Editing Decca Navigator System (section)

=== Commercial deployment ===
[[File:DECCA unit, NMS.jpg|thumb|Decca receiver, Mk.51 seen in the [[National Museum of Scotland]]]]
After the end of [[World War II]] the Decca Navigator Co. Ltd. was formed (1945) and the system expanded rapidly, particularly in areas of [[British Empire|British influence]]; at its peak it was deployed in many of the world's major shipping areas. More than 15,000 receiving sets were in use aboard ships in 1970. There were 4 chains around England, 1 in Ireland and 2 in Scotland, 12 in Scandinavia (5 each in Norway and Sweden and 1 each in Denmark and Finland), a further 4 elsewhere in northern Europe and 2 in Spain.

Canada was another early user, with branch offices set up in [[Toronto]] in 1953.<ref>{{cite web |url=https://canada-company.com/c/402478-decca-navigator-canada-ltd |title=Corporation Information |website=Decca Navigator (Canada) Ltd. |publisher=Canada Company Directory}}</ref>{{failed verification|date=June 2022|reason=This source does not support the statement}} The first chain was installed in southwest [[Newfoundland]] in 1956 as part of a joint Canada-US Navy surveying program. This led to commercial deployments the next year in [[Nova Scotia]] and an inland system for air traffic in the busy [[Quebec City]]-[[Montreal]] area. A fourth chain covering eastern Newfoundland was added in 1958. When meetings in Montreal in 1958 led to VOR and DME being selected as the standard aviation navigation systems, the Montreal system was moved eastward to cover the [[Anticosti Island]] area of the [[Gulf of St. Lawrence]], and the western Newfoundland chain was later repositioned to better cover the [[Cabot Strait]]. A series of chains was also proposed to cover the [[Northwest Passage]] had oil tanker traffic used the area, but this never came to be. Another was briefly set up covering [[Lake Ontario]] in 1971 for the [[International Field Year for the Great Lakes]].<ref>{{cite magazine |magazine= Decca Navigator News |date=September 1976 |title= Decca Marine Canada}}</ref> The last Canadian chain shut down in 1986, after Loran-C became widespread.

In the late 1950s an experimental Decca chain was set up in the United States, in the New York area, to be used for navigating the [[Boeing Vertol CH-46 Sea Knight|Vertol 107]] helicopters of [[New York Airways]]. These helicopters were operating from the principal local airports—[[John F. Kennedy International Airport|Idlewild Airport]] on Long Island, [[Newark Liberty International Airport|Newark Airport]] in New Jersey, [[LaGuardia Airport]] in the Borough of Queens, nearer to Manhattan, and a site on the top of the (then) [[MetLife Building|PanAm Building]] on Park Avenue. Use of Decca was essential because its signals could be received down to sea level, were not subject to the line-of-sight limitations of [[VHF omnidirectional range|VOR]]/[[Distance measuring equipment|DME]] and did not suffer the slant-range errors that create problems with VOR/DME close to the transmitters. The Decca installations in the New York Airways helicopters included the unique Decca 'roller map' displays that enabled the pilot to see his or her position at a glance, a concept infeasible with VOR/DME.

This chain installation was considered highly controversial at the time, for political reasons. This led to the U.S. Coast Guard, under instructions from the Treasury Department to which it reported, banning the use of Decca receivers in ships entering New York harbour for fear that the system might create a de facto standard (as it had become in other areas of the world). It also served to protect the marketing interests of the Hoffman Electronics division of ITT, a principal supplier of VOR/DME systems, that Decca might have been poised to usurp.

This situation was exacerbated by the workload problems of the Air Traffic Controllers Association (ATCA), under its executive director Francis McDermott, whose members were forced to use radar data on aircraft positions, relaying those positions by radio to the aircraft from their control locations. An example of the problem, cited by experts, was the [[1960 New York mid-air collision|collision of a Douglas DC8 and a Lockheed Constellation over Staten Island, New York]],<ref>{{Cite web |title=UNITED AIR LINES, INC, DC-8, N 8013U, AND TRANS WORLD AIRLINES, INC., CONSTELLATION 1049A, N 6907C, NEAR STATEN ISLAND, NEW YORK, DECEMBER 16, 1960 |website=Plane and Train Wrecks {{!}} Online Collections |url=https://planeandtrainwrecks.com/Document?db=DOT-AIRPLANEACCIDENTS&query=(select+0+(byhits+(eq+ACCIDENT_DATE+%601960%2F12%2F16))) |access-date=2022-06-17}}</ref> that—according to some experts—could have been avoided if the aircraft had been Decca-equipped and could not only have determined their positions more precisely but would not have suffered from the rho-theta position errors inherent in VOR/DME.

Other chains were established in Japan (6 chains); Namibia and South Africa (5 chains); India and Bangladesh (4 chains); North-West Australia (2 chains); the [[Persian Gulf]] (1 chain with stations in Qatar and the United Arab Emirates and a second chain in the north of the Gulf with stations in Iran) and the Bahamas (1 chain). Four chains were planned for Nigeria but only two were built and these did not enter into public service. Two chains in Vietnam were used during the [[Vietnam War]] for helicopter navigation, with limited success.
During the Cold War period, following WWII, the R.A.F. established a confidential chain in Germany. The Master station was in [[Bad Iburg]] near Osnabrück and there were two Slaves. The purpose of this chain was to provide accurate air navigation for the corridor between Western Germany and Berlin in the event that a mass evacuation of allied personnel may be required. In order to maintain secrecy, frequencies were changed at irregular intervals.