DOD has not established specific guidance describing what constitutes a military, geodetic referenced, sole means air navigation capability. The use of geodetic referenced navigation systems in the sole means mode is not a new concept. This includes enroute, terminal, and non-precision approach (up to the published decision height and range minimums) for any specific landing independent and without the aid of any other navigation system or mission computer. Accurate radio bearing (radials) and ranging to a specific radio beacon are used to generate steering signals with sufficient accuracy to enable a pilot to perform safe flight. Both of these systems are station referenced rather than geodetic referenced systems. TACAN and VOR/DME are qualified as sole means air navigation systems.
Except for limited testing of Loran-C, previous testing of geodetic systems has not dealt with qualifying the entire system as a sole means air navigation system. GPS and the other geodetic positioning systems require a random area navigation (RNAV) computer associated with the basic sensor, to provide navigation and steering information to the pilot. The GPS L-Band signal will be available on a world wide basis 24 hours a day. The primary differences are associated with the propagation of their carrier frequency and the inherent accuracy that is obtainable from each.
OMEGA, Loran-C, and TRANSIT are all geodetic referenced positioning systems that permit navigation in much the same manner as GPS. In order to accomplish this the GPS replacement system must demonstrate that it is capable of meeting or exceeding the performance and key characteristics of the present systems. The DOD navigation goal is to phase out the use of the existing TACAN, VOR/DME, OMEG4, Loran-C, and TRANSIT when GPS becomes fully operational and integrated in military aircraft, ships and ground units. Criteria for Military Certification of GPS for Sole Means Air NavigationĮdward C.
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