Last week, photo-sharing website Flickr announced new features that let people easily assign a location to a photo and search for pictures on a map, an activity called “geotagging.” Its latest offering is enhanced by advanced search technology that Flickr leverages from Yahoo–its parent company–which allows newly geotagged photos to be searchable within a minute.

Adding location information to pictures has broad social implications, says Stewart Butterfield, founder and chief executive officer of Flickr. As more people geotag photos and more Flickr applications are built to take advantage of geotagging, he says, people will use the service in novel ways. For instance, geotagged pictures could complement traditional Web searching: a search for designer jeans might include the picture of a local boutique with a sale that day. For travel, he says, geotagged photos could let a person check on a destination before a flight is booked. And location-based search could redefine local news to include, say, an active construction project in a neighborhood.

A number of websites already allow users to add location information to their pictures and to search geographically, including Zooomr, a photo-sharing site; Mappr, which maps Flickr photos; and Platial, an online atlas built with user-generated pictures, video, and comments.

Flickr’s geotagging feature may distinguish itself, however, in its ease of use and efficiency. To tag a picture with a location, a user simply drags the image from a panel to a location the Yahoo map. Within about a minute, internal search-engine technology at Yahoo updates the photo and tag database, allowing the picture to be searched.

Because it’s so easy, says Jason Wilson, co-creator of Platial, “I think a lot of people will start using it to geotag their pictures.” Already, Flickr stores roughly a quarter of a billion photos, and around one million are uploaded to its servers on a busy day. Two days after its geotagging tool was released, more than two million photos location tags were added. As the number of geotagged photos increases, more applications will emerge, Wilson says. To stimulate this development, Flickr has released a kit that allows software engineers to build their own applications that include Flickr’s geotagging tools.

Indeed, geotagged Flickr photos could contribute to a project from Microsoft Research and the University of Washington, in which researchers have developed an algorithm that can stitch together disparate photos to create a seamless virtual tour of places like the Eiffel Tower in Paris. A collection of accurately geotagged photos from Flickr could benefit this project, says Suman Nath, a Microsoft researcher who works on a real-time mapping project called SenseWeb (see “Microsoft’s Plan to Map the World in Real Time”). Pictures that have the same geographic location can be manipulated by algorithms that “merge those images,” he says. “You can make a three-dimensional tour using all that information.”

Privacy issues remain a concern, however, with the increasing popularity of geotagging. Flickr’s Butterfield and his team have added some features to allow varying degrees of disclosure for pictures and geographical information. For instance, pictures can be either publicly visible or viewable only by some people. Additionally, a person has to actively add a geotag, and it can be private even if the picture itself is public. “One of the aspects of this that we’ve thought quite a bit about is privacy,” Butterfield says.

The Flickr team is looking for ways to improve other aspects of the service, too. For example, with a time-based search, people can look for pictures taken on a specific day, or images of a location taken at different times of year. And, as Yahoo improves its maps, geotagging through Flickr will become more feasible in places outside the United States.

Butterfield predicts that geotagging will continue to gain momentum as more cameras and camera-equipped cell phones come with global positioning systems that automatically tag a picture with its longitude and latitude. In addition, he says, software developers and cell-phone service providers are making it easier to share photos and upload them to the Internet. “In many ways we’re on the edge,” he says. “Over the next couple of years, we’ll see a lot more connectivity.”