There are many different proprietary implementations of Wi-Fi positioning, including fingerprinting techniques, which take advantage of environments with high Wi-Fi access point (AP) density such as cities and buildings.
First, the device scans and sends information about the visible Wi-Fi APs—generally the strongest APs are rated in terms of received signal. Second, this information is reported to a server on the network. The server houses a database of APs associated with geo tags and other markers. A fingerprinting algorithm is applied to the input from the handset, which then provides an estimate of the mobile’s position.
The information doesn’t always have to be provided to the network. Instead, the network may provide a subset of its central database to the handset, which then can run the fingerprinting algorithm itself. The fingerprinting algorithm can only work if a sufficiently advanced central database of Wi-Fi APs for the location of interest is available. This database is created by:
- Wardriving: Driving (or walking) in specific areas and using high-grade receivers to collect visible Wi-Fi AP data.
- Crowd sourcing: Having a smart phone constantly report observed Wi-Fi APs along with a GPS location (if available) to location servers
In some cases the handsets are used to augment the database of Wi-Fi reference points; reporting or augmenting the position data for the device or handset that is mobile - while also 'wardriving' - reporting mobile position data and AP updates at the same time. When done with the users knowlege, this can be helpful - but when done as 'secret' tracking then this can be potentially injurious to the user.
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