Decca Navigator System - Knowledge (XXG)

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Decca Flight Log moving map display to further improve ease of navigation. In spite of these advantages, the RTCA ultimately chose VOR/DME for two primary reasons; VOR offered coverage over about the same range as Decca, about 200 miles, but did so with a single transmitter instead of Decca's four, and Decca's frequencies proved susceptible to interference from static due to lightning, while VOR's higher frequencies were not quite as sensitive.

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180 transmitting stations using "chains" of three or four transmitters each to allow position fixing by plotting intersecting electronic lines. Decca's primary use was for ship navigation in coastal waters, offering much better accuracy than the competing LORAN system. Fishing vessels were major post-war users, but it was also used on some aircraft, including a very early (1949) application of

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several advancements in the art that would prove useful. He initially imagined the system being used for aircraft testing, specifically the accurate calculation of ground speed. Some experiments were carried out in California in 1938, selecting frequencies with harmonic "beats" that would allow for station identification in a network of transmitters. Both the

765:; 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. 289:, the difference in phase between the two signals is constant along a hyperbolic path. If two stations transmit on the same frequency, it is impossible for the receiver to separate them. Instead, each chain was allocated a nominal frequency, known as 1f, and each station in the chain transmitted at a harmonic of this base frequency, as follows: 1026:

as much energy as normal chain stations. Given that the length of the chain baselines did not change, and were relatively short, at long distance the signal offered almost no accuracy. Instead, Dectra operated as a track system; aircraft would navigate by keeping themselves within the signal defined by a particular Decca lane.

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A further application of the Decca system was implemented by the U.S. Navy in the late 1950s and early 1960s for use in the Tongue of the Ocean/Eleuthera Sound area near The Bahamas, separating the islands of Andros and New Providence. The application was for sonar studies made possible by the unique

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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.

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As well as transmitting the Decca frequencies of 5f, 6f, 8f and 9f, an 8.2f signal, known as Orange, was also transmitted. The beat frequency between the 8.0f (Red) and 8.2f (Orange) signals allowed a 0.2f signal to be derived and so resulted in a hyperbolic pattern in which one cycle (360°) of phase

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The lanes were numbered 0 to 23 for red, 30 to 47 for green and 50 to 79 for purple. The zones were labelled A to J, repeating after J. A Decca position coordinate could thus be written: Red I 16.30; Green D 35.80. Later receivers incorporated a microprocessor and displayed a position in latitude and

485:, with 18 green, 24 red, or 30 purple lanes in each zone. This meant that on the baseline (the straight line between the Master and its Slave) the zone width was the same for all three patterns of a given chain. Typical lane and zone widths on the baseline are shown in the table below (for chain 5B): 1025:

Unlike the Delrac system, Dectra was essentially the normal Decca Navigator system with the modification of several existing transmitter sites. These were located at the East Newfoundland and Scottish chains, which were equipped with larger antennas and high-power transmitters, broadcasting 20 times

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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

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that indicated the phase difference for each pattern. Each Decometer drove a second indicator that counted the number of lanes traversed – each 360 degrees of phase difference was one lane traversed. In this way, assuming the point of departure was known, a more or less distinct location could

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Receivers determined their location by measuring the phase difference from two or more of the patterns from the displays. They could then look at the chart to find where the two closest charted hyperbolas crossed. The accuracy of this measurement was improved by choosing the set of two patterns that

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system that ultimately won the competition offered navigation over perhaps a 200-mile radius, and could not offer a solution to the long-distance problem. Additionally, as the Decca system provided an X and Y location, as opposed to the angle-and-range VOR/DME, Decca proposed offering it with their

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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

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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

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difference of the signals from the master and one of the secondaries, produced a relative phase measure that was presented on a clock-like display. The phase difference was caused by the relative distance between the stations as seen by the receiver. As the receiver moves these distances change and

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Another application was developed by the Bendix Pacific division of Bendix Corporation, with offices in North Hollywood, California, but not deployed: PFNS—Personal Field Navigation System—that would enable individual soldiers to ascertain their geographic position, long before this capability was

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landings. The Allied forces needed an accurate system not known to the Germans and thus free of jamming. After the war, it came off the secret list and was commercially developed by the Decca Company and deployed around UK and later used in many areas around the world. At its peak there were about

