GEE (NAVIGATION)
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×'GEE' or 'AMES Type 7000' was a British radio navigation system used by the Royal Air Force during World War II. GEE was designed to improve aircraft navigation accuracy, thereby increasing the destructiveness of raids by Avro Lancasters and various other bombers.
The technology of GEE was 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.
Gee was a hyperbolic navigation system, like the OMEGA Navigation System and the current-day LORAN-C.
GEE transmitters sent out precisely timed pulses. There were three Gee stations, one master and two slaves. The master sent a pulse followed two milliseconds later by a double pulse. The first slave station sent a single pulse one millisecond after the master's single pulse, and the second slave sent a single pulse one millisecond after the master's double pulse. The whole cycle repeated on a four millisecond cycle. On board the aircraft, the signals from the three stations were received. The on board equipment would display the two slaves' signals as blips on an oscilloscope type display. Since the display timing was controlled by the pulses from the master station, the display equipment gave the difference in reception time of the pulses and hence the relative distance from the master and each slave. The aircraft carried a navigation chart with several hyperbolae plotted on it. Each hyperbolic line represented a line of constant time difference for the master and one slave station. All the navigator had to do was find the intersection of the two hyperbolae representing the two slave stations.
During the development phase, a trial Gee set was on board a Vickers Wellington flying over occupied Europe. The aircraft crashed, and although the equipment was not fitted with demolition charges, the British couldn't be sure that the set wouldn't be studied by the Germans. It subsequently appeared that the Germans completely missed it.
R. V. Jones took charge of the attempts to hide the existence of the system. First he forbade the use of the codename 'Gee' in any signal traffic, but instead, false signals were sent referring to a non existent system called 'Jay' (it was hoped that the similarity would cause confusion). Next he had a number of extra aerials (antennae) added to the Gee transmitters radiating false signals. He then arranged for a couple of RAF personnel to talk 'carelessly' in a restaurant about how 'Jay' was in fact a complete copy of the German Knickebein system and also arranged for this to be reported via the Double Cross system to add credence (and just in case no-one was listening). Finally, he arranged for false Knickebein signals to be transmitted over Germany. All of this appealed to Jones's flair for practical joking.
The ruse worked better than he could have hoped. The Germans spent many months trying to jam the Knickebein signals unable to fathom out why their jamming was completely ineffective. It was nearly seven months before the Germans finally realised that they were jamming signals that were not being received, and that the British were using a completely different system. It was several more months before effective jamming was achieved. Gee was highly susceptible to jamming. All the Germans had to do was radiate surplus pulses. The British were amazed that the system remained unmolested for as long as it did - three months was the best that they could normally expect. The German jamming was only effective over their occupied territory, and Gee remained perfectly usable over Britain.
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 radiated in all directions, 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 bombers' positions to night fighters. The aircraft receivers themselves were designated "ARI 5033" in GEE Mk.I and "ARI 5083" in GEE Mk.II.
The Eastern chain operated from 22 June 1942. The master station was at Daventry, Northamptonshire. ()
The monitor station was RAF Barkway[1][2][3], near Royston, Hertfordshire. ()
Other stations included
★ Clee Hill, Shropshire ()
★ Stenigot ()
★ Gibbet Hill, Hindhead, Surrey ()
The Northern GEE chain operated from late 1942 until March 1946 [1]. The master and monitor stations were on Burifa Hill on Dunnet Head, in Caithness, Scotland. ()
Slave stations included:
★ Scousburgh, Shetland Islands ()
★ Windyhead Hill, Pennan, Aberdeenshire ()
★ Sango, Durness, Sutherland ()
★ Master Sharpitor ()
★ Slave B Worth Matravers ()
★ Slave C Sennen ()
★ Slave D Folly ()
★ Chain Monitor Trerew () [2]
A chain of Gee stations was opened after the war in North Germany. Stations were at Winterberg, Ibug, Nordhorn and Uchte. Ex members of the RAF who served on this chain have their own website at www.rafwinterberg.co.uk.
Worth Matravers was used after the war as a training base for gee operators.
★ 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
★ Colin Latham and Anne Stobbs, ''Radar, A Wartime Miracle'' (Sutton Publishing Ltd, Stroud, Gloucestershire 1996) ISBN 0750916431
★ Radio Navigation Systems in Greg Goebel's THE WIZARD WAR
★ Imperial War Museum page; information about restored GEE receivers.
★ Radarpages.co.uk page; information about the mechanics of the system.
