System and method for using a satellite positioning system to filter WLAN access points in a hybrid positioning system

1. A method of determining the location of a WLAN and satellite enabled device by using satellite measurements and satellite information to weigh WLAN access points (APs), the method comprising:

detecting WLAN APs in range of the WLAN and satellite enabled device;

retrieving location estimates of the WLAN APs;

obtaining satellite measurements and satellite information from at least two satellites to provide a plurality of possible satellite-based locations of the device; and

providing a weight for each WLAN AP based on the distance from the WLAN APs to the nearest location among the plurality of possible satellite-based locations of the device.

2. The method of claim 1 comprising using the weight for each WLAN AP in a location algorithm to determine the location of the device.

3. The method of claim 1 , wherein the plurality of possible satellite-based locations of the device comprise a region of possible location solutions for the device.

4. The method of claim 1 , wherein a relatively higher weight corresponds to a WLAN AP whose location estimate is closer to the plurality of possible satellite-based locations of the device relative to the other location estimates of the WLAN APs.

5. The method of claim 4 , wherein a location estimate of a WLAN AP is closer to the plurality of possible satellite-based locations of the device if the location estimate of the WLAN AP comprises a distance within about one order of magnitude of the coverage area of the WLAN AP.

6. The method of claim 1 , wherein a relatively lower weight corresponds to a WLAN AP whose location estimate is farther from the satellite-based estimation of the location of the device relative to the other location estimates of the WLAN APs.

7. The method of claim 6 , wherein a WLAN AP is farther from the satellite-based estimation of the location of the device if the location estimate of the WLAN AP comprises a distance about an order of magnitude above the coverage area of the WLAN AP.

8. The method of claim 6 , wherein if the location estimate of the WLAN AP is determined to be farther from the plurality of possible satellite-based locations of the device, the position of the WLAN and satellite enabled device is calculated without data from the far WLAN AP.

9. The method of claim 1 , wherein the weight is based on the consistency between the location estimates of the WLAN APs and the plurality of possible satellite-based locations of the device.

10. The method of claim 1 comprising:

eliminating, from use in determining the location of the WLAN and satellite enabled device, WLAN APs whose location estimates are not consistent with the plurality of possible satellite-based locations of the device.

11. The method of claim 10 , wherein the WLAN AP location consistency with the satellite measurements and satellite information is measured by applying each of the WLAN AP location estimates to the satellite measurements and satellite information, and calculating the internal SPS receiver clock bias for each WLAN AP location estimate.

12. The method of claim 10 comprising calculating an internal SPS receiver clock bias by considering the location estimates of each WLAN AP as an initial position and the measurements and information from each satellite.

13. The method of claim 10 , wherein the consistency of the internal SPS receiver clock bias for each of the WLAN AP location estimates is used as an indication of distance between the WLAN AP location estimate and the plurality of possible satellite-based device locations.

14. The method of claim 10 , wherein calculating the consistency of the internal SPS receiver clock bias for each WLAN AP location estimate comprises calculating the standard deviation or the mean square error of the internal SPS receiver clock bias.

15. The method of claim 1 , wherein the location estimates of the WLAN APs are based on characteristics of the WLAN APs, the characteristics including at least one of received signal strength, location of the WLAN AP, signal-to-noise ratio, time of arrival, and last-known location of the WLAN AP.

16. A system for determining the location of a WLAN and satellite enabled device by using satellite measurements and satellite information to weigh WLAN access points (APs), the system comprising:

a hybrid positioning module comprising:

a WLAN positioning module for receiving information from one or more WLAN access points, and for receiving location estimates of the one or more WLAN APs;

a satellite positioning module for providing a plurality of possible locations of the device based on satellite measurements and satellite information from at least two different satellites; and

logic contained in the hybrid positioning module for providing a weight for each AP based on the distance from the WLAN APs to the nearest location estimate among the plurality of possible satellite-based locations of the device.

17. The system of claim 16 , wherein a relatively higher weight corresponds to a WLAN AP whose location estimate is closer to the plurality of possible satellite-based locations of the device relative to the other WLAN APs.

18. The system of claim 17 , wherein a WLAN AP is closer to the plurality of possible satellite-based locations of the device if the location estimate of the WLAN AP comprises a distance within about one order of magnitude of the coverage area of the WLAN AP.

19. The system of claim 16 , wherein a relatively lower weight corresponds to a WLAN AP whose location estimate is farther from the satellite-based estimation of the location of the device relative to the other WLAN APs.

20. The system of claim 19 , wherein a WLAN AP is farther from the satellite-based estimation of the location of the device if the location estimate of the WLAN AP is at a distance about an order of magnitude above the coverage area of the AP.

21. The system of claim 20 , wherein if the location estimate of the WLAN AP is determined to be farther from the plurality of possible satellite-based locations of the device, the position of the WLAN and satellite enabled device is calculated without data from the farther WLAN AP.

22. The system of claim 16 , wherein the weight is based on the consistency between the location estimates of the WLAN APs and the plurality of possible satellite-based locations of the device.

23. The system of claim 16 , wherein WLAN APs whose location estimates are not consistent with the plurality of possible satellite-based locations of the device are eliminated from use in determining the location of the WLAN and satellite enabled device.

24. The system of claim 22 , wherein the WLAN AP location consistency with the satellite measurements and satellite information is measured by applying each of the WLAN AP location estimates to the satellite measurements and satellite information, and by calculating the internal SPS receiver clock bias for each WLAN AP location estimate.

25. The system of claim 22 comprising calculating an internal SPS receiver clock bias by considering the location estimate of each WLAN AP as an initial position and the measurements and information from each satellite.

26. The system of claim 22 , wherein the consistency of the internal SPS receiver clock bias for each of the WLAN AP location estimates is used as an indication of distance between the WLAN AP location estimate and the plurality of possible satellite-based locations.

27. The system of claim 22 , wherein calculating the consistency of the internal SPS receiver clock bias for each WLAN AP location estimate comprises calculating the standard deviation or the mean square error of the internal SPS receiver clock bias.

28. The system of claim 16 , wherein the location estimates of the WLAN APs are based on characteristics of the WLAN APs, the characteristics including at least one of received signal strength, location of the WLAN AP, signal-to-noise ratio, time of arrival, and last-known location of the WLAN AP.