where was this picture taken?

This is fascinating.

Two researchers at Carnegie Mellon University have figured out an algorithm that can detect where a picture has been taken, with an accuracy that's 30 times better than that of chance or random guesses. And their geolocation method may not be what you'd expect.

You'd think the best way to tell where a photo was shot would be to check for important buildings, landmarks in nature, or any signposts. Not so. Alexei A. Efros, assistant professor of computer science, and James Hays, a CS graduate student, developed their program to analyze the composition of photographs by creating and scanning histograms of image properties. Their algorithm examines the full profile of color and texture in each image, and also looks at various line features and geometric patterns. Then, it groups images of unknown location with images that have known details, and the geographical matching begins. www.io9.com