Determining quality metrics utilized in building a reference database

1. A method of building a reference database used to estimate a position of a wireless local area network (WLAN) enabled device, the method comprising:

obtaining samples for WLAN access points, the samples for each WLAN access point based on WLAN signals transmitted by the WLAN access point and received by one or more scanning devices;

estimating, by software of a WLAN positioning system executing on one or more computing devices, a position of each WLAN access point based on the samples of the WLAN access point;

estimating, by the software of a WLAN positioning system, a geographical area covered by the samples of each WLAN access point;

determining, by the software of the WLAN positioning system, a quality metric of each WLAN access point based on the estimated geographical area covered by the samples of the WLAN access point; and

building, by the software of the WLAN positioning system, a reference database based on the estimated position and quality metric of each WLAN access point, the reference database used to estimate the position of the WLAN enabled device.

2. The method of claim 1 , wherein the estimating the geographical area covered by the samples is based on a number of the samples and estimated speeds of the one or more scanning devices.

3. The method of claim 2 , wherein the estimating the geographical area covered by the samples further comprises:

weighting a sample collected by a scanning device that is moving according to an estimated speed of the scanning device, the weighting to assign a greater weight to the sample if collected at a higher speed than to the sample if collected at a lower speed.

4. The method of claim 2 , wherein the estimating the geographical area covered by the samples further comprises:

eliminating duplicative samples collected by a scanning device that is stationary.

5. The method of claim 1 , wherein the building the reference database further comprises:

withholding any WLAN access points from the reference database whose quality metric does not meet a threshold.

6. The method of claim 1 , wherein the building the reference database further comprises:

storing the estimated position and quality metric of each WLAN access point in the reference database.

7. The method of claim 6 , further comprising:

determining a plurality of WLAN access points within range of the WLAN enabled device based on signals received by the WLAN enabled device;

retrieving from the reference database the estimated position and quality metric of the WLAN access points within range of the WLAN enabled device; and

estimating, by software of the WLAN positioning system, the position of the WLAN enabled device based on the estimated position and quality metric of the WLAN access points within range of the WLAN enabled device, wherein a WLAN access point's effect on the estimated position is weighted according to the WLAN access point's quality metric.

8. The method of claim 6 , further comprising:

determining a plurality of WLAN access points within range of the WLAN enabled device based on signals received by the WLAN enabled device;

retrieving from the reference database the estimated position and quality metric of the WLAN access points within range of the WLAN enabled device;

excluding at least one of the WLAN access points within range of the WLAN enabled device having a quality metric that does not meet a threshold; and

estimating, by software of the WLAN positioning system, the position of the WLAN enabled device based on the estimated position of at least one remaining WLAN access point of the WLAN access points within range of the WLAN enabled device.

9. The method of claim 1 , wherein the samples are received signal strength (RSS) samples.

10. The method of claim 1 , wherein the scanning device and the WLAN enabled device are different devices.

11. A non-transitory computer readable medium having software stored thereon, the software when executed operable to:

obtain samples for wireless local area network (WLAN) access points, the samples for each WLAN access point based on WLAN signals transmitted by the WLAN access point;

estimate a position of each WLAN access point based on the samples of the WLAN access point;

estimate a geographical area covered by the samples of each WLAN access point;

determine a quality metric of each WLAN access point based on the estimated geographical area covered by the samples of the WLAN access point; and

build a reference database based on the estimated position and quality metric of each WLAN access point, the reference database used to estimate the position of a WLAN enabled device.

12. The non-transitory computer readable medium of claim 11 , wherein the estimate of the geographical area covered by the samples is based on a number of the samples and one or more estimated speeds of one or more scanning devices that received the WLAN signals transmitted by the WLAN access point.

13. The non-transitory computer readable medium of claim 12 , wherein the software when executed is further operable to:

weight a sample collected by a scanning device that is moving according to an estimated speed of the scanning device.

14. The non-transitory computer readable medium of claim 12 , wherein the software when executed is further operable to:

eliminate duplicative samples collected by a scanning device that is stationary.

15. The non-transitory computer readable medium of claim 12 , wherein the software when executed is further operable to:

withhold any WLAN access points from the reference database whose quality metric does not meet a threshold.

16. The non-transitory computer readable medium of claim 12 , wherein the software when executed is further operable to:

store the estimated position and quality metric of each WLAN access point in the reference database.

17. The non-transitory computer readable medium of claim 11 , wherein the samples are received signal strength (RSS) samples.

18. A system for estimating positions of a wireless local area network (WLAN) enabled device, comprising:

a reference database maintained by one or more computing devices that includes an estimated position and quality metric of each a plurality WLAN access points, the estimated position of each WLAN access point based on WLAN signals transmitted by the WLAN access point, the quality metric of each WLAN access point based, at least in part, upon an estimated geographical area covered by the samples of the WLAN access point; and

the WLAN enabled device configured to executed a client-side portion of software of a WLAN positioning system, the client-side portion when executed to:

determine a plurality of WLAN access points within range of the WLAN enabled device based on signals received by the WLAN enabled device,

retrieve from the reference database the estimated position and quality metric of the WLAN access points within range of the WLAN enabled device, and

estimate the position of the WLAN enabled device based on the estimated position and quality metric of at least one of the WLAN access points within range of the WLAN enabled device, wherein a WLAN access point's effect on the estimated position of the WLAN enabled device is weighted according to the WLAN access point's quality metric or a WLAN access point is excluded from use in estimating the estimated position of the WLAN enabled device in response to the WLAN access point's quality metric.

19. The system of claim 18 , further comprising:

one or more scanning devices configured to receive the WLAN signals transmitted by each WLAN access point.

20. The system of claim 19 , wherein the geographical area covered by the samples is based on a number of the samples and one or more estimated speeds of the one or more scanning devices.