1. A method comprising: receiving characteristics of first signals generated by one or more environmental sensors at a mobile device positioned at an initial location, said characteristics of said first signals being measured via said mobile device; receiving characteristics of second signals generated by one or more environmental sensors at a reference device at a known location, said characteristics of said second signals being measured via said reference device; comparing said characteristics of said first signals with said characteristics of said second signals that were generated substantially contemporaneously to determine potential matches of said first signals with said second signals; and narrowing said potential matches of said first signals with said second signals to determine that said mobile device is at least proximate to said known location based, at least in part, on said comparison and said initial location of said mobile device.