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The nominally continuous wave transmissions were in fact divided into a 20-second cycle, with each station in turn simultaneously transmitting all four Decca frequencies (5f, 6f, 8f and 9f) in a phase-coherent relationship for a brief period of 0.45 seconds each cycle. This transmission, known as

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The 'low frequency' signalling of the Decca system also permitted its use on submarines. One 'enhancement' of the Decca system was to offer the potential of keying the signal, using Morse code, to signal the onset of nuclear war. This option was never taken up by the UK government. Messages were

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An interesting characteristic of the Decca VLF signal discovered on BOAC, later British Airways, test flights to Moscow, was that the carrier switching could not be detected even though the carrier could be received with sufficient strength to provide navigation. Such testing, involving civilian

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A significant amount of income from the Decca system was due to the receivers being leased to users, not sold outright. This guaranteed predictable annual income. When the patents on the original technology lapsed in the early 1980s, new receivers were quickly built by a number of companies. In

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area to verify receiver accuracy. In the car installation, it was found possible to navigate within an individual traffic lane. The company entertained high hopes that the system could be used in aircraft, to permit much more precise navigation in the critical airspace around airports and urban

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for detailed mapping and surveying of coasts and harbours. The Hi-Fix equipment was leased for a period with temporary chains established to provide coverage of the area required, Hi-Fix was commercialised by Racal Survey in the early 1980s. An experimental chain was installed with coverage of

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that put his career on hold for a period of two years. During this period he had the idea of position fixing by means of phase comparison of continuous wave transmissions. This was not the first such system, but O'Brien apparently developed his version without knowledge of the others, and made

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this range and accuracy may appear poor, in its day the Decca system was one of the few, if not the only, position fixing system available to many mariners. Since the need for an accurate position is less when the vessel is further from land, the reduced accuracy at long ranges was not a great

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By day these errors could range from a few meters on the baseline up to a nautical mile at the edge of coverage. At night, skywave errors were greater and, on receivers without multipulse capabilities, it was not unusual for the position to jump a lane, sometimes without the navigator knowing.

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and three (occasionally two) secondary stations, termed Red, Green and Purple. Ideally, the secondaries would be positioned at the vertices of an equilateral triangle with the master at the centre. The baseline length, that is, the master-secondary distance, was typically 60–120 nautical miles

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in January 1944 to test a wide variety of upgrades and production equipment. By this time the competing Gee system was known to the Admiralty and the two systems were tested head-to-head under the code names QM and QH. QM was found to have better sea-level range and accuracy, which led to its

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effort, began the process of introducing a standard long-range radio navigation system for aviation use. Decca proposed a system that could offer both high-accuracy at short ranges and trans-Atlantic navigation with less accuracy, using a single receiver. The system was known as

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system, was introduced in 1954, proposing 28 stations that provided worldwide coverage. The system was predicted to offer 10 miles (16,000 m) accuracy at 2,000 miles (3,200 km) range 95% of the time. Further development was ended in favour of the Dectra system.

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central London and receivers placed in London buses and other vehicles to demonstrate an early vehicle location and tracking system. Each vehicle would report its location automatically via a conventional VHF two-way radio link, the data added to a voice channel.

449:. Since the wavelength of the common frequency was small compared with the distance between the Master and Slave stations there were many possible lines of position for a given phase difference, and so a unique position could not be arrived at by this method. 853:

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.

861:, 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. 788:

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

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The main advantage of Dectra compared to other systems being proposed for the RTCA solution was that it could be used for both medium-range navigation over land, as well as long-range navigation over the Atlantic. In comparison, the

917:) introduced receivers that could be purchased outright, and were much smaller and easier to use than the current Decca counterparts. The "ap" versions directly output the longitude and latitude to two decimals (originally in datum 1038:

Decca continued to propose that Dectra be used for the long-range role. In 1967 they installed another transmitter in Iceland to provide ranging along the Scotland-Newfoundland track, with a second proposed to be installed on the

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system to civilian use in 1974 offered stiff competition, but Decca was well established by this time and continued operations to 2000. Decca Navigator was eventually replaced, along with Loran and similar systems, by the

909:, the UK weapons and communications company, acquired Decca in 1980. Merging Decca's radar assets with their own, Racal began selling off the other portions of the company, including avionics and Decca Navigator. 131:

The display panel of a Decca Navigator Mk 12 (ca. 1962). Decca position coordinates were directly displayed by four decometers and these were plotted on a conventional chart that had been over-printed with Decca

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only) instead of using the "deco meter" displays, offering accuracy better than ±9.3 m, much better than the Decca units. This also eliminated the need for the special charts printed with Decca lanes and zones.

