an electronic navigational system used in airplanes, guided missiles, etc., in which signals are sent to a pair of ground transponders whose answering signals allow the aircraft's precise position to be determined
See Shoran in American Heritage Dictionary 4
(shôrˈănˌ, shōrˈ-)
noun
A relatively short-range navigation system by which a ship or aircraft can determine its position with high precision by measuring the times required for a radar signal to reach and return from each of two ground stations of known position.