GEE (navigation)
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GEE (short for "Grid" and pronounced simply as "G") or AMES Type 7000 was a British radio navigation system used during World War II; the ideas in GEE were developed by the Americans into the LORAN system.
LORAN was used by the US Navy and Royal Navy during World War II, and after the war came into common civilian use world-wide for coastal navigation, until GPS made it obsolete.
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Technical details
GEE used a series of broadcasters sending out precicely timed signals; the aircraft using GEE, 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, allowing the navigator to draw a line on his map of all the positions at that distance from both stations. Similarly, a difference in the arrival times indicated that the aircraft was closer to one station than the other; the actual difference denoted a particular hyperbola along which the aircraft must lie. By making similar measurements with other stations additional lines could be produced, leading to a fix.
Service history
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 became a routine problem about five months after GEE came into widespread use. However, the jamming was only effective over Europe, so aircraft still used GEE for navigation near their bases.
Stations
Eastern chain
The Eastern chain operated from 22 June 1941. The master station was at Daventry. Other stations included Ventnor and Stenigot.
Northern chain
The Northern GEE chain operated from late 1942 until March 1946 [1] (http://www.radarpages.co.uk/mob/navaids/gee/gee1.htm). The master and monitor stations were on Burifa Hill on Dunnet Head, in Caithness, Scotland.
Slave stations included:
- Scousburgh, Shetland Islands
- Windyhead Hill, near Fraserburgh
- Sango, Cape Wrath
Further reading
- Alfred Price, Instruments of Darkness: The History of Electronic Warfare (Peninsula, Los Altos, 1977) pp. 98–104
- R. V. Jones, The Wizard War: British Scientific Intelligence 1939–1945 (Coward, McCann and Geoghegan, New York, 1978) pp. 217–222
- Brian Johnson, The Secret War (BBC, London, Methuen, New York, 1978) pp. 84–89
External links
- Radio navigation systems (http://www.vectorsite.net/ttwiza.html); information and explanation relating to GEE.
- Imperial War Museam page (http://www.duxfordradiosociety.org/restoration/restoredequip/r1355/r1355.html); information about restored GEE receivers.
- Radarpages.co.uk page (http://www.radarpages.co.uk/mob/navaids/gee/gee1.htm); information about the mechanics of the system.