Locating satellites

• US 7,830,304 B2
• Filed: 07/06/2007
• Issued: 11/09/2010
• Est. Priority Date: 07/07/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Mattos, Philip
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US11/825,674
• Publication Number:
  US 20090009389A1
• Time in Patent Office: 1,222 Days
• Field of Search: 342/357.09, 342/357.15, 342/357.23, 342/357.45
• US Class Current: 342/357.23
• 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

A system and method of locating the position of a satellite or a user using a satellite positioning system. The system and method includes receiving, at a terminal, satellite positioning data for at least one specified time period over a communications channel. In addition, the system includes storing, at the terminal, the satellite positioning data for the at least one specified time period. Responsive to an event at a later time, the system generally calculates, at the terminal, the satellite position at the later time based only on the satellite positioning data for the at least one specified time period.

Claims

1. A method of locating the position of a satellite in a satellite positioning system, the method comprising:

receiving, at a terminal, satellite positioning data for at least one specified time period over a communications channel;

storing, at the terminal, the satellite positioning data for the at least one specified time period;

responsive to an event at a later time, calculating, at the terminal, the satellite position at the later time based on the satellite positioning data for the at least one specified time period, wherein the satellite positioning data for the at least one specified time period comprises ephemeris data for a first time period received at a first time, ephemeris data for a second time period received at a second time, and ephemeris data for a third time period received at a third time;

estimating positions of the satellite at the first and second times using the ephemeris data for the third time period;

calculating errors in the estimated positions at the first time using the ephemeris data for the first time period and at the second time using the ephemeris data for the second time period wherein the calculation of errors comprises fitting a curve to the errors and using the curve to give an extrapolated error value at the later time and calculating the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.

2. The method according to claim 1, wherein said later time is outside said at least one specified time period.

3. The method according to claim 1, wherein the third time is earlier than the first and second time.

4. The method according to claim 1, wherein the third time is more recent than the first and second time.

5. The method according to claim 1 further comprising:

fitting a curve to the errors and storing parameters defining the curve at the user terminal; and

removing the ephemeris data for the first and second time period stored at the terminal.

6. The method according to claim 5, wherein the step of calculating further comprises:

creating a curve from the parameters using the curve to give an extrapolated error value at the later time; and

calculating the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.

7. The method according to claim 5, wherein the third time is more recent than the first and second time.

8. The method according to claim 1, wherein the event is a user actuated event.

9. A terminal to locate the position of a satellite in a satellite positioning system, the terminal comprising:

a receiver to receive satellite positioning data for at least one specified time period over a communications channel;

a memory to store the satellite positioning data for the at least one specified time period wherein the satellite positioning data for the at least one specified time period comprises ephemeris data for a first time period received at a first time, ephemeris data for a second time period received at a second time, and ephemeris data for a third time period received at a third time; and

a circuit to calculate, responsive to an event at a later time, the satellite position at the further time based only on the satellite positioning data for the at least one specified time period, wherein the circuit further estimates the positions of the satellite at the first and second times using the ephemeris data for the third time period, calculates errors in the estimated positions at the first time using the ephemeris data for the first time period and at the second time using the ephemeris data for the second time period, fits at least one a curve to the errors, uses the at least one curve to give an extrapolated error value at the later time, and calculates the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.

10. The terminal of claim 9, wherein the terminal is at least one of:

a Galileo receiver and a global positioning system (GPS) receiver.

11. The terminal according to claim 9, wherein said later time is outside said at least one specified time period.

12. A method of determining the local position of a user of a terminal at the request of the user, comprising:

calculating, at the terminal, the position of a satellite in a satellite positioning system at a time of the request based only on satellite positioning data previously received at the terminal for at least one specified time period over a communications channel and stored at the terminal wherein the satellite positioning data for the at least one specified time period comprises ephemeris data for a first time period received at a first time, ephemeris data for a second time period received at a second time, and ephemeris data for a third time period received at a third time;

estimating positions of the satellite at the first and second times using the ephemeris data for the third time period;

calculating errors in the estimated positions at the first time using the ephemeris data for the first time period and at the second time using the ephemeris data for the second time period;

fitting a curve to the errors;

using the curve to give an extrapolated error value at the later time; and

calculating the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.

13. The method according to claim 12, wherein said later time is outside said at least one specified time period.

14. The method according to claim 12, wherein the third time is earlier than the first and second time.

15. The method according to claim 12, wherein the third time is more recent than the first and second time.

16. The method according to claim 12 further comprising:

fitting a curve to the errors and storing parameters defining the curve at the user terminal; and

removing the ephemeris data for the first and second time period stored at the terminal.

17. The method according to claim 12 wherein the terminal comprises a global positioning system (GPS) receiver configured to locate the position of a satellite in a global positioning system.

18. The method according to claim 12 wherein the terminal comprises a GLONASS receiver configured to locate the position of a satellite in a GLONASS positioning system.

19. The method according to claim 12, wherein the step of calculating further comprises:

creating a curve from the parameters using the curve to give an extrapolated error value at the later time; and

calculating the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.

20. The method according to claim 12, wherein the third time is more recent than the first and second time.