Looking at the Google geolocation API it claims: Geolocation API returns a locat

Question

Looking at the Google geolocation API it claims:

Geolocation API returns a location and accuracy radius based on information about cell towers and WiFi nodes that the mobile client can detect.

Assuming a phone is in airplane mode or has no sim card and thus cannot connect to cell towers, and assuming that GPS is also disabled, how can a phone determine its location based off of only the wifi networks in range?

Is Google using the collected data from street view wifi MAC addresses, and combining it with the GPS from the street view van? would this correlation data be stored on the phone, or downloaded as-needed via a data connection? or does this only work with known wifi networks? is it based off of the MAC address or the wifi network name?

Is this Google-specific or are there other API's/companies that can do this (and not rely on Google as their back-end?)

Explanation / Answer

Google have a list containing the MAC addresses and all the towers on a determined location. He can collect that data not only by the street view car, but from Android phones as well.

It's easy (for Google) to know the GPS coordinates of every cellphone tower on a city (or country), so correlating it with the data your phone sends is enough to get a very good idea of where you are.

Google already have a database (more or less) like this:

coordinates:tower coverage:MAC address

So, if you locate one MAC address on the list, you have the coordinates and the cell towers close to it.

Later, even if you have the cell phone disabled, your phone can connect using wifi, pass the MAC of the access point to Google, Google searchs its huge database, finds the MAC, and gets your coordinates.

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