Blue pictures were taken by locals. Red pictures were taken by tourists. Yellow pictures might be by either.
If you live in a tourist town like I do you know that there is a whole lot happening that tourists never see. This data set shows various cities around the world from both a local and a tourist point of view, using information from pictures uploaded to Flickr. Pictures that people have taken in a city for more than a month were considered to be locals, and those who took pictures of a certain place only within the last month are deemed tourists. The differences are clear in quite a few maps in the Flickr set.
Some people interpreted the Geotaggers’ World Atlas maps to be maps of tourism. This set is an attempt to figure out if that is really true. Some cities (for example Las Vegas and Venice) do seem to be photographed almost entirely by tourists. Others seem to have many pictures taken in places that tourists don’t visit.