ALOK JHA Carbon Diem' inventors claim that, by using GPS to measure the speed and pattern of movement, their algorithm can identify the mode of transport being used. It can therefore calculate the amount of carbon dioxide that a journey has emitted into the atmosphere Keeping track of your carbon footprint could become as simple as slipping a mobile phone in your pocket: a London-based start-up company has developed software for mobile phones that uses global positioning satellites to work out automatically whether you are walking, driving or flying and then calculate your impact on the environment. Carbon Diem