[MertsA]

The way Google gets your approximate location is not as simple as just sending Google a list of visible access points and figuring out where the Google Maps car was when it saw that access point, it also passes along the signal strength of every access point and because the Street View car is recording signal strength and GPS location for every measurement as it's driving by it allows for a much finer resolution than just a binary "can I see this access point".

Basically, even though there was a dozen access points visible, that increases accuracy, not decreases. Like if your phone reported that it's got the same signal strength for BP and PH it will estimate that you are in between them with other access points helping to conclude that you aren't off to the side otherwise the signal strength to xyz access point would be higher.

In other words, Just sending a list of access points and signal strengths to Google gives them a rather accurate guess as to where you are in the world, much greater than just 100+ meters.

Also, Android can also figure out when you are in a car moving at highway speeds thanks to the accelerometer and is quite accurate at telling when you're walking, jogging, biking, or driving. Enable Google Now on your phone and it will send you a summary of how many miles of what activity you've done in the last month with rather surprising accuracy for me personally.