"Anyone who has used a Global Positioning System (GPS) navigator has seen the system's ability to tell you precisely where you are — and, most likely, has faced frustration when the device just doesn't work. Yet for the military — which uses GPS data for such mission-critical applications as target tracking, missile guidance, and simply getting around in foreign areas — GPS failure can be a matter of life or death. That's why military researchers, such as those at the Air Force Institute of Technology (AFIT) at Wright-Patterson Air Force Base in Ohio, have long been exploring alternatives to the Global Positioning System."

Continue reading a Communications of the ACM article that features an interview with Dr. Humphreys.