★ History of RAF Wintenberg and North German Gee chain
★ THE GEE SYSTEM by W. F. BLANCHARD including 1948 map
1. English Heritage
2. English Heritage
3. Geograph
GEE control bays
GEE transmitter
GEE airborne equipment
The technology of GEE was 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.
| Contents |
| Technical details |
| The System almost Compromised |
| Service history |
| Stations |
| Eastern chain |
| Northern chain |
| South Western Chain |
| Further reading |
| External links |
| See also |
Technical details
Gee was a hyperbolic navigation system, like the OMEGA Navigation System and the current-day LORAN-C.
GEE transmitters sent out precisely timed pulses. There were three Gee stations, one master and two slaves. The master sent a pulse followed two milliseconds later by a double pulse. The first slave station sent a single pulse one millisecond after the master's single pulse, and the second slave sent a single pulse one millisecond after the master's double pulse. The whole cycle repeated on a four millisecond cycle. On board the aircraft, the signals from the three stations were received. The on board equipment would display the two slaves' signals as blips on an oscilloscope type display. Since the display timing was controlled by the pulses from the master station, the display equipment gave the difference in reception time of the pulses and hence the relative distance from the master and each slave. The aircraft carried a navigation chart with several hyperbolae plotted on it. Each hyperbolic line represented a line of constant time difference for the master and one slave station. All the navigator had to do was find the intersection of the two hyperbolae representing the two slave stations.
The System almost Compromised
During the development phase, a trial Gee set was on board a Vickers Wellington flying over occupied Europe. The aircraft crashed, and although the equipment was not fitted with demolition charges, the British couldn't be sure that the set wouldn't be studied by the Germans. It subsequently appeared that the Germans completely missed it.
R. V. Jones took charge of the attempts to hide the existence of the system. First he forbade the use of the codename 'Gee' in any signal traffic, but instead, false signals were sent referring to a non existent system called 'Jay' (it was hoped that the similarity would cause confusion). Next he had a number of extra aerials (antennae) added to the Gee transmitters radiating false signals. He then arranged for a couple of RAF personnel to talk 'carelessly' in a restaurant about how 'Jay' was in fact a complete copy of the German Knickebein system and also arranged for this to be reported via the Double Cross system to add credence (and just in case no-one was listening). Finally, he arranged for false Knickebein signals to be transmitted over Germany. All of this appealed to Jones's flair for practical joking.
The ruse worked better than he could have hoped. The Germans spent many months trying to jam the Knickebein signals unable to fathom out why their jamming was completely ineffective. It was nearly seven months before the Germans finally realised that they were jamming signals that were not being received, and that the British were using a completely different system. It was several more months before effective jamming was achieved. Gee was highly susceptible to jamming. All the Germans had to do was radiate surplus pulses. The British were amazed that the system remained unmolested for as long as it did - three months was the best that they could normally expect. The German jamming was only effective over their occupied territory, and Gee remained perfectly usable over Britain.
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 radiated in all directions, 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 bombers' positions to night fighters. The aircraft receivers themselves were designated "ARI 5033" in GEE Mk.I and "ARI 5083" in GEE Mk.II.
Stations
Eastern chain
The Eastern chain operated from 22 June 1942. The master station was at Daventry, Northamptonshire. ()
The monitor station was RAF Barkway[1][2][3], near Royston, Hertfordshire. ()
Other stations included
★ Clee Hill, Shropshire ()
★ Stenigot ()
★ Gibbet Hill, Hindhead, Surrey ()
Northern chain
The Northern GEE chain operated from late 1942 until March 1946 [1]. The master and monitor stations were on Burifa Hill on Dunnet Head, in Caithness, Scotland. ()
Slave stations included:
★ Scousburgh, Shetland Islands ()
★ Windyhead Hill, Pennan, Aberdeenshire ()
★ Sango, Durness, Sutherland ()
South Western Chain
★ Master Sharpitor ()
★ Slave B Worth Matravers ()
★ Slave C Sennen ()
★ Slave D Folly ()
★ Chain Monitor Trerew () [2]
A chain of Gee stations was opened after the war in North Germany. Stations were at Winterberg, Ibug, Nordhorn and Uchte. Ex members of the RAF who served on this chain have their own website at www.rafwinterberg.co.uk.
Worth Matravers was used after the war as a training base for gee operators.
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
★ Colin Latham and Anne Stobbs, ''Radar, A Wartime Miracle'' (Sutton Publishing Ltd, Stroud, Gloucestershire 1996) ISBN 0750916431
External links
★ Radio Navigation Systems in Greg Goebel's THE WIZARD WAR
★ Imperial War Museum page; information about restored GEE receivers.
★ Radarpages.co.uk page; information about the mechanics of the system.
★ History of RAF Wintenberg and North German Gee chain
★ THE GEE SYSTEM by W. F. BLANCHARD including 1948 map
1. English Heritage
2. English Heritage
3. Geograph
See also
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