GEE

The British GEE system was developed during World War II. GEE used a series of transmitters sending out precisely timed signals, and the aircraft using GEE, RAF Bomber Command's heavy bombers, examined the time of arrival on an oscilloscope at the navigator's station. If the signal from two stations arrived at the same time, the aircraft must be an equal distance from both transmitters, allowing the navigator to determine a line of position on his chart of all the positions at that distance from both stations. By making similar measurements with other stations, additional lines of position can be produced, leading to a fix. GEE was accurate to about 165 yards (150 m) at short ranges, and up to a mile (1.6km) at longer ranges over Germany. Used after WWII as late as the 1960s in the RAF (approx freq was by then 68MHZ).