Techniques for computing location of a mobile device based on observed Wi-Fi access points

1. A method comprising:

determining characteristics of signals received from Wi-Fi access points during a traversal of a number of drivable streets within a geographic area having a radius of one or more miles, the characteristics of a given signal including a unique identifier of a Wi-Fi access point that transmitted the signal, a location where the signal was observed, and an observed signal strength at the location where the signal was observed;

calculating geographic location of each of the Wi-Fi access points in the geographic area based on locations where the signal of the Wi-Fi access point was observed and the observed signal strength at the locations where the signal of the Wi-Fi access point was observed, wherein the calculating utilizes a reverse triangulation algorithm;

storing the geographic location of each of the Wi-Fi access points in records of reference database, the records storing information descriptive of Wi-Fi access points in the geographic area;

maintaining the reference database on a non-transitory computer readable medium;

receiving a request for a current location of a mobile device;

obtaining an observed signal strength of one or more Wi-Fi access points observed by the mobile device from the current location; and

computing the current location of the mobile device using at least the observed signal strength of the one or more Wi-Fi access points observed by the mobile device in comparison to the information descriptive of Wi-Fi access points in the geographic area in the reference database.

2. The method of claim 1 , wherein the reverse triangulation algorithm weights stronger signals more than weaker signals.

3. The method of claim 1 , wherein the number is substantially all drivable streets within the geographic area.

4. The method of claim 1 , wherein the traversal is conducted according to a programmatically-determined route.

5. The method of claim 1 , further comprising:

filtering the records of the reference database to identify erroneous records, the filtering based upon clustering of records for a given Wi-Fi access point.

6. The method of claim 5 , wherein the filtering further comprises:

calculating a weighted centroid for the given Wi-Fi access point; and

designating records for the given Wi-Fi access point whose distance from the weighted centroid exceeds a threshold as being erroneous records.

7. The method of claim 5 , further comprising:

removing erroneous records from the reference database.

8. A method comprising:

determining characteristics of signals received from Wi-Fi access points during a traversal of a number of drivable streets within a geographic area having a radius of one or more miles, the characteristics of a given signal including a unique identifier of a Wi-Fi access point that transmitted the signal, a location where the signal was observed, and an observed signal strength at the location where the signal was observed;

producing a power profile of each of the Wi-Fi access points in the geographic area based on locations where the signal of the Wi-Fi access point was observed and the observed signal strength at the locations where the signal of the Wi-Fi access point was observed, the power provide indicating signal power at a plurality of positions about the Wi-Fi access point; and

storing the power profile of each of the Wi-Fi access points in records of a reference database, the records storing information descriptive of Wi-Fi access points in the geographic area;

maintaining the reference database on a non-transitory computer readable medium;

receiving a request for a current location of a mobile device;

obtaining an observed signal strength of one or more Wi-Fi access points observed by the mobile device from the current location; and

computing the current location of the mobile device using at least the observed signal strength of the one or more Wi-Fi access points observed by the mobile device in comparison to the information descriptive of Wi-Fi access points in the geographic area in the reference database.

9. The method of claim 8 , wherein the number is substantially all drivable streets within the geographic area.

10. The method of claim 8 , wherein the traversal is conducted according to a programmatically-determined route.

11. The method of claim 8 , further comprising:

filtering the records of the reference database to identify erroneous records, the filtering based upon clustering of records for a given Wi-Fi access point.

12. The method of claim 11 , wherein the filtering further comprises:

calculating a weighted centroid for the given Wi-Fi access point; and

designating records for the given Wi-Fi access point whose distance from the weighted centroid exceeds a threshold as being erroneous records.

13. The method of claim 11 , further comprising:

removing erroneous records from the reference database.

