Method and apparatus for combining measurements and determining clock offsets between different satellite positioning systems

1. A method of processing satellite signals from a first satellite navigation system and a second satellite navigation system, comprising:

measuring at least one first pseudorange between a satellite signal receiver and at least one satellite of said first satellite navigation system, said first satellite navigation system conforming to a first protocol having a first time reference frame;

measuring at least one second pseudorange between said satellite signal receiver and at least one satellite of said second satellite navigation system, said second satellite navigation system conforming to a second protocol having a second time reference frame;

obtaining a difference between the first time reference frame and the second time reference frame; and

combining said at least one first pseudorange and said at least one second pseudorange using said difference.

2. The method of claim 1 , further comprising:

computing at least one of position of said satellite signal receiver and time-of-day using said combined at least one first pseudorange and said at least one second pseudorange.

3. The method of claim 1 , wherein said steps of obtaining and combining comprise:

receiving an estimated position of said satellite signal receiver;

receiving an estimated time-of-day; and

relating said at least one first pseudorange, said at least one second pseudorange, said estimated position, and said estimated time-of-day to a plurality of position and time variables, said plurality of position and time variables including at least one time variable associated with said difference between said first time reference frame and said second time reference frame.

4. The method of claim 3 , wherein said at least one time variable comprises a delta-common bias variable.

5. The method of claim 3 , wherein said at least one time variable comprises a first common bias variable associated with said first satellite navigation system and a second common bias variable associated with said second satellite navigation system.

6. The method of claim 1 , wherein said step of obtaining comprises:

receiving an indication of said difference from a reference station.

7. The method of claim 6 , further comprising:

generating said indication at said reference station in response to signal measurements from each of said first satellite navigation system and said second satellite navigation system.

8. The method of claim 6 , further comprising:

decoding said indication from a satellite signal broadcast by at least one of said first satellite navigation system and said second satellite navigation system at said reference station.

9. The method of claim 1 , wherein said step of obtaining comprises:

receiving assistance data at said satellite signal receiver from a server; and

extracting an indication of said difference from said assistance data.

10. The method of claim 1 , wherein said first satellite navigation system comprises at least one of a GALILEO satellite system and a GLONASS satellite system, and wherein said second satellite navigation system comprises a Global Positioning System.

11. A position location system, comprising:

satellite signal receiver circuitry for measuring at least one first pseudorange to at least one satellite of a first satellite navigation system and at least one second pseudorange to at least one satellite of a second satellite navigation system, said first and second satellite navigation systems conforming to respective first and second protocols, said first and second protocol having respective first and second time reference frames; and

a processor for obtaining a difference between the first time reference frame and the second time reference frame and for combining said at least one first pseudorange and said at least one second pseudorange using said difference.

12. The system of claim 11 , wherein said processor is further configured to compute at least one of position of said satellite signal receiver and time-of-day using said combined at least one first pseudorange and said at least one second pseudorange.

13. The system of claim 11 , wherein said processor is configured to:

receive an estimated position;

receive an estimated time-of-day; and

relate said at least one first pseudorange, said at least one second pseudorange, said estimated position, and said estimated time-of-day to a plurality of position and time variables, said plurality of position and time variables including at least one time variable associated with said difference between said first time reference frame and said second time reference frame.

14. The system of claim 12 , wherein said at least one time variable comprises a delta-common bias variable.

15. The system of claim 12 , wherein said at least one time variable comprises a first common bias variable associated with said first protocol and a second common bias variable associated with said second protocol.

16. The system of claim 11 , further comprising:

a wireless transceiver;

wherein said processor is configured to receive an indication of said difference from a server using said wireless transceiver.

17. The system of claim 11 , wherein said first satellite navigation system comprises at least one of a GALILEO satellite system and a GLONASS satellite system, and wherein said second satellite navigation system comprises a Global Positioning System.

18. Apparatus for processing satellite signals from a first satellite navigation system and a second satellite navigation system, comprising:

means for measuring at least one first pseudorange between a satellite signal receiver and at least one satellite of said first satellite navigation system said first satellite navigation system conforming to a first protocol having a first time reference frame;

means for measuring at least one second pseudorange between said satellite signal receiver and at least one satellite of said second satellite navigation system, said second satellite navigation system conforming to a second protocol having a second time reference frame;

means for obtaining a difference between the first time reference frame and the second time reference frame; and

means for combining said at least one first pseudorange and said at least one second pseudorange using said difference.

19. The apparatus of claim 18 , further comprising:

means for computing at least one of position of said satellite signal receiver and time-of-day using said combined at least one first pseudorange and said at least one second pseudorange.

20. The apparatus of claim 18 , wherein said means for obtaining and combining comprise:

means for receiving an estimated position of said satellite signal receiver;

means for receiving an estimated time-of-day; and

means for relating said at least one first pseudorange, said at least one second pseudorange, said estimated position, and said estimated time-of-day to a plurality of position and time variables, said plurality of position and time variables including at least one time variable associated with said difference between said first time reference frame and said second time reference frame.