A new system that counts shoppers and track their movements through stores by staring at their shoes could provide a helpful marketing tool – without the privacy invasion of analysing CCTV images. Stephan Richter and colleagues at the Hasso Plattner Institute in Potsdam, Germany, came up with the idea while working on a way to help software distinguish people gathered round large tabletop touchscreen computers. The computer tends to struggle to keep track of who is doing what if people move around the screen while working.

To solve this, the team developed a system called Bootstrapper which works out who's standing where using a downward-facing Kinect camera to recognise their shoes. By measuring how a shoe distorts the infrared grid projected by Kinect's depth camera, Bootstrapper acquires unique, high-resolution 3D images of each person's footwear. The team found that the system has an accuracy of 96 percent and will present their work at the Computer Human Interaction conference in Austin, Texas, in May.