14. A system comprising:

a central network server configured to build records storing information descriptive of Wi-Fi access points in a geographic area having a radius of one or more miles, based on characteristics of signals received from Wi-Fi access points during a traversal of a number of drivable streets within the geographic area, the characteristics of a given signal including a unique identifier of a Wi-Fi access point that transmitted the signal, a location where the signal was observed, and an observed signal strength at the location where the signal was observed, the records built at least in part by calculation of a geographic location of each of the Wi-Fi access points by application of a reverse triangulation algorithm to locations where the signal of the Wi-Fi access point was observed and the observed signal strength at the locations where the signal of the Wi-Fi access point was observed; and

a reference database configured to maintain the records storing information descriptive of Wi-Fi access points in the geographic area,

wherein the central network server is further configured to compute a current location of a mobile device in response to receiving a request for a current location of the mobile device including an observed signal strength of one or more Wi-Fi access points observed by the mobile device from the current location, the computation of the current location of the mobile device based on at least a comparison of the observed signal strength of the one or more Wi-Fi access points observed by the mobile device to the information in the reference database.

15. The system of claim 14 , wherein the number is substantially all drivable streets within the geographic area.

16. The system of claim 14 , wherein the traversal is conducted according to a programmatically-determined route.

17. A system comprising:

a central network server configured to build records storing information descriptive of Wi-Fi access points in a geographic area having a radius of one or more miles, based on characteristics of signals received from Wi-Fi access points during a traversal of a number of drivable streets within the geographic area, the characteristics of a given signal including a unique identifier of a Wi-Fi access point that transmitted the signal, a location where the signal was observed, and an observed signal strength at the location where the signal was observed, the records built by producing a power profile of each of the Wi-Fi access points based on locations where the signal of the Wi-Fi access point was observed and the observed signal strength at the locations where the signal of the Wi-Fi access point was observed, the power profile indicating signal power at a plurality of positions about the Wi-Fi access point; and

a reference database configured to maintain the records storing information descriptive of Wi-Fi access points in the geographic area,

wherein the central network server is further configured to compute a current location of a mobile device in response to receiving a request for a current location of the mobile device including an observed signal strength of one or more Wi-Fi access points observed by the mobile device from the current location, the computation of the current location of the mobile device based on at least a comparison of the observed signal strength of the one or more Wi-Fi access points observed by the mobile device to the information in the reference database.

18. The system of claim 17 , wherein the number is substantially all drivable streets within the geographic area.

19. The system of claim 17 , wherein the traversal is conducted according to a programmatically-determined route.

20. A non-transitory computer-readable medium having instructions executable by one or more processors stored thereon, the instructions when executed by the one or more processors operable to:

determine characteristics of signals received from Wi-Fi access points within a geographic area having a radius of one or more miles, the characteristics of a given signal including a unique identifier of a Wi-Fi access point that transmitted the signal, a location where the signal was observed, and an observed signal strength at the location where the signal was observed;

calculate a geographic location of each of the Wi-Fi access points based on locations where signals of the Wi-Fi access point were observed and the observed signal strength at the locations where signals of the Wi-Fi access point were observed, wherein the calculating utilizes a reverse triangulation algorithm;

store the calculated geographic location of each of the Wi-Fi access points in a reference database;

receive a request for a current location of a mobile device;

determine one or more Wi-Fi access points observed by the mobile device from the current location; and

compute the current location of the mobile device using at least the one or more Wi-Fi access points observed by the mobile device in comparison to the calculated geographic locations in the reference database.

21. The non-transitory computer-readable medium of claim 20 wherein the signals received from Wi-Fi access points within the geographic area are received as part of a traversal of drivable streets within the geographic area according to a programmatically-determined route.

22. The non-transitory computer-readable medium of claim 20 , wherein the instructions when executed are further operable to:

filter the records of the reference database to identify erroneous records, wherein records that are outliers of a cluster are considered erroneous records.

23. The non-transitory computer-readable medium of claim 22 , wherein the instructions that when executed are operable to filter include instructions that when executed are operable to:

calculate a weighted centroid for a given Wi-Fi access point; and

designate records associated with the given Wi-Fi access point whose distance from the weighted centroid exceeds a threshold as being erroneous records.

24. The non-transitory computer-readable medium of claim 22 , wherein the instructions that when executed are operable to filter include instructions that when executed are operable to:

remove erroneous records from the reference database.