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For more technology stories, visit newscientist.com/technology 6 August 2011 | NewScientist | 23 Mass sway reveals risk of a crushing crowd A CROWD crush at the Love Parade music festival in Duisburg, Germany, last year killed 21 people and injured over 500 others. The disaster might have been avoided if security personnel at the festival had been able to detect the dangerous crowd build-up, but monitoring the behaviour of thousands of festival- goers is no easy task. A new system aims to detect congestion hotspots, guiding security to disperse a crowd before tragedy can strike. Barbara Krausz at the Fraunhofer Institute for Intelligent Analysis and Information Systems in Sankt Augustin, Germany, developed the system based on one simple observation: when people become trapped in a highly congested area, they sway slowly from side to side in an effort to keep their balance. Software detects this motion by analysing the movement of each pixel between different frames of crowd video footage – highly symmetrical pixel motions indicate swaying. “It does not recognise that there is a person, we just check the pixels,” she says. Any sudden increase in symmetrical movements suggests there may be a congestion problem, but it could also be the result of something unusual in the crowd. The system highlights such areas in red, allowing event organisers to quickly investigate the problem. When applied to the available footage of the Love Parade, Krausz’s system highlighted areas where people squeezed together as emergency vehicles made routine patrols through the crowds. The system produced its highest alert about half an hour before the disaster – the last moment for which Krausz analysed data. Simply knowing about a congestion problem doesn’t solve it, of course. Krausz hopes a future version of her system could run crowd simulations to tell security personnel the best course of action, like opening a gate at a given location. She will present the work at the Advanced Video and Signal-Based Surveillance conference in Klagenfurt, Austria, next month. Anders Johansson, a researcher in crowd modelling at University College London, says that the move from individual tracking to whole-crowd models is promising. “You cannot replace humans altogether, but to give attention to certain areas that seem to be developing in dangerous ways is useful,” he says. Jacob Aron n “When people become trapped in a highly congested area, they sway slowly from side to side” –Channelled into a dead end– ERIK WIFFERS/AFP/GETTY Solar skylight takes the heat off Even in an air-conditioned office, sitting near a window with direct sunlight can get pretty toasty. Now a skylight that captures the boiling rays to make electricity could keep the heat out. Developed by Enfocus, based in Hayward, California, the device is made of an array of glass lenses that concentrate direct sunlight onto narrow, opaque strips of photovoltaic cells made of gallium arsenide and germanium. Diffuse light passes through the edges of the lens, providing even illumination for a room. Company founder Jason Lu claims the cells could provide more electricity than regular solar cells and save further on costs in glass-walled buildings by providing natural light while curbing excess heating. Fishing for faces on Facebook It may be time to adjust your Facebook profile image: a picture of your face taken on the street, say, could be all it takes for strangers to access a wealth of personal information. Alessandro Acquisti at Carnegie Mellon University in Pittsburgh, Pennsylvania, and colleagues used Google-owned facial recognition software to match people with their Facebook profiles, providing names, birth dates and other demographics for 1 in 3 test subjects. He then used this information to predict the first five digits of their Social Security numbers. Meeting like-minded people online Ever wondered if anyone’s spending time poring over your personal web page, or reading the same news articles as you? You may soon be able to find out. Whoislive, a new internet plug-in, lets you interact with any other users who are visiting the same web page as you. The idea is for every web page to become a live chat room where like-minded visitors can share and socialise. Only those who are signed up to Whoislive will be visible on each web page, but you can invite your friends to join the service. If successful, it could spell the end of dedicated “comments” sections. ONE PER CENT FANCY/PLAINPICTURE For breaking tech news go to: newscientist.com/onepercent
