Satellite based positioning method and system for coarse location positioning

1. A satellite based positioning method, comprising:

a mobile station using stored satellite sub-almanacs to acquire a plurality of satellites;

the mobile station using the satellite sub-almanacs to take measurements;

the mobile station using the sub-almanacs to calculate a coarse position of the mobile station;

the mobile station transmitting to coarse position to a network;

the mobile station transmitting an indication of an acceptable level of error to the network;

determining whether any of the sub-almanacs require replacement, including determining whether the acceptable level of error has been exceeded; and

transmitting any required replacement sub-almanacs to the mobile station.

2. The method of claim 1 , wherein the mobile station further stores the coarse position, and wherein the mobile station transmits the come position to the network after a period of time.

3. The method of claim 1 , further comprising:

the network calculating a correction to the coarse position; and

the network transmitting the correction to the mobile station.

4. The method of claim 3 , further comprising the mobile station transmitting an identification list to the network, wherein the identification list comprises identifications of particular satellites used in calculating the cause position, and identifications of particular sub-almanacs for each of the particular satellites.

5. The method of claim 4 , wherein calculating the correction comprises calculating a position correction vector over satellites used to calculate the coarse position.

6. The method of claim 4 , wherein calculating the correction comprises calculating a pseudorange correction for each satellite used to calculate the coarse position.

7. The method of claim 4 , wherein calculating the correction comprises calculating a differential correction, wherein the differential correction accounts for discrepancies between calculation results obtained using ephemeris data and pseudorange data observed by a reference receiver at a known location.

8. The method of claim 1 , further comprising:

the mobile station receiving a reference position; and

the mobile station using the reference position to calculate the coarse position.

9. The method of claim 8 , wherein the mobile station transmitting the coarse position comprises transmitting a position difference between the reference position and the coarse position.

10. A satellite based positioning system, comprising:

a location server in a network, wherein the location server receives satellite positioning data, including global positioning system (GPS) data;

a base station in the network;

a mobile station configured to communicate with the base station, wherein the mobile station comprises,

a memory that stores satellite sub-almanac data;

a central processing unit (CPU) configured to calculate a coarse position using the sub-almanac data; and

a transceiver configured to transmit the coarse position to the network and

an indication of an acceptable level of error to the network; and

wherein the location server is configured to determine whether any of the sub-almanacs require replacement including determining whether the acceptable level of error has been exceeded, and to transmit any required replacement sub-almanacs to the mobile station.

11. The system of claim 10 , wherein the location server is configured to calculate a correction to the coarse position.

12. The system of claim 11 , wherein the mobile station is further configured to transmit an identification list to the network, wherein the identification, list comprises identifications of particular satellites used in calculating the coarse position, and identification of particular sub-almanacs for each of the particular satellites.

13. The system of claim 10 , wherein the mobile station is further configured to receive a reference position, and to use the reference position to calculate the coarse position.

14. The system of claim 13 , wherein transmitting the coarse position comprises transmitting a position difference between the reference position and the coarse position.

15. The system of claim 10 , further comprising the mobile station transmitting an identification list to the network, wherein the identification list comprises identifications of particular satellites used in calculating the coarse position, and identification of particular sub-almanacs for each of the particular satellites.

16. The system of claim 15 , wherein calculating the correction comprises calculating a position correction vector over satellites used to calculate the coarse position.

17. The system of claim 15 , wherein calculating the correction comprises calculating a pseudorange correction for each satellite used to calculate the coarse position.

18. The system of claim 15 , wherein calculating the correction comprises calculating a differential correction, wherein the differential correction accounts for discrepancies between calculation results obtained using ephemeris data and pseudorange data observed by a reference receiver at a known location.

19. A method of determining a position of a mobile-station, the method comprising:

the mobile station storing sub-almanac data;

the mobile station using the sub-almanac data to calculate a coarse position;

the mobile station transmitting the coarse position and an identification list to a network, wherein the identification list comprises identifications of particular satellites used in calculating the coarse position, and identifications of particular sub-almanacs for each of the particular satellites;

the network calculating an estimated range error per satellite; and

if the estimated range error exceeds a predetermined threshold for particular sub-almanacs, transmitting replacement sub-almanacs to the mobile station.

