Why not just add a timestamp that rotates every, say 5 seconds, to the hashed data?
That would make it infeasible to precompute the table permanently (it would have to be precomputed for a very narrow attack window, which is still better than nothing)
Arguably mapping out cities to this degree across the globe is a ginormous effort, on an order of magnitude more so than what Google Maps etc. currently provide. Thus I don't think it's entirely unreasonable to try designing something that operates purely in terms of sensory input (and of course map data where available, those approaches don't have to be mutually exclusive).