PREDICTION REFRESH METHOD FOR EPHEMERIS EXTENSIONS

• US 20080186228A1
• Filed: 02/04/2008
• Published: 08/07/2008
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Nemerix, SA
• Inventors: Garin, Lionel, Gupta, Pramod, Venkatraman, SaiPradeep
• Granted Patent: US 8,497,801 B2
• Time in Patent Office: Days
• US Class Current: 342/357.12
• 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 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver
• CPC Class Codes: G01S 19/42 Determining position

Abstract

Systems, methods and devices for using ephemeris data in GNSS receivers and systems are provided. Receivers using synthetic ephemeris data for longer ephemeris availability under poor reception conditions are updated using a variety of techniques that allow for the transfer of accurate information onto degraded synthetic ephemeris information.

Claims

1. A method for using satellite ephemeris data in a GNSS receiver, comprising:

obtaining a synthetic ephemeris data set;

using the synthetic ephemeris data set in combination with other data to compute a position of the GNSS receiver;

updating the synthetic ephemeris data set, at a time after obtaining the synthetic ephemeris data set, using information obtained from broadcast ephemeris data.

2. The method of claim 1, wherein the step of updating the synthetic ephemeris data set comprises providing for an improvement of a clock correction parameter.

3. The method of claim 2, wherein the step of providing for an improvement of a clock correction parameter comprises measuring a pseudorange to a satellite and calculating an expected range to the satellite.

4. The method of claim 2, wherein the step of providing for an improvement of a clock correction parameter comprises attributing a difference between a measured pseudorange and an expected range to the clock correction parameter.

5. A method for refreshing satellite ephemeris data, comprising:

measuring a range to a first satellite to obtain a first pseudorange;

attributing an error in the first pseudorange to a clock correction parameter of a satellite ephemeris data set; and

providing for a correction of the clock correction parameter.

6. The method of claim 5, further comprising the step of:

obtaining a current position.

7. The method of claim 5, further comprising the steps of:

obtaining broadcast ephemeris data; and

using a parameter from the broadcast ephemeris data in the satellite ephemeris data set.

8. The method of claim 6, wherein the step of providing for a correction of the clock correction parameter comprises comparing the first pseudorange with an expected range based on the current position to calculate the error.

9. The method of claim 6, wherein the step of providing for a correction of the clock correction parameter comprises

calculating a range to a second satellite;

measuring a pseudorange to the second satellite;

using a difference-based relationship to obtain an estimate of a clock error.

10. The method of claim 9, further comprising using a position estimate obtained from a non-GNSS source to improve the estimate of the clock error.

11. The method of claim 10, wherein the non-GNSS source is a map-matching program.

12. The method of claim 10, wherein the non-GNSS source is a communications network.

13. The method of claim 5, wherein the step of providing for a correction of the clock correction parameter comprises storing a correction factor that is to be combined with the clock correction parameter before the clock correction parameter is used to calculate a position.

14. A GNSS receiver, comprising:

a receiver section for receiving GNSS signals;

a processor for processing data derived from GNSS signals;

wherein the processor is configured to update a synthetic ephemeris data set using information obtained from broadcast ephemeris data.

15. The method of claim 14, wherein the processor is further configured to provide for an improvement of a clock correction parameter.

16. The method of claim 15, wherein the processor is further configured to measure a pseudorange to a first satellite and calculate an expected range to the first satellite.

17. The method of claim 15, wherein the processor is further configured to attribute a difference between a measured pseudorange and an expected range to the clock correction parameter.

18. The method of claim 14, wherein the receiver is further configured to obtain broadcast ephemeris data and the processor is further configured to use parameters from the broadcast ephemeris data in the synthetic ephemeris data set.

19. The method of claim 16, wherein the processor is further configured to compare the pseudorange with the expected range to calculate an error.

20. The method of claim 16, wherein the processor is further configured to calculate a range to a second satellite;

measure a pseudorange to the second satellite; and

use a difference-based relationship to obtain an estimate of a clock error.