Location-based services that choose location algorithms based on number of detected access points within range of user device
A location beacon database and server, method of building location beacon database, and location based service using same. Wi-Fi access points are located in a target geographical area to build a reference database of locations of Wi-Fi access points. At least one vehicle is deployed including at least one scanning device having a GPS device and a Wi-Fi radio device and including a Wi-Fi antenna system. The target area is traversed in a programmatic route to avoid arterial bias. The programmatic route includes substantially all drivable streets in the target geographical area and solves an Eulerian cycle problem of a graph represented by said drivable streets. While traversing the target area, periodically receive the GPS coordinates of the GPS device. While traversing the target area, detecting Wi-Fi signals from Wi-Fi access points in range of the Wi-Fi device and recording identity information of the detected Wi-Fi access point in conjunction with GPS location information of the vehicle when the detection of the Wi-Fi access point was made. The location information is used to reverse triangulate the position of the detected Wi-Fi access point; and the position of the detected access point is recorded in a reference database.
1. A method of locating a user-device having a Wi-Fi radio, comprising:
providing a reference database of Wi-Fi access point information about Wi-Fi access points in a target area;
in response to a user application request to determine a location of a user-device having a Wi-Fi radio, receiving messages from Wi-Fi access points within range of the Wi-Fi device, each message identifying the Wi-Fi access point sending the message;
determining attributes of the messages received by the Wi-Fi radio;
accessing the reference database to obtain information about the identified Wi-Fi access points;
based on the number of Wi-Fi access points identified via received messages, choosing a corresponding location-determination algorithm from a plurality of location-determination algorithms, said chosen algorithm being suited for the number of identified Wi-Fi access points; and
using the information about the identified Wi-Fi access points and the determined attributes of said received messages and the chosen location-determination algorithm to determine the location of the user-device.
2. The method of claim 1 , wherein a first location-determination algorithm of the plurality of location-determination algorithms uses a first set of information about the identified Wi-Fi access points and a second location-determination algorithm of the plurality of location-determination algorithms uses a second set of information about the identified Wi-Fi access points, the first set of information differing from the second set of information.
3. The method of claim 1 wherein the information about the identified Wi-Fi access points are filtered to determine if the corresponding Wi-Fi access points have moved since the time the information about the Wi-Fi access points was included in the reference database.
4. The method of claim 1 wherein the reference database is located locally relative to the user-device.
5. The method of claim 1 wherein the reference database is located remotely relative to the user-device.
6. The method of claim 1 wherein the location of the user device is provided with latitude and longitude coordinates.
7. The method of claim 1 wherein the plurality of location-determination algorithms includes a simple signal strength weighted average model.
8. The method of claim 1 wherein the plurality of location-determination algorithms includes a nearest neighbor model.
9. The method of claim 1 wherein the plurality of location-determination algorithms includes a triangulation technique.
10. The method of claim 1 wherein the plurality of location-determination algorithms includes an adaptive smoothing technique based on the device velocity.
11. The method of claim 1 wherein the choice of location-determination algorithm is further based on the user application making the location request.
12. The method of claim 1 wherein the information about at least one of the Wi-Fi access points of the reference database includes signal fingerprint information of the Wi-Fi access point, the signal fingerprint information including a plurality of expected signal strength readings of messages transmitted by the Wi-Fi access point at a corresponding plurality of expected locations where the messages are received.
13. The method of claim 12 wherein the plurality of location-determination algorithms includes a technique based on signal fingerprints for more than one Wi-Fi access point.
14. The method of claim 13 wherein the technique includes determining a location by:
calculating the signal strength of messages received by the Wi-Fi radio;
comparing the calculated signal strength with the expected signal strengths of the signal fingerprint information for the more than one Wi-Fi access point to find expected signal strengths that most closely match the calculated signal strength; and
determining the location of the user-device based on expected locations that correspond to the expected signal strengths most closely matching the calculated signal strength.
15. The method of claim 1 wherein more than one location-determination algorithm from the plurality of location-determination algorithms is used to determine the location of the user-device.