming a difference between each pseudorange of said first plurality of pseudoranges and each corresponding pseudorange of said second plurality of pseudoranges respectively; and

solving equations involving said plurality of difference terms and involving said plurality of true ranges to obtain said relative position of said second location relative to said first location.

31. The storage medium of claim 29, further including instructions for causing a computing system to implement a method comprising:

receiving said output signal at said second location;

determining a plurality of correction terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said first plurality of pseudoranges;

adding each correction term of said plurality of correction terms to each corresponding pseudorange of said second plurality of pseudoranges to form a plurality of corrected pseudoranges; and

solving equations involving said plurality of corrected pseudoranges to obtain said relative position of said second location relative to said first location.

32. The storage medium of claim 30, wherein said relative position between at least two locations is determined by double differences of said plurality of difference terms.

33. The storage medium of claim 31, wherein said relative position between at least two locations is determined by double differences of said plurality of corrected pseudoranges.

34. The storage medium of claim 29, wherein said first plurality of satellites and said second plurality of satellites include GPS, GLONASS, WAAS, EGNOS, MSAT and GNSS satellites.

35. The storage medium of claim 29, wherein said first plurality timing patterns are pseudorandom codes.

36. The storage medium of claim 29, wherein said second plurality of timing patterns is pseudorandom codes.

37. The storage medium of claim 29, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes.

38. The storage medium of claim 29, wherein said first plurality of timing patterns are carrier phases.

39. The storage medium of claim 29, wherein said second plurality of timing patterns are carrier phases.

40. The storage medium of claim 29, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes and carrier phases.

41. The storage medium of claim 29, further including instructions for causing a computing system to implement a method comprising:

retrieving a map of ionospheric vertical delays from a WAAS broadcast message;

determining a plurality of pierce points for said first plurality of satellite signals and said second plurality of satellite signals as they intersect an ionospheric shell assumed by said map;

fitting data from said map to said plurality of pierce points and computing slant delays at said plurality of pierce points; and

applying ionospheric delays for satellites seen in common at said at least two locations to reduce errors in said determining relative position.

42. The storage medium of claim 38, further including instructions for causing a computing system to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

43. The storage medium of claim 39, further including instructions for causing a computing system to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

44. The storage medium of claim 40, further including instructions for causing a computing system to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

45. The storage medium of claim 30, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of difference terms.

46. The storage medium of claim 31, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of correction terms.

47. The storage medium of claim 29, wherein said second plurality of satellites may be identical to said first plurality of satellites.

48. The storage medium of claim 30, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said difference terms, yielding ambiguity-free difference terms.

49. The storage medium of claim 31, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said plurality of corrected pseudoranges, yielding ambiguity-free, corrected pseudoranges.

50. A computer data signal for determining a relative position between at least two locations, said computer data signal comprising code configured to cause a processor to implement a method comprising:

receiving at a first location a first plurality of satellite signals from a first plurality of satellites including at least one WAAS satellite and receiving at a second location a second plurality of satellite signals from a second plurality of satellites including said at least one WAAS satellite over a common time period;

processing said first plurality of satellite signals from each satellite of said first plurality of satellites;

processing said second plurality of satellite signals from each satellite of said second plurality of satellites;

calculating a first plurality of pseudoranges from measurements of a first plurality of timing patterns contained within said first plurality of satellite signals;

calculating a second plurality of pseudoranges from measurements of a second plurality of timing patterns contained within said second plurality of satellite signals;

establishing said first location as a reference location and reference position;

computing a plurality of true ranges between said reference location and each satellite of said first plurality of satellites; and

communicating information derived from said computing to said second location in an output signal.

51. The computer data signal of claim 50, further comprising code configured to cause a processor to implement a method comprising:

receiving said output signal at said second location;

determining a plurality of difference terms by forming a difference between each pseudorange of said first plurality of pseudoranges and each corresponding pseudorange of said second plurality of pseudoranges respectively; and

solving equations involving said plurality of difference terms and involving said plurality of true ranges to obtain said relative position of said second location relative to said first location.

52. The computer data signal of claim 50, further comprising code configured to cause a processor to implement a method comprising:

receiving said output signal at said second location;

determining a plurality of correction terms by forming a difference between each true range of said plurality of true ranges and each corresponding pseudorange of said first plurality of pseudoranges;

adding each correction term of said plurality of correction terms to each corresponding pseudorange of said second plurality of pseudoranges to form a plurality of corrected pseudoranges; and

solving equations involving said plurality of corrected pseudoranges to obtain said relative position of said second location relative to said first location.

53. The computer data signal of claim 51, wherein said relative position between at least two locations is determined by double differences of said plurality of difference terms.

54. The computer data signal of claim 52, wherein said relative position between at least two locations is determined by double differences of said plurality of corrected pseudoranges.

55. The computer data signal of claim 50, wherein said first plurality of satellites and said second plurality of satellites include GPS, GLONASS, WAAS, EGNOS, MSAT and GNSS satellites.

56. The computer data signal of claim 50, wherein said first plurality timing patterns are pseudorandom codes.

57. The computer data signal of claim 50, wherein said second plurality of timing patterns is pseudorandom codes.

58. The computer data signal of claim 50, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes.

59. The computer data signal of claim 50, wherein said first plurality of timing patterns are carrier phases.

60. The computer data signal of claim 50, wherein said second plurality of timing patterns are carrier phases.

61. The computer data signal of claim 50, wherein said first plurality of timing patterns and said second plurality of timing patterns are pseudorandom codes and carrier phases.

62. The computer data signal of claim 50, further including code configured to cause a processor to implement a method comprising:

retrieving a map of ionospheric vertical delays from a WAAS broadcast message;

determining a plurality of pierce points for said first plurality of satellite signals and said second plurality of satellite signals as they intersect an ionospheric shell assumed by said map;

fitting data from said map to said plurality of pierce points and computing slant delays at said plurality of pierce points; and

applying ionospheric delays for satellites seen in common at said at least two locations to reduce errors in said determining relative position.

63. The computer data signal of claim 59, further including code configured to cause a processor to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

64. The computer data signal of claim 60, further including code configured to cause a processor to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

65. The computer data signal of claim 61, further including code configured to cause a processor to implement a method comprising:

determining whether a cycle slip has occurred in measurement of carrier phase from additional carrier phase data available from a WAAS signal.

66. The computer data signal of claim 50, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of difference terms.

67. The computer data signal of claim 52, wherein determination of said relative position between at least two locations is facilitated by information received from an external source possessing additional knowledge of said plurality of correction terms.

68. The computer data signal of claim 50, wherein said second plurality of satellites may be the same as said first plurality of satellites.

69. The computer data signal of claim 51, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said difference terms, yielding ambiguity-free difference terms.

70. The computer data signal of claim 52, wherein carrier phase measurements of a WAAS satellite, which is seen in common to both said first location and said second location are used in to eliminate any integer ambiguity in said plurality of corrected pseudoranges, yielding ambiguity-free, corrected pseudoranges.