December 1, 2008 Computer scientists designed a program that can analyze a photograph to identify where it was taken. The program scans the scene on the photo, noting colors, textures and lines, and uses these elements to compare it to more than six million images previously tagged with locations on online databases. The program has an average success rate of 16 percent, which is better than random chance or a human guess.
A picture may be worth a thousand words -- but years after it’s snapped, it may be tough to tell where in the world that photo was taken. To solve the problem, researchers have devised the first computer program that can analyze a single photo and fill in the blanks.
Computer scientists at Carnegie Mellon University in Pittsburgh, Pa., designed the program. First, they upload the image. The computer scans the scene and takes note of color, texture and lines -- things the human eye can't always perceive. Then, the computer compares its results to more than 6 million digital photos already tagged with locations on the digital-image-sharing website Flickr.
"It does well on landmark images, things that are very recognizable, like the Eiffel Tower or Tiananmen Square," said James Hays, a computer scientist at Carnegie Mellon.
The program also does well on geographic locations that have a unique look, like the deserts of the American Southwest. Computer scientists tested the program on a set of 200 photos.
"It succeeds about 16 percent of the time," Hays said. That number may sound low, but researchers say it's 30-times better than chance and better than the average person taking an educated guess. They also say the rates will improve as people continue to upload and share their photos in cyberspace, giving the program more data to pull from.
Computer scientists say the program could eventually be used in forensic investigations by detectives or in the military.
ABOUT GPS: The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use a combination of signals to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.
WHAT ARE PIXELS: "Pixel" is short for picture element, and represents a single point in a graphic image. Graphics monitors display images by dividing the screen into thousands (or millions) of pixels, arranged in rows and columns. A megapixel equals one million pixels. Pixels are a measure of digital image quality: the more pixels, the better. The modern digital camera works on the same principle as a conventional camera, but instead of focusing light onto a piece of film, it focuses it onto an image sensor array -- called a charged coupled device (CCD) -- made of tiny light-sensitive diodes that convert light into electrical charges. It turns the fluctuating waves of light (analog data) into bits of digital computer data. The more sensors that are packed onto the CCD's surface, the higher the pixel count, and the higher the resolution of the final image.
The Optical Society of America contributed to the information contained in the TV portion of this report.