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A more accurate system named Hi-Fix was developed using signalling in the 1.6 MHz range. It was used for specialised applications such as precision measurements involved with oil-drilling and by the

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Other receivers, typically for aeronautical applications, divided the transmitted frequencies down to the basic frequency (1f) for phase comparison, rather than multiplying them up to the LCM frequency.

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The phase difference between the signals received from stations A (Master) and B (Secondary) is constant along each hyperbolic curve. The foci of the hyperbolas are at the transmitting stations, A and B.

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in April 1943 at 70/130 kHz. It was decided that the original frequencies were not ideal, and a new system using a 14 kHz inter-signal spacing was selected. This led to the common 5, 6, 8 and

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It was phase comparison at this common frequency that resulted in the hyperbolic lines of position. The interval between two adjacent hyperbolas on which the signals are in phase was called a

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receivers. The receiver consisted of an electronics unit with two dials and was known to its operators as the "Blue Gasmeter Job". A Decca chain was set up, consisting of a master station at

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Decca sued ap for infringement and, in the ensuing court battle, Decca lost the monopoly. That signalled the beginning of the end for the company. Income dwindled and eventually, the UK

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During daylight, ranges of around 400 nautical miles (740 km) could be obtained, reducing at night to 200 to 250 nautical miles (460 km), depending on propagation conditions.

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system that allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison of two

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system, being carried out by Watt's group). However, in October 1941 the British Admiralty Signal Establishment (ASE) became interested in the system, which was then classified as

163:. This made it much easier to design receivers using 1940s electronics, and operation was simplified by giving a direct readout of Decca coordinates without the complexity of a 872:

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

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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

1043:. They also installed Dectra receivers with Omnitrac computers and a lightweight version of the Flight Log on a number of commercial airliners, notably a 1010: 840:

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

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The frequencies given are those for Chain 5B, known as the English Chain, but all chains used similar frequencies between 70 kHz and 129 kHz.

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provided an automatic method of lane and zone identification by using the same phase comparison techniques described above on lower frequency signals.

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in February/March 1944. The success of the trials and the relative ease of use and accuracy of the system resulted in Decca receiving an order for 27

1221:"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" 256:

If one selects a particular phase difference, say 30 degrees, and plots all the locations where that phase difference occurs, the result is a set of

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Multipulse, allowed the receiver to extract the 1f frequency and so to identify the lane that the receiver was in (to a resolution of a zone).

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Work on this concept continued, and in 1951 a modified version was presented that offered navigation over very wide areas. This was known as

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In the immediate post-war era, Decca began studying a long-range system like Decca, but using much lower frequencies to enable reception of

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Blanchard, Walter (September 1991). "Hyperbolic Airborne Radio Navigation Aids — A Navigator's View of their History and Development".

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Decca receivers multiplied the signals received from the Master and each Slave by different values to arrive at a common frequency (

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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

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clandestinely sent, however, between Decca stations thereby bypassing international telephone calls, especially in non-UK chains.

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The headquarters of Decca Navigator were at New Malden, Surrey, just off the Kingston by-pass. There was a Decca School, at

269:. As there were three secondaries there were three patterns, also termed Red, Green and Purple. The patterns were drawn on 1385: 641:

reviewed the system but he did not follow it up, deeming it too easily jammed (and likely due to the existing work on the

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in England. In 1939 O’Brien sent him details of the system so it could be put forward to the British military. Initially

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in 1956 as part of a joint Canada-US Navy surveying program. This led to commercial deployments the next year in

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and to sweep the minefields in the planned areas. The swept areas were marked with buoys in preparation for the

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The Decca Navigator - Principles and Performance of the System, The Decca Navigator Company Limited, July 1976

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The Decca Navigator System on D-Day, 6 June 1944, An Acid Test, Commander Hugh St. A. Malleson, R.N. (Ret.)

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Decca receiver Mk II from the 1980s that could be purchased instead of leased. It could store 25 waypoints.

