Anyone who's flown into Los Angeles can see them: the tiny, irregular-shaped turquoise gems that dot the residential landscape. It's incredible, really, how visible L.A.'s backyard pools are from the sky. You might have even found yourself counting them as you began your descent into LAX.

As researchers at MIT's Senseable City Lab, Benedikt Groß and Joseph K. Lee had both done the same thing as they sailed over the Los Angeles Basin. They reasoned: How hard would it be to use an enhanced version of that airline seat perspective—such as satellite imagery and mapping data—to count all the pools in L.A.?