Using WiFi to triangulate instead of GPS

Question

I know its probably possible, but is it practical and doable to try and geo-position someone using WiFi to triangulate...

Thinking if I was underground and didn't have access to GPS, could I setup WiFi spots around the place to help locate someone.

Or if I was on a plane or a train (which is constantly moving), could I setup WiFi spots around the place to help locate someone.

Where would I start in doing this? Is there software components/infrastructure? If not would it be possible to do this... i.e. at a router level add location information to the packets about which router the incoming message was coming from and then the server being able to pick up on this...

Answer 1

This is exactly how the Skyhook database (built into many phones) works. It uses cell towers and WiFi points to triangulate the position in the absence of a GPS signal.