Differential global positioning system using coarse GPS data for a fast time to a precise first fix

• US 6,559,793 B1
• Filed: 11/02/2001
• Issued: 05/06/2003
• Est. Priority Date: 07/27/1999
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Eschenbach, Ralph F.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): MULL, FRED H
• Application Number:
  US10/003,862
• Time in Patent Office: 550 Days
• Field of Search: 342/357.03, 342/358, 342/357.02, 701/215
• US Class Current: 342/357.31
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]

Abstract

A differential global positioning system (DGPS) using coarse data for the locations-in-space of GPS satellites for ranging to the GPS satellites and then determining a precise differentially corrected GPS location of a GPS user receiver. The coarse GPS data can be GPS almanac data or non-current GPS ephemeris data as long as the same data is used by both a GPS reference receiver and the GPS user receiver.

Claims

1. A method in a differential global positioning system (DGPS) system, comprising steps of:

at a GPS reference receiver, computing a coarse location-in-space of a GPS signal source from one of (i) GPS almanac data for said GPS signal source and (ii) non-current GPS ephemeris data for said GPS signal source;

at said GPS reference receiver, calculating a coarse range correction from said coarse location-in-space;

at a GPS user receiver, determining a measured user pseudorange between a GPS signal source and said GPS user receiver; and

calculating a precise differentially corrected user location of said GPS user receiver using said coarse range correction and said measured user pseudorange.

2. The method of claim 1, wherein:

said coarse location-in space is more than one hundred meters from an accurate location-in-space calculated according to current ephemeris data.

3. The method of claim 1, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than two hours old for said GPS signal source.

4. The method of claim 1, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than four hours old for said GPS signal source.

5. The method of claim 1, wherein:

the step of calculating said differentially corrected user location includes steps of;

calculating a coarse linearized user pseudorange from said measured user pseudorange, an assumed user location for said GPS user receiver, and said coarse location-in-space; and

using said coarse linearized user pseudorange with said coarse range correction for calculating said differentially corrected user location.

6. The method of claim 1, wherein:

the step of calculating said differentially corrected user location includes calculating said differentially corrected user location at said GPS user receiver.

7. The method of claim 1, wherein:

the step of calculating said differentially corrected user location includes calculating said differentially corrected user location at said GPS reference receiver.

8. The method of claim 1, wherein:

the step of calculating said differentially corrected user location includes using more than one of said coarse range correction and more than one said measured user pseudorange, respective ones of said more than one coarse range correction and respective ones of said more than one measured user pseudorange corresponding to respective ones of said GPS signal source.

9. A differential global positioning system, comprising:

a GPS reference receiver including a GPS source location calculator for computing a coarse location-in-space of a GPS signal source from one of (i) GPS almanac data for said GPS signal source and (ii) non-current GPS ephemeris data for said GPS signal source;

a differential correction calculator for calculating a coarse range correction based upon said coarse location-in-space; and

a communication transmitter for transmitting a reference signal having information for said coarse range correction; and

a GPS user receiver including a pseudorange calculator for determining a measured user pseudorange between the GPS user receiver and said GPS signal source;

a communication receiver for receiving said reference signal; and

a DGPS location calculator for using said coarse range correction and said measured user pseudorange for calculating a precise differentially corrected user location of said GPS user receiver.

10. The system of claim 9, wherein:

said coarse location-in space is more than one hundred meters from an accurate location-in-space calculated according to current ephemeris data.

11. The system of claim 9, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than two hours old for said GPS signal source.

12. The system of claim 9, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than four hours old for said GPS signal source.

13. The system of claim 9, wherein:

said DGPS location calculator calculates a coarse linearized user pseudorange from said measured user pseudorange, an assumed user location for said GPS user receiver, and said coarse location-in-space; and

then uses said coarse linearized user pseudorange with said coarse range correction for calculating said precise differentially corrected user location.

14. The system of claim 9, wherein:

said DGPS location calculator calculates said differentially corrected user location using more than one of said coarse range correction and more than one said measured user pseudorange, respective ones of said more than one coarse range correction and respective ones of said more than one measured user pseudorange corresponding to respective ones of said GPS signal source.