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The Decca Navigator System consisted of individual groups of land-based radio transmitters organised into

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the Decca Navigator Co. Ltd. was formed (1945) and the system expanded rapidly, particularly in areas of

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had oil tanker traffic used the area, but this never came to be. Another was briefly set up covering

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A three-station trial was held in conjunction with a large-scale assault and landing exercise in the

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at long distances. In February 1946 the company proposed a system with two main stations located at

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Assuming that one's position was known to this accuracy, this gave an effectively unique position.

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Navigation Systems: A Survey of Modern Electronic Aids, ed. G.E. Beck, van Nostrand Reinhold, 1971

120: 1326: 1187: 978: 638: 188: 833: 802: 727: 286: 261: 1397: 1318: 1110: 992:, short for "Decca Long Range Area Cover". A further development, including features of the 837: 821: 790: 642: 164: 156: 144: 997: 966: 723: 466: 977:(today part of Canada). Together, these stations would provide navigation over the main 1423: 885: 762: 711: 270: 241: 604: 127: 1407: 1330: 940:

ceased Decca transmissions at midnight on 31 March 2000. The Irish chain provided by

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Night Passage to Normandy, Lieutenant-Commander Oliver Dawkins, R.N.V.R, Decca, 1969

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would provide general ranging information to measure progress along the main track.

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collision of a Douglas DC8 and a Lockheed Constellation over Staten Island, New York

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A ruling from the European Union forced the UK government to withdraw funding. The

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in the Borough of Queens, nearer to Manhattan, and a site on the top of the (then)

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and, on 5 June 1944, 17 of these ships used it to accurately navigate across the

869: 797:, and the western Newfoundland chain was later repositioned to better cover the 781: 777: 707: 691: 654: 171: 21: 677:-like extension, but never developed. A follow-up test was carried out in the 1322: 1064: 813:. The last Canadian chain shut down in 1986, after Loran-C became widespread. 746: 699: 175: 469:

Decca Chart of the Thames Estuary, marked with red and green lanes and zones.

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After the initial ship tests, Decca conducted tests in cars, driving in the

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those changes are represented by the movement of the hands on the displays.

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aircraft, is quite common and may well not be in the knowledge of a pilot.

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continued transmitting until 19 May 2000. Japan continued operating their

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resulted in the lines crossing at as close to a right angle as possible.

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Each station transmitted a continuous wave signal that, by comparing the

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Hyperbolic Radionavigation Systems, Compiled by Jerry Proc VE3FAB, 2007

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made possible by the satellite-based GPS (Global Positioning System).

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as part of the deception that the invasion would be focussed on the

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take responsibility for operating the system in the early 1990s.

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O’Brien's friend, Harvey F. Schwarz, was chief engineer of the

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Canada was another early user, with branch offices set up in

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particular, Aktieselskabet Dansk Philips ('Danish Philips',

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frequencies, used throughout the life of the Decca system. 7

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considered the idea too complicated and work ended in 1939.

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for the vital task of clearing the minefields to enable the

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chain until March 2001, the last Decca chain in operation.

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Decca Navigator Mk. 21, with the Decometer dials prominent.

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area. 21 minesweepers and other vessels were fitted with

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as a set of hyperbolic lines in the appropriate colour.

1295:"Dectra in Iceland", Decca Navigator News, October 1967 473:

Early Decca receivers were fitted with three rotating

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An example of the problem, cited by experts, was the

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of three or four stations. Each chain consisted of a

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Decca Navigator Spain by Santiago Insua (in Spanish)

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in 1953. The first chain was installed in southwest

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In 1936 William J. O'Brien, an engineer, contracted

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in 2000, when that became available for public use.