20. The method of claim 19 , further comprising, if the estimated range error does not exceed the predetermined threshold for any of the sub-almanacs, calculating a final position solution for the mobile station.

21. The method of claim 19 , further comprising:

re-transmitting a position request to the mobile station; and

the mobile station recalculating a coarse position using the replacement sub-almanacs.

22. A satellite based positioning method for a mobile station in communication with a network, the method comprising:

the mobile station transmitting an identification list comprising identifications of particular satellites thought to be in view, and identifications of particular sub-almanacs for each of the particular satellites;

the network estimating range errors for each of the particular sub-almanacs;

the network transmitting replacement sub-almanacs to the mobile station for each sub-almanac for which a predetermined range error threshold is exceeded; and

the mobile station calculating a coarse position using the sub-almanacs including any replacement sub-almanacs.

23. The method of claim 22 , further comprising:

the mobile station transmitting the coarse position and a new identification list to the network; and

the network calculating a final position solution for the mobile station.

24. A satellite based positioning method for a mobile station in communication with a network, the method comprising:

the mobile station calculating which particular satellites the mobile station tracks;

the mobile station determining whether any sub-almanacs associated with the particular satellites are older than a predetermined maximum age;

if one or more of the sub-almanacs are older than the predetermined age, the mobile station transmitting to the network an identification list and an error threshold, wherein the identification list comprises identifications of particular satellites thought to be in view, and identifications of particular sub-almanacs for each of the particular satellites;

the network estimating range errors fur each of the particular satellites; and

the network transmitting replacement sub-almanacs for any satellites for which the range error exceeds the error threshold.

25. The method of claim 24 , further comprising the mobile station using stored data and any replacement sub-almanacs to acquire satellites and take measurements.

26. The method of claim 25 , further comprising:

the mobile station calculating a coarse position;

the mobile station transmitting the coarse position and an identification list to the network; and

the network calculating a final position solution for the mobile station.

27. A machine-readable medium having instructions stored thereon, which when executed cause a processor to perform a satellite positioning process, wherein the process comprises:

using stored satellite sub-almanacs to acquire a plurality of satellites;

using the satellite sub-almanacs to take measurements;

using the sub-almanacs to calculate a coarse position of a mobile station;

transmitting the coarse position to a network;

transmitting an indication of an acceptable level of error to the network;

determining whether any of the sub-almanacs require replacements including determining whether the acceptable level of error has been exceeded; and

transmitting any required replacement sub-almanacs to the mobile station.

28. The machine-readable medium of claim 27 , wherein the process further comprises storing the coarse position, and transmitting the coarse position to the network after a period of time.

29. The machine-readable medium of claim 27 , wherein the process further comprises:

calculating a correction to the coarse position; and

transmitting the correction to the mobile station.

30. The machine-readable medium of claim 29 , wherein the process further comprises transmitting an identification list to the network, wherein the identification list comprises identifications of particular satellites used in calculating the coarse position, and identification of particular sub-almanacs for each of the particular satellites.

31. The machine-readable medium of claim 30 , wherein calculating the correction comprises calculating a position correction vector over satellites used to calculate the coarse position.

32. The machine-readable medium of claim 30 , wherein calculating the correction comprises calculating a pseudorange correction for each satellite used to calculate the coarse position.

33. The machine-readable medium of claim 30 , wherein calculating the correction comprises calculating a differential correction, wherein the differential correction accounts for discrepancies between calculation results obtained using ephemeris data and pseudorange data observed by a reference receiver at a known location.

34. The machine-readable medium of claim 27 , wherein the process further comprises:

receiving a reference position; and

using the reference position to calculate the coarse position.

35. The machine-readable medium of claim 34 , wherein transmitting the coarse position comprises transmitting a position difference between the reference position and the coarse position.