Originally published in the Wall Street Journal Online on July 23, 2010 By Jennifer Valentino-DeVries Every minute, there are thousands of images uploaded to photo site Flickr by people who want to share them with the world. And it turns out that if you look at these photos and where they were taken, you can get a pretty good idea of the best path to take when sightseeing. Researchers at Yahoo, which owns Flickr, developed a way to gather photos and construct travel itineraries based on the location of the photos and the time between each picture. The tool, which gives people possible itineraries if they select a city and indicate how much time they have, works for five cities — Barcelona, London, Paris, New York and San Francisco. The effort, which was reported by several technology writers after a conference this summer, combines a few big trends in technology — geolocation, social data and the “wisdom of the crowd.” Social services like Foursquare, which lets users broadcast their location to friends, are making location data a hot topic, and the massive amount of information on social sites like Twitter is something that companies seem eager to use. The researchers call the Flickr photos “social breadcrumbs” — information that people leave behind when they share things publicly online. “This [tool] is tapping into that data. It puts together all those instances into a more composite view,” said Sihem Amer-Yahia, one of the researchers. “And then a new user can come in and say, ‘OK, I’m here and I have three hours. Tell me what I can do.’” To develop the tool, the researchers looked at hundreds of thousands of photos that had accurate-looking time stamps and had either been tagged with latitude and longitude or with notes on their location — like “Eiffel Tower.” Photos with such tags are a small percentage of Flickr photos, “but we have so many photos that even a small part of that makes a difference,” said Cong Yu, another Yahoo researcher. The Yahoo team figured out which photos were from tourists based on the amount of time the user stayed in a city, and then they mapped out “timed paths” based on the pictures. The researchers emphasized that they considered users’ privacy in their project. They used only photos that were made fully public, and they used only the most popular locations and itineraries, so no user’s identity could be deduced from a travel plan. Some of the photos on Flickr include people in them, but the tool itself currently provides itineraries, not those photos, even though they are public. Yahoo doesn’t have plans for a product based on the tool, but researcher Munmun De Choudhury said that it’s something that could be constructed by a software developer using Flickr’s free interface. And the next step, she said, would be refining the algorithms or gathering more data so that users get recommendations based on their preferences — like a love of art museums — or get itineraries for places farther off the beaten path.