System and method for using a satellite positioning system to filter WLAN access points in a hybrid positioning system
This disclosure describes a system and method for using a satellite positioning system to filter WLAN access points in a hybrid positioning system. In some embodiments, the method can include detecting WLAN APs in range of the WLAN and satellite enabled device, obtaining satellite measurements from at least two satellites to provide a plurality of possible satellite locations of the device, and providing a weight for each AP based on the distance from the WLAN APs to the possible satellite locations of the device.
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:
identifying WLAN APs in range of the WLAN and satellite enabled device;
retrieving location estimates of the WLAN APs;
grouping the WLAN APs into clusters of at least one WLAN AP based on the 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 cluster of WLAN APs based on a distance from the clusters of 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 cluster of WLAN APs 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 cluster of WLAN APs whose location estimate is closer to the plurality of possible satellite-based locations of the device relative to the location estimates of the other clusters of WLAN APs.
5. The method of claim 4 , wherein a location estimate of a cluster of WLAN APs is closer to the plurality of possible satellite-based locations of the device if the location estimate of the cluster of WLAN APs comprises a distance within about one order of magnitude of the coverage area of the cluster of WLAN APs.
6. The method of claim 1 , wherein a relatively lower weight corresponds to a cluster of WLAN APs whose location estimate is farther from the satellite-based estimation of the location of the device relative to the location estimates of the other clusters of WLAN APs.
7. The method of claim 6 , wherein a cluster of WLAN APs is farther from the satellite-based estimation of the location of the device if the location estimate of the cluster of WLAN APs comprises a distance about an order of magnitude above the coverage area of the cluster of WLAN APs.
8. The method of claim 6 , wherein if the location estimate of the cluster of WLAN APs 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 cluster of WLAN APs.
9. The method of claim 1 , wherein the weights are based on the consistency between the location estimates of the clusters of WLAN APs and the plurality of possible satellite-based locations of the device.
10. The method of claim 1 , wherein the location estimates of the clusters of WLAN APs are based on characteristics of the WLAN APs of the clusters, the characteristics including at least one of received signal strength, location of the WLAN APs, signal-to-noise ratio, time of arrival, and last-known location of the WLAN APs.
11. The method of claim 1 , wherein the plurality of possible satellite-based locations of the device is based on a subset of the satellite measurements and satellite information.
12. The method of claim 1 , wherein the satellite measurements and satellite information is obtained from less than four satellites.
13. The method of claim 1 comprising:
eliminating, from use in determining the location of the WLAN and satellite enabled device, clusters of WLAN APs whose location estimates are not consistent with the plurality of possible satellite-based locations of the device.
14. The method of claim 13 , wherein the WLAN AP cluster location consistency with the satellite measurements and satellite information is measured by applying each of the WLAN AP cluster location estimates to the satellite measurements and satellite information, and calculating the internal SPS receiver clock bias for each WLAN AP cluster location estimate.
15. The method of claim 13 , comprising calculating an internal SPS receiver clock bias by considering (i) the location estimates of each cluster of WLAN APs as an initial position and (ii) the measurements and information from each satellite.
16. The method of claim 13 , wherein the consistency of the internal SPS receiver clock bias for each of the WLAN AP cluster location estimates is used as an indication of distance between the WLAN AP cluster location estimate and the plurality of possible satellite-based device locations.
17. The method of claim 13 , wherein calculating the consistency of the internal SPS receiver clock bias for each WLAN AP cluster location estimate comprises calculating the standard deviation or the mean square error of the internal SPS receiver clock bias.
18. 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 APs, for receiving location estimates of the one or more WLAN APs, and for grouping the WLAN APs into clusters of one or more WLAN APs based on the location estimates of the one or more WLAN APs;
a satellite positioning module for providing a plurality of possible locations of the WLAN and satellite enabled 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 cluster of WLAN APs based on the distance from the clusters of WLAN APs to the nearest location estimate among the plurality of possible satellite-based locations of the device.
19. The system of claim 18 , wherein a relatively higher weight corresponds to a cluster of WLAN APs whose location estimate is closer to the plurality of possible satellite-based locations of the device relative to the other clusters of WLAN APs.
20. The system of claim 19 , wherein a cluster of WLAN APs is closer to the plurality of possible satellite-based locations of the device if the location estimate of the cluster of WLAN APs comprises a distance within about one order of magnitude of the coverage area of the cluster of WLAN APs.
21. The system of claim 18 , wherein a relatively lower weight corresponds to a cluster of WLAN APs whose location estimate is farther from the satellite-based estimation of the location of the device relative to the other clusters of WLAN APs.
22. The system of claim 21 , wherein a cluster of WLAN APs is farther from the satellite-based estimation of the location of the device if the location estimate of the cluster of WLAN APs is at a distance about an order of magnitude above the coverage area of the cluster of WLAN APs.
23. The system of claim 22 , wherein if the location estimate of the cluster of WLAN APs 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 cluster of WLAN APs.
24. The system of claim 18 , wherein the weights are based on the consistency between the location estimates of the clusters of WLAN APs and the plurality of possible satellite-based locations of the device.
25. The system of claim 18 , wherein clusters of 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.
26. The system of claim 24 , wherein the WLAN AP cluster location consistency with the satellite measurements and satellite information is measured by applying each of the WLAN AP cluster location estimates to the satellite measurements and satellite information, and by calculating the internal SPS receiver clock bias for each WLAN AP cluster location estimate.
27. The system of claim 24 comprising calculating an internal SPS receiver clock bias by considering (i) the location estimate of each cluster of WLAN APs as an initial position and (ii) the measurements and information from each satellite.
28. The system of claim 24 , wherein the consistency of the internal SPS receiver clock bias for each of the WLAN AP cluster location estimates is used as an indication of distance between the WLAN AP cluster location estimate and the plurality of possible satellite-based locations.
29. The system of claim 24 , wherein calculating the consistency of the internal SPS receiver clock bias for each WLAN AP cluster location estimate comprises calculating the standard deviation or the mean square error of the internal SPS receiver clock bias.
30. The system of claim 18 , wherein the location estimates of the clusters of WLAN APs are based on characteristics of the WLAN APs of the clusters, 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.
31. The system of claim 18 , wherein the plurality of possible satellite-based locations of the device is based on a subset of the satellite measurements and satellite information.
32. The system of claim 18 , wherein the satellite measurements and satellite information is obtained from less than four satellites.