How the Hell do They do That?

I was playing around with Google Maps on my savagely hacked Nook Color "e-book reader" (well it was - now it's an Android tablet), when I noticed this:



That is in reality a circle of I guess less than 100 m in diameter and the center is less than 20 m from my actual location at the time (which is the tall building to the left of the circle of confidence - right next to the pool that is half visible).  Now I am fairly used to this from various mobile phones with built-in GPS, but here is the interesting part: "This is a Nook Color"!!!  It has not got built-in GPS and it most certainly hasn't got any kind of cell-phone radio built-in either.  The only means of wireless connectivity is Wifi.  How the hell do they do that???

Technically I reckon there are two possibilities:

1. They use whatever IP address I connect from when I access the maps server
2. They triangulate the Wifi SID's

I am fairly convinced it's not the first of these options.  By checking the IP address I reckon they might be able to put my location within perhaps a few kilometers if their database of IP addresses are extremely detailed, but there is no way they could possibly achieve the level of confidence that they display here.

In other words they must use Wifi triangulations and the fact that they can do that in the first place is quite mind boggling really.  People put up new wireless access points and switch off old ones all the time.  In other words, Google must have access to information about visible access points in "near real time".  There is only one way they can do that and that is harvesting statistics each time a GPS and Wifi enabled phone connect to Google.

I am not particularly worried about Google knowing where I am.  After all - that is the whole point of their Latitude service.  However I do find it slightly dodgy if Google collect the statistical information from GPS enabled devices.  When I use my Nokia 5800 to connect to Google Maps, obviously it will send the GPS information about my location to Google.  But the fact that they might send information about visible Wireless access points (and probably cell phone towers too) is a bit questionable.  While I don't pay any traffic charges for my 3G connection a lot of people do and I don't remember Google telling me that I am contributing to their business in this way.

I guess I will have to do some network sniffing in the near future.