May 14, 2008 12:33 PM PDT

Yahoo hopes users will help pinpoint photos

Posted by Stephen Shankland

BURLINGAME, Calif.--Think of it as crowdsourced cartography.

In about three weeks, Yahoo plans to launch a project called Corrections in which users of the Flickr photo-sharing site can help with a thorny computing problem: providing the name of the place where a photo was taken.

Flickr's geo expert, Dan Catt, speaks at Where 2.0.

(Credit: Stephen Shankland/CNET News.com)

Flickr has 68 million photos that have been "geotagged" with latitude and longitude coordinates, said Dan Catt, who works on geographic work at Flickr, in a speech at the Where 2.0 conference here. Coordinates are fine for computers, but human beings looking at a Web site generally prefer place names to numbers.

The trouble for Flickr is that it's difficult to actually retrieve a place name for a given set of coordinates, a task called reverse geocoding. One problem, for example, is that not everyone agrees where one neighborhood ends and another begins.

With the new feature, Flickr will offer its best assessment of where a photo was taken, then let users fix it, Catt said. The site will start with offering information at the neighborhood level, but if a user doesn't agree, it will gradually step back to larger-scale regions.

"If you're not happy with what we're saying, tell us, and we'll learn from that," Catt said in an interview after his talk.

The service will remember a user's settings, so a given location that's one person's Lower Haight San Francisco neighborhood could be another's Upper Haight. As more people weigh in with what the name for a given location actually is, Yahoo will update its boundaries, Catt said.

Initially, Flickr will offer its own alternatives for a given area, but later, people will be able to type in the location, Catt added.

Most of the time the service should work fine, but geography can elicit passionate responses. "This will ruffle a lot of people's feathers," he predicted.