Conveying orbit information via ambiguous position information

• US 7,737,888 B2
• Filed: 01/14/2008
• Issued: 06/15/2010
• Est. Priority Date: 01/14/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Remondi, Benjamin William
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US12/008,893
• Publication Number:
  US 20090179792A1
• Time in Patent Office: 883 Days
• Field of Search: 342/357.09, 342/357.02
• US Class Current: 342/357.45
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]

Abstract

In a method of conveying information regarding an orbit used at a Global Navigation Satellite System (GNSS) base station to a GNSS receiver, a satellite position is determined for a particular time from an orbit of a GNSS satellite. An ambiguity value is extracted from the satellite position. The ambiguity value is extracted based upon a satellite position determination margin of error of a GNSS receiver. The ambiguity value is encoded into an encoded ambiguity value which is assembled into a message. The message also includes a time tag representing the particular time. The message is transmitted from the GNSS base station. The encoded ambiguity value and the time tag convey information regarding the orbit to a GNSS receiver in receipt of the message.

Claims

1. A method of conveying information regarding an orbit used at a Global Navigation Satellite System (GNSS) base station to a GNSS receiver, said method comprising:

determining a satellite position for a particular time from an orbit of a GNSS satellite;

extracting an ambiguity value from said satellite position, said extracting based upon a satellite position determination margin of error of a GNSS receiver;

encoding said ambiguity value into an encoded ambiguity value;

assembling a message including said encoded ambiguity value and a time tag representing said time; and

transmitting said message from said GNSS base station, whereby said encoded ambiguity value and said time tag convey information regarding said orbit to a GNSS receiver in receipt of said message.

2. The method as recited in claim 1, wherein said resolving an ambiguity value from said satellite position further comprises:

resolving an ambiguity window at least as large as a maximum satellite position determination margin of error of said GNSS receiver; and

using said ambiguity window to resolve said ambiguity value.

3. The method as recited in claim 2, further comprising:

including an additional margin of safety in said ambiguity window such that said ambiguity window is larger than a maximum satellite position determination margin of error of said GNSS receiver.

4. The method as recited in claim 1, wherein said encoding said ambiguity value into an encoded ambiguity comprises:

encoding said ambiguity value into said encoded ambiguity value such that a recipient GNSS receiver is enabled to recreate an approximation of a coordinate of said satellite position by combining a decoded ambiguity value and an ambiguous portion of a second satellite position generated locally at said GNSS receiver.

5. The method as recited in claim 1, wherein said encoding said ambiguity value into an encoded ambiguity value comprises:

encoding information derived from an x, y, or z coordinate of said satellite position into said encoded ambiguity value.

6. The method as recited in claim 1, wherein said assembling a message including said encoded ambiguity value and a time tag representing said time further comprises:

assembling said message to include refinement information, said refinement information for use in refining positioning and navigation data calculated by a recipient of said message.

7. The method as recited in claim 1, wherein said assembling a message including said encoded ambiguity value and a time tag representing said time further comprises:

assembling said message to include descriptive information regarding said encoded ambiguity value.

8. A Global Navigation Satellite System (GNSS) base station comprising:

an orbit processor configured for executing a GNSS orbit algorithm in association with an orbit of a GNSS satellite and a time, such that a satellite position is determined for said time;

an ambiguity value extractor configured for extracting an ambiguity value from said satellite position based upon a satellite position determination margin of error of a GNSS receiver;

an ambiguity value encoder configured for encoding said ambiguity value as an encoded ambiguity value; and

a message assembler configured for assembling a message comprising said encoded ambiguity value and a time tag representing said time.

9. The GNSS bases station of claim 8, wherein said ambiguity value extractor is configured for extracting said ambiguity value using an ambiguity window at least as large as a maximum satellite position determination margin of error a GNSS receiver intended to receive said message.

10. The GNSS base station of claim 8, wherein said message assembler is further configured for assembling said message to include refinement information generated by said GNSS base station, said refinement information for use in refining positioning and navigation data calculated by said GNSS receiver.

11. The GNSS base station of claim 10, wherein:

said refinement information is selected from the group of refinement information consisting of;

correctors and raw measurable information.

