EPHEMERIS EXTENSION METHOD FOR GNSS APPLICATIONS

• US 20070247354A1
• Filed: 04/23/2007
• Published: 10/25/2007
• Est. Priority Date: 04/24/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Nemerix, SA
• Inventors: Garin, Lionel
• Granted Patent: US 7,548,200 B2
• Time in Patent Office: Days
• US Class Current: 342/357.640
• 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

Abstract

Systems, methods and devices for improving the performance of Global Navigation Satellite System (GNSS) receivers are disclosed. In particular, the improvement of the ability to calculate a satellite position or a receiver position where a receiver has degraded ability to receive broadcast ephemeris data directly from a GNSS satellite is disclosed. Correction terms can be applied to an approximate long-term satellite position model such as the broadcast almanac.

Claims

1. A method for improving the accuracy of a receiver position, comprising applying a correction to almanac data.

2. The method of claim 1, wherein the step of applying a correction to almanac data comprises obtaining a correction term from a prediction file and applying the term to an estimated satellite position.

3. The apparatus of claim 1, wherein a corrected estimated satellite position results from the step of applying a correction to almanac data and the corrected estimated satellite position is accurate to within about thirty meters.

4. The apparatus of claim 3, wherein the correction is based on data which is received from a network;

and

wherein the data allows the corrected estimated satellite position to be made accurate to within about thirty meters within several days after a reception time of the data from the network.

5. A method for generating an extended ephemeris prediction file, comprising:

obtaining data comprising a prediction of a satellite orbit;

computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data;

wherein the prediction file is valid for at least seven days and comprises less than 60480 Bytes.

6. The method of claim 5, wherein the step of computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data further comprises using both a harmonic model and a polynomial model.

7. The method of claim 5, further comprising the step of computing correction terms for satellite clock data.

8. The method of claim 5, further comprising transmitting the prediction file over a SUPL network.

9. The method of claim 5, wherein the prediction file comprises less than one kilobyte per day of validity.

10. The method of claim 5, wherein the step of computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data further comprises applying a least squares methodology to minimize the difference between the prediction of satellite orbit and the second prediction.

11. The method of claim 10, wherein the step of applying a least squares methodology to minimize the difference between the prediction of satellite orbit and the second prediction further comprises weighting data from the prediction of satellite orbit that is further in the future less than data from the prediction of satellite orbit that is nearer in the future.

15. The computer readable medium of claim 5, wherein the method further comprises transmitting the prediction file over a SUPL network.

16. The computer readable medium of claim 5, wherein the prediction file comprises less than one kilobyte per day of validity.

17. The computer readable medium of claim 5, wherein the step of computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data further comprises applying a least squares methodology to minimize the difference between the prediction of satellite orbit and the second prediction.

18. The computer readable medium of claim 10, wherein the step of applying a least squares methodology to minimize the difference between the prediction of satellite orbit and the second prediction further comprises weighting data from the prediction of satellite orbit that is further in the further less than data from the prediction of satellite orbit that is nearer in the further.

12. A computer readable medium having computer code embedded therein that, when executed, would carry out a method for generating an extended ephemeris prediction file, comprising:

obtaining data comprising a prediction of a satellite orbit;

computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data;

wherein the prediction file is valid for at least seven days and comprises less than 60480 Bytes.

13. The computer readable medium of claim 12, wherein the method step of computing correction terms related to a difference between the prediction of a satellite orbit and a second prediction resulting from almanac data further comprises using both a harmonic model and a polynomial model.

14. The computer readable medium of claim 12, wherein the method further comprises the step of computing correction terms for satellite clock data.

19. A GNSS receiver, comprising:

a communications port for receiving an almanac correction model;

a memory for storing almanac data;

circuitry for receiving GNSS signals; and

a processor for calculating the position of the receiver based on the received GNSS signals and the position of a GNSS transmitter as calculated from almanac data and the almanac correction model.

20. The GNSS receiver of claim 19, wherein the processor for calculating the position of the receiver based on the received GNSS signals and the position of the GNSS transmitters as calculated from almanac data and the almanac correction model is configured to calculate a corrected estimated GNSS transmitter position based on a harmonic correction model and a polynomial correction model.