April 19, 2007 Imagine the United States attempting to fight a war if the Global Positioning System (GPS) were suddenly unavailable. The U.S. Defense Advanced Research Projects Agency (DARPA) has obviously thought about it has just awarded a concept development contract to a team of corporations led by Boeing. The objective of the Robust Surface Navigation (RSN) program is to develop technologies that can exploit various "signals of opportunity" -- electronic waves emanating from satellites, cell phone towers and even television transmission towers -- to provide precise location and navigation information to ground troops when GPS signals are being electronically jammed or blocked by natural or man-made obstacles, such as foliage or buildings. The team includes ROSUM, the only company that has used broadcast television signals to locate mobile assets. It's also the first company to combine television and GPS signals for truly robust situational awareness in all environments.