Method and system for ephemeris extension for GNSS applications

• US 20070299609A1
• Filed: 06/22/2007
• Published: 12/27/2007
• Est. Priority Date: 06/23/2006
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Nemerix, SA
• Inventors: Garin, Lionel, Mole, Steve
• Application Number:
  US11/812,957
• Publication Number:
  US 20070299609A1
• Time in Patent Office: Days
• US Class Current: 701/226
• 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 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver

Abstract

Methods and devices for calculating long-validity satellite prediction data, compacting such data and providing the data GNSS receivers are presented. The data are compacted using a multistage compaction approach which takes physical models into account and produces an extremely low-memory satellite prediction data file size for transmission to remote receivers.

Claims

1. A method for providing satellite position prediction data to a GNSS receiver, comprising:

receiving data indicating at least the position of a satellite with respect to at least two points in time;

computing an curve fit of an orbital element corresponding to an orbital model for each of the two points in time to yield a set of data including an estimate of the orbital parameter for each of the two points in time;

computing the coefficients of a modeling function that fits the estimates of the orbital element for each of the two points in time; and

transmitting the coefficients to a GNSS receiver.

2. The method of claim 1, wherein the orbital model is the GPS Broadcast Ephemeris model and wherein the step of computing a curve fit of an orbital element for each of the at least two points in time comprises computing a curve fit of each orbital element of the orbital model.

3. The method of claim 2, wherein the at least two points in time comprise sufficient points to span one week, and wherein the method further comprises the step of formatting the coefficients in a file with a size of less than five kilobytes.

4. The method of claim 1, wherein the step of computing the coefficients of a modeling function that fits the estimates of the orbital element for each of the two points in time comprises computing the coefficients using a variation of elements method.

5. A method for calculating the position of a satellite, comprising:

receiving data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval;

obtaining an estimate of the current time;

using the estimate of the current time and the data comprising coefficients of modeling functions to predict the value of at least one orbital element of an orbital model;

using the orbital model to predict a position of a satellite.

6. The method of claim 5, further comprising the step of storing the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval into non-volatile memory associated with a GNSS receiver.

7. The method of claim 5, further comprising the step of providing an estimate of the accuracy of a prediction file as part of ICD-GPS200 user range accuracy data.

8. The method of claim 5, further comprising the steps of

receiving a broadcast version of the coefficients of the orbital model that is more recent than the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval, from either a satellite or an assistance network;

and

updating the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval using the broadcast version of the coefficients of the orbital model.

9. A method for providing data useful for the prediction of the position of a satellite, comprising:

receiving data indicating at least the position of a satellite with respect to at least two points in time;

computing a curve fit of an orbital element corresponding to an orbital model for each of the two points in time to yield a set of data including an estimate of the orbital parameter for each of the two points in time;

computing the likely variation of the orbital element over time using at least one physical model;

computing the coefficients of a modeling function that fits the variation of the orbital element over time for each of the two points in time; and

transmitting the coefficients to a GNSS receiver.

10. The method of claim 9, wherein the orbital model is the GPS Broadcast Ephemeris model and wherein the step of computing a curve fit of an orbital element for each of the at least two points in time comprises computing a curve fit of each orbital element of the orbital model.

11. The method of claim 10, wherein the at least two points in time comprise sufficient points to span one week, and wherein the method further comprises the step of formatting the coefficients in a file with a size of less than five kilobytes.

12. The method of claim 9, wherein the step of computing the coefficients of a modeling function that fits the estimates of the orbital element for each of the two points in time comprises computing the coefficients using a variation of elements method.

13. A method for updating a satellite position model, comprising:

receiving a signal transmitted from a source that comprises at least one parameter used in a satellite orbit prediction model;

extracting from a memory data indicating a prediction with respect to time of the at least one parameter used in a satellite orbit prediction model;

updating the data indicating a prediction with respect to time of the at least one parameter used in a satellite orbit prediction model using the at least one parameter used in a satellite orbit prediction model received from the source.

