A DME based area navigation systems for GPS/WAAS interference mitigation in general aviation applications

The Federal Aviation Administration is leading the National Airspace System modernization effort, in part by supplanting traditional air traffic services with GPS aided by the wide and local area augmentation systems (WAAS & LAAS). Making GPS the sole-means of navigation will enhance safety, flexibility and efficiency of operations for all aircraft ranging from the single engine general aviation aircraft to the complex commercial jet-liners. This transformation of the National Airspace System will be gradual and the build-up to a sole-means GPS capability is expected to occur concurrently with the de-commissioning of a significant number of existing ground-based navigational facilities. Temporary interruptions of GPS services due to intentional or unintentional interference during this transition period could present significant problems for general aviation aircraft. To successfully deal with such outage scenarios, this paper discusses the use of an existing radio-navigation aid, the distance measuring equipment (DME), to provide a redundant navigation system alongside GPS/WAAS during this phase out period. Specifically, a system that fuses a low-end DME receiver with low cost dead-reckoning sensors (inertial, air-data and magnetometers) is shown to provide an affordable area navigation capability for general aviation users. The justification for choosing DME over other ground based navigational aids is discussed. This back-up system allows a reduction of the number of operational radio-navigation aids required while still providing adequate coverage for navigation during the transition to a sole-means GPS National Airspace System.