Loran

A system of electronic navigation in which a vessel or aircraft determines its latitude and longitude by measuring the time differences between low frequency radio transmissions from two stationary transmitters (slaves) and a stationary master transmitter. Contrary to the name, Loran is a medium range system, usually effective for no more than a few hundred miles from shore. The first commercial system was called Loran A; the latest (and final) development is Loran C.