Gee (navigation) - Definition

GEE was a British radio navigation system used during World War II. It used a series of broadcasters sending out precicely timed signals, and the aircraft using GEE, Bomber Command's heavy bombers, examined the time of arrival on an osciloscope 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, allowing the navigator to draw a line on his map of all the positions at that distance from both stations. By making similar measurements with other stations additional lines can be produced, leading to a fix. GEE entered service in March 1942 and was accurate to about 165 yards at short ranges, and up to a mile at longer ranges over Germany. At its extreme range, which was about 400 miles it had an accuracy of 2 miles. Unlike the German beam systems where the bombers flew to their targets along the beam, the GEE pulses were not directional, so even if detected, they would not reveal the bombers' likely destinations. As the system was passive, unlike H2S, there were no return signals which could give away the bomber's positions to night fighters. However the system was open to jamming which after few month this became a routine problem.

The ideas in GEE were developed by the Americans into the LORAN system and was used by the US and Royal Navys during World War II.