Friday, October 31. 2008

Using Flickr Images to Define Geoboundaries

Dan Catt at geobloggers (he works at Yahoo, which owns Flickr ) has a neat post showing how now it's possible to query the Flickr API to return shapes (not shapefiles, though soon you will be able to get real shapefiles) of areas as defined by Flickr's geotagging via WOE ids. Huh? Aaron of the Flickr team explains:

For every geotagged photo we store up to six Where On Earth (WOE) IDs. These are unique numeric identifiers that correspond to the hierarchy of places where a photo was taken: the neighbourhood, the town, the county, and so on up to the continent. This process is usually referred to as reverse-geocoding.

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.

This is yet another resource that depends on the masses to understand boundaries. I guess some where there is a visualization of the WOE ID boundaries (I couldn't find one on quick search); if I understand (at least vaguely) what's going on, this is just another one, powered by reverse geocoded images.