15. A differential global positioning system, comprising:

a GPS user receiver including a pseudorange calculator for determining a measured user pseudorange between the GPS user receiver and a GPS signal source; and

a communication transmitter for transmitting a user signal having information for said measured user pseudorange; and

a GPS reference receiver including a communication receiver for receiving said user signal;

a GPS source location calculator for computing a coarse location-in-space of a GPS signal source from one of (i) GPS almanac data for said GPS signal source and (ii) non-current GPS ephemeris data for said GPS signal source;

a differential correction calculator for calculating a coarse range correction from said coarse location-in-space; and

a DGPS location calculator for using said coarse range correction and said measured user pseudorange for calculating a precise differentially corrected user location of said GPS user receiver.

16. The system of claim 15, wherein:

said coarse location-in space is more than one hundred meters from an accurate location-in-space calculated according to current ephemeris data.

17. The system of claim 15, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than two hours old for said GPS signal source.

18. The system of claim 15, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than four hours old for said GPS signal source.

19. The system of claim 15, wherein:

said DGPS location calculator calculates a coarse linearized user pseudorange from said measured user pseudorange, an assumed user location for said GPS user receiver, and said coarse location-in-space; and

then uses said coarse linearized user pseudorange with said coarse range correction for calculating said precise differentially corrected user location.

20. The system of claim 15, wherein:

said DGPS location calculator calculates said differentially corrected user location using more than one of said coarse range correction and more than one said measured user pseudorange, respective ones of said more than one coarse range correction and respective ones of said more than one measured user pseudorange corresponding to respective ones of said GPS signal source.

21. A global positioning system (GPS) user receiver, comprising:

a user range calculator for using a coarse location-in-space for a GPS signal source for determining a DGPS user pseudorange between said GPS signal source and said GPS user receiver, said coarse location-in-space of said GPS signal source computed from one of (i) GPS almanac data for said GPS signal source and (ii) non-current GPS ephemeris data for said GPS signal source;

a communication receiver for receiving a reference signal having a coarse range correction based upon said coarse location-in-space; and

a DGPS location calculator for calculating a precise differentially corrected user location of said GPS user receiver from said coarse range correction and said DGPS user pseudorange.

22. The receiver of claim 21, wherein:

said coarse location-in space is more than one hundred meters from an accurate location-in-space calculated according to current ephemeris data.

23. The receiver of claim 21, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than two hours old for said GPS signal source.

24. The receiver of claim 21, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than four hours old for said GPS signal source.

25. The receiver of claim 21, wherein:

the user range calculator measures a measured user pseudorange between the GPS user receiver and said GPS signal source and linearizes said measured user pseudorange with an assumed user location for said GPS user receiver and said coarse location-in-space for providing said DGPS user pseudorange.

26. The receiver of claim 21, wherein:

the DGPS location calculator calculates said differentially corrected user location using more than one of said coarse range correction and more than one said measured user pseudorange, respective ones of said more than one coarse range correction and respective ones of said more than one measured user pseudorange corresponding to respective ones of said GPS signal source.

27. A differential global positioning system (DGPS) reference receiver, comprising:

a GPS source calculator for computing a coarse location-in-space of a GPS signal source from one of (i) GPS almanac data for said GPS signal source and (ii) non-current GPS ephemeris data for said GPS signal source;

a differential correction calculator for calculating a coarse range correction based upon said coarse location-in-space;

a communication transceiver for transmitting a reference signal having information for said coarse range correction and receiving a user signal having a measured user pseudorange between a GPS user receiver and said GPS signal source; and

a DGPS location calculator for calculating a precise differentially corrected user location of said GPS user receiver from said coarse range correction and said measured user pseudorange.

28. The receiver of claim 27, wherein:

said coarse location-in space is more than one hundred meters from an accurate location-in-space calculated according to current ephemeris data.

29. The receiver of claim 27, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than two hours old for said GPS signal source.

30. The receiver of claim 27, wherein:

said non-current GPS ephemeris data is GPS ephemeris data that is greater than four hours old for said GPS signal source.

31. The receiver of claim 27, wherein:

the DGPS location calculator calculates a coarse linearized user pseudorange from said measured user pseudorange, an assumed user location for said GPS user receiver, and said coarse location-in-space; and

then uses said coarse linearized user pseudorange with said coarse range correction for calculating said differentially corrected user location.

32. The receiver of claim 27, wherein:

the DGPS location calculator calculates said differentially corrected user location using more than one of said coarse range correction and more than one said measured user pseudorange, respective ones of said more than one coarse range correction and respective ones of said more than one measured user pseudorange corresponding to respective ones of said GPS signal source.