14. The method of claim 13, wherein the step of updating the data indicating a prediction with respect to time of the at least one parameter used in a satellite orbit prediction model further comprises using the at least one parameter to replace a constant term in a polynomial function which is used to model the state of the parameter with respect to time.

15. The method of claim 13, wherein the source is a GNSS satellite.

16. The method of claim 13, wherein the source is an wireless cellular network.

17. A machine readable medium having program code embedded therein, wherein when the code is executed it causes a computer to perform a method comprising the steps of:

receiving data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval;

obtaining an estimate of the current time;

using the estimate of the current time and the data comprising coefficients of modeling functions to predict the value of at least one orbital element of an orbital model;

using the orbital model to predict a position of a satellite.

18. The medium of claim 17, wherein the orbital model is the GPS Broadcast Ephemeris model and wherein the method step of computing a curve fit of an orbital element for each of the at least two points in time comprises computing a curve fit of each orbital element of the orbital model.

19. The method of claim 17, wherein the method further comprises the step of providing an estimate of the accuracy of a prediction file as part of ICD-GPS200 user range accuracy data.

20. The medium of claim 18, wherein the at least two points in time comprise sufficient points to span one week, and wherein the method further comprises the step of formatting the coefficients in a file with a size of less than five kilobytes.

21. The medium of claim 17, wherein the step of computing the coefficients of a modeling function that fits the estimates of the orbital element for each of the two points in time comprises computing the coefficients using a variation of elements method.

22. A machine readable medium having program code embedded therein, wherein when the code is executed it causes a computer to perform a method comprising the steps of:

receiving data indicating at least the position of a satellite with respect to at least two points in time;

computing a curve fit of an orbital element corresponding to an orbital model for each of the two points in time to yield a set of data including an estimate of the orbital parameter for each of the two points in time;

computing the likely variation of the orbital element over time using at least one physical model;

computing the coefficients of a modeling function that fits the variation of the orbital element over time for each of the two points in time; and

transmitting the coefficients to a GNSS receiver.

23. The medium of claim 22, wherein the method further comprises the step of storing the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval into non-volatile memory associated with a GNSS receiver.

24. The medium of claim 22, wherein the method further comprises the steps of

receiving a broadcast version of the coefficients of the orbital model that is more recent than the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval, from either a satellite or an assistance network;

and

updating the data comprising coefficients of modeling functions that predict the value of an orbital element within a time interval using the broadcast version of the coefficients of the orbital model.

25. A machine readable medium having program code embedded therein, wherein when the code is executed it causes a computer to perform a method comprising the steps of:

receiving a signal transmitted from a source that comprises at least one parameter used in a satellite orbit prediction model;

extracting from a memory data indicating a prediction with respect to time of the at least one parameter used in a satellite orbit prediction model;

updating the data indicating a prediction with respect to time of the at least one parameter used in a satellite orbit prediction model using the at least one parameter used in a satellite orbit prediction model received from the source.

26. The medium of claim 25, wherein the orbital model is the GPS Broadcast Ephemeris model and wherein the step of computing a curve fit of an orbital element for each of the at least two points in time comprises computing a curve fit of each orbital element of the orbital model.

27. The medium of claim 25, wherein the at least two points in time comprise sufficient points to span one week, and wherein the method further comprises the step of formatting the coefficients in a file with a size of less than five kilobytes.

28. The medium of claim 25, wherein the step of computing the coefficients of a modeling function that fits the estimates of the orbital element for each of the two points in time comprises computing the coefficients using a variation of elements method.

29. A method for providing satellite position prediction data to a GNSS receiver, comprising:

receiving data indicating at least the position of a satellite with respect to at least two points in time;

computing data useable by a GNSS receiver having a decompaction module and a Broadcast Ephemeris position computation module to predict the position for a predetermined time of all valid GNSS satellites within a particular satellite system;

formatting the data into a file having a file, the file having a size in kilobytes that is at least fifty times smaller than the predetermined time measured in hours; and

transmitting the data do a GNSS receiver.

30. The method of claim 29, wherein the predetermined time is one week, and the file has a size of about 3 kilobytes.

31. The method of claim 29, wherein the file has a size of less than five kilobytes.