Xcode and OpenGL software
Acrossair’s app employs augmented-reality technology to overlay directions to the nearest subway station in real-time on a smartphone screen. Pointed down, the screen displays arrows to all available subway lines from that starting point; held at eye level, signs to the nearest lines (including information such as walking distance, possible destinations, etc.) are overlaid on the actual street view on the screen, stacked according to distance. Acrossair’s app is currently available for several cities’ subway systems, including New York, London, Tokyo, and Madrid.