Many digital photos are now geotagged – stamped with the latitude and longitude coordinates for the location where they were taken. David Crandall and colleagues at Cornell University in Ithaca, New York, have analysed this data, using 35 million photographs uploaded to the Flickr website.



Crandall's team found that the data offered a simple way to organise millions of photos on a global scale. Simply plotting that raw data onto an empty canvas revealed accurate maps, like this one of the 48 lower states of the US.



(Image: David Crandall)

Each map is constructed from a small subset of images. The team limited the number of photos they analysed from each Flickr user, to be sure a cluster on the map represented many users visiting a location and not "a single user taking thousands of pictures of his or her backyard", says Crandall.



(Image: David Crandall)

The enormous dataset provides a global picture of "what the world is paying attention to", the researchers say.



They ran statistical analyses to identify the largest clusters on each map. Next, they checked the text tags added to photographs in those clusters - as well as key visual features from each image - to automatically identify the world's most interesting tourist sites.



(Image: David Crandall) Advertisement

The approach can also produce accurate city maps. The River Thames is clearly visible snaking from bottom left to top right in this image.



London contains four of the seven most photographed landmarks in the world, according to Flickr: Trafalgar Square, the Tate Modern art gallery, Big Ben and the London Eye.



(Image: David Crandall)