New photo recognition software on a remote server works out precisely where you are from a digital-camera image and sends back directions that will get you to your destination.

When their system receives an image, it begins by identifying vertical and horizontal lines. Next, it warps the image so that the horizontals are all parallel with each other, and the same for verticals. This transforms the picture into one that was taken square on, rather than at an angle.

The software then looks for useful features, such as the corners of windows and doors, and extracts the colors and intensities of the pixels around them. Next, it searches the image database for matching data, using the base station that the cellphone’s signal came from as a guide. Finally, it uses the differences between the two images to calculate the photographer’s position within one meter.