12. A method of synchronizing orbits used at a Global Navigation Satellite System (GNSS) receiver and at a GNSS base station, said method comprising:

receiving a message from said GNSS base station, said message comprising a time tag and an encoded ambiguity value derived from a satellite position of a GNSS satellite, said satellite position calculated by said GNSS base station utilizing a first orbit for said GNSS satellite and a time represented by said time tag;

calculating a second satellite position for said GNSS satellite utilizing said time represented by said time tag and a broadcast orbit received at said GNSS receiver from said GNSS satellite;

resolving a third satellite position for said GNSS satellite using said encoded ambiguity value and an ambiguous portion of said second satellite position; and

determining that orbits used at said GNSS base station and said GNSS receiver are synchronized when said third satellite position and said second satellite position are in agreement.

13. The method as recited in claim 12, wherein said receiving a message from said GNSS base station comprises:

receiving said message, wherein said encoded ambiguity value comprises a value derived from and representing a portion of a coordinate of said satellite position.

14. The method as recited in claim 12, wherein determining that orbits used at said GNSS base station and said GNSS receiver are synchronized when said third satellite position and said second satellite position are in agreement further comprises:

approving refinement information for use in refining positioning and navigation data calculated by said GNSS receiver, said refinement information received from said GNSS base station and associated with said time tag.

15. The method as recited in claim 12, further comprising:

when said second satellite position and said third satellite position are not in agreement, performing a nudging process on said broadcast orbit to achieve a nudged broadcast orbit.

16. The method as recited in claim 15, wherein performing a nudging process on said broadcast orbit to achieve a nudged broadcast orbit comprises:

nudging said broadcast orbit into synchronization with said first orbit.

17. The method as recited in claim 15, wherein performing a nudging process on said broadcast orbit to achieve a nudged broadcast orbit comprises:

nudging said broadcast orbit into synchronization with a slightly damaged version of said first orbit.

18. The method as recited in claim 15, wherein said performing a nudging process on said broadcast orbit to achieve a nudged broadcast orbit further comprises:

using said nudged broadcast orbit in calculating positioning and navigation data calculated by said GNSS receiver.

19. The method as recited in claim 18, wherein said using said nudged broadcast orbit in calculating positioning and navigation data calculated by said GNSS receiver further comprises:

approving refinement information for use in refining said positioning and navigation data calculated by said GNSS receiver, said refinement information received from said GNSS base station and associated with said time tag.

20. The method as recited in claim 15, wherein said nudging said broadcast orbit into synchronization with said first orbit comprises:

employing a linear algebra technique to determine an adjustment to a parameter of said broadcast orbit.

21. The method as recited in claim 20, wherein said employing a linear algebra technique to determine an adjustment to a parameter of said broadcast orbit comprises:

utilizing said linear algebra technique to determine adjustments to broadcast orbit parameters roota, M₀, and I₀ when an absolute value of a z-coordinate of said third satellite position is greater than one earth radius; and

utilizing said linear algebra technique to determine adjustments to broadcast orbit parameters roota, M₀, and Ω

₀ when said absolute value of said z-coordinate of said third satellite position is not greater than one earth radius.

22. A Global Navigation Satellite System (GNSS) receiver comprising:

a message receiver configured for receiving a message broadcast from a GNSS base station, said message comprising a time tag associated with a satellite position and an encoded ambiguity value derived from said satellite position;

an orbit processor configured for utilizing a broadcast orbit from said GNSS satellite to determine a second satellite position of said GNSS satellite, said satellite position and said second satellite position both being for a time represented by said time tag; and

an orbit determiner configured for resolving a third satellite position from said encoded ambiguity value and said second satellite position, said third satellite position comprising an approximation of said satellite position.

23. The GNSS receiver of claim 22, wherein said orbit determiner further comprises:

a position resolver configured for resolving said third satellite position from said encoded ambiguity value and an ambiguous portion of said second satellite position.

24. The GNSS receiver of claim 22, wherein said orbit determiner further comprises:

a delta determiner for determining a delta between said third satellite position and said second satellite position.

25. The GNSS receiver of claim 24, wherein said orbit determiner further comprises:

an orbit nudger configured for adjusting a parameter of said broadcast orbit, such that said broadcast orbit is nudged toward congruence with an orbit utilized in said GNSS base station.