3D Landmarks from Vacation Photos

A presentation in October at the International Conference on Computer Vision showed how photos from online sites such as Flickr can be used to create a virtual 3D model of landmarks, including Notre Dame Cathedral in Paris and the Statue of Liberty in New York City. Online photo-sharing Web sites such as Flickr and Google are popular because they offer a free, easy way to share photos. Flickr now holds more than 1 billion photos; a search for "Notre Dame Paris" finds more than 80,000 files. The study authors, experts in computer vision, believe this is the world's most diverse, and largely untapped, source of digital imagery. But the freely available photos do present a challenge: these are holiday snapshots and personal photos, not laboratory-quality research images. While some may be postcard-perfect representations of a setting, others may be dark, blurry or have people covering up most of the scene.

To make the 3D digital model, the researchers first download photos of a landmark. For instance, they might download the roughly 60,000 pictures on Flickr that are tagged with the words "Statue of Liberty." The computer finds photos that it will be able to use in the reconstruction and discards pictures that are of low quality or have obstructions. Photo Tourism, a tool developed at the UW, then calculates where each person was standing when he or she took the photo. By comparing two photos of the same object that were taken from slightly different perspectives, the software applies principles of computer vision to figure out the distance to each point. In tests, a computer took less than two hours to make a 3D reconstruction of St. Peter's Basilica in Rome, using 151 photos taken by 50 different photographers. A reconstruction of Notre Dame Cathedral used 206 images taken by 92 people. All the calculations and image sorting were performed automatically. Creating 3D reconstructions of individual buildings is a first step in a long-term effort to recreate an entire city using online photographs.

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http://www.sciencedaily.com/releases/2007/11/071101191441.htm