Using Where-On-Earth geotagged photos uploaded to Flickr, one is often able to reverse-engineer maps, sometimes even at the neighborhood level.
Over time this got us wondering: If we plotted all the geotagged photos associated with a particular WOE ID, would we have enough data to generate a mostly accurate contour of that place? Not a perfect representation, perhaps, but something more fine-grained than a bounding box. It turns out we can.
via Kottke