how does google map determine locations for phones without gps

Question

http://www.google.com/mobile/maps/

Using this on phones without gps, the locatiosn can be obtained as well.

I am currently using the html5 geocoder/gear for obtaining locations. However this only works for iphone and android. BUt how does google map get the information from phones without this capbility?

Mosaic

Answer 1

It can deduce the location of the phone from the list of towers that are in range of the phone. Each tower has a unique footprint and Google knows the location of them. It is considerably less accurate than GPS, but is still able to give your rough location.

Watch the video from Google explaining the technology. The explanation starts at 1:16.

Inconsonant

so my next question would be is it possible to get the cellid in the browser? Also is there a free api to obtain the correct mapping from a cellid? – Mosaic