46:. Unsourced material may be challenged and removed. 1396:is available for free viewing and download at the 780:and an inland system for air traffic in the busy 649:. The first marine trials were conducted between 981:between London and New York. A third station in 710:. A fourth decoy transmitter was located in the 573:Angle of cut of the hyperbolic lines of position 358:, LCM) for each Master/Slave pair, as follows: 660:Further trials were conducted in the northern 191:. The system was deployed extensively in the 8: 811:International Field Year for the Great Lakes 1225:Plane and Train Wrecks | Online Collections 738:centres where traffic density was highest. 1011:Radio Technical Commission for Aeronautics 155:, as opposed to pulse timing systems like 1283: 1266: 1249: 1174: 1157: 195:and was used by helicopters operating to 170:The system was invented and developed by 106:Learn how and when to remove this message 487: 360: 291: 174:in the UK. It was first deployed by the 126: 119: 1386:Decca Navigator Station Zeven (Germany) 1147: 1054:began to be installed for these needs. 1337:A modified version is = Jerry Proc, 591:Although in the days of differential 7: 1376:A virtual tour of a Decca Main Chain 1371:Decca Navigator System by Jerry Proc 1076:characteristics of the ocean floor. 44:adding citations to reliable sources 750:Decca receiver, Mk.51 seen in the 285:When two stations transmit at the 14: 579:Propagation errors (for example, 202:The opening of the more accurate 281:Detailed principles of operation 20: 1393:STAFF FILM REPORT 66-19A (1966) 881:Decca, Racal, and the closedown 552:difference equates to 5 zones. 31:needs additional citations for 229:The Decca Navigator principle. 1: 167:and highly skilled operator. 1192:Decca Navigator (Canada) Ltd 971:Gander International Airport 938:general lighthouse authority 481:The lanes were grouped into 1194:. Canada Company Directory. 1052:inertial navigation systems 1022:, short for "Decca Track". 1013:(RTCA), as part of a wider 752:National Museum of Scotland 151:signals between 70 and 129 1440: 566:The accuracy depended on: 1323:10.1017/S0373463300010092 1311:The Journal of Navigation 1188:"Corporation Information" 1121:Omega (navigation system) 1126:Local positioning system 55:"Decca Navigator System" 1205:"Decca Marine Canada". 1099:Zeven DECCA-transmitter 1009:In the early 1960s the 929:stepped in, having the 215:Principles of operation 1419:Navigational equipment 1094:Puckeridge DECCA tower 931:lighthouse authorities 894: 754: 609: 470: 287:phase-locked frequency 233: 138:Decca Navigator System 133: 124: 927:Ministry of Transport 888: 749: 742:Commercial deployment 607: 464: 356:least common multiple 227: 130: 123: 1207:Decca Navigator News 1088:Special DECCA towers 795:Gulf of St. Lawrence 635:Decca Record company 523:Zones (all patterns) 40:improve this article 994:General Post Office 942:Bórd Iascaigh Mhara 720:Admiralty Outfit QM 696:Admiralty Outfit QM 673:was reserved for a 647:Admiralty Outfit QM 576:Instrumental errors 245:(110–220 km). 189:moving map displays 979:great circle route 952:Other applications 895: 755: 639:Robert Watson-Watt 610: 570:Width of the lanes 559:Range and accuracy 494:Width on Baseline 471: 234: 134: 125: 1341:, 14 January 2001 1209:. September 1976. 834:LaGuardia Airport 803:Northwest Passage 763:British influence 757:After the end of 728:Normandy Landings 530: 529: 443: 442: 379:Common Frequency 376:Master Multiplier 349: 348: 262:lines of position 116: 115: 108: 90: 1431: 1414:Radio navigation 1398:Internet Archive 1339:"The GEE System" 1334: 1296: 1293: 1287: 1281: 1270: 1264: 1253: 1247: 1236: 1235: 1233: 1231: 1217: 1211: 1210: 1202: 1196: 1195: 1184: 1178: 1172: 1161: 1155: 1111:GEE (navigation) 828:on Long Island, 826:Idlewild Airport 822:New York Airways 809:in 1971 for the 791:Anticosti Island 735:Kingston By-Pass 488: 370:Slave Multiplier 361: 301:Frequency (kHz) 292: 165:cathode ray tube 145:radio navigation 111: 104: 100: 97: 91: 89: 48: 24: 16: 1439: 1438: 1434: 1433: 1432: 1430: 1429: 1428: 1404: 1403: 1390:The short film 1367: 1308: 1305: 1300: 1299: 1294: 1290: 1282: 1273: 1265: 1256: 1248: 1239: 1229: 1227: 1219: 1218: 1214: 1204: 1203: 1199: 1186: 1185: 1181: 1173: 1164: 1156: 1149: 1144: 1139: 1107: 1090: 1060: 1007: 969:in Ireland and 967:Shannon Airport 959: 954: 883: 832:in New Jersey, 820:helicopters of 744: 724:English Channel 688: 615: 602: 561: 539: 478:be identified. 459: 457:Lanes and zones 373:Master Harmonic 283: 271:nautical charts 231: 222: 217: 112: 101: 95: 92: 49: 47: 37: 25: 12: 11: 5: 1437: 1435: 1427: 1426: 1421: 1416: 1406: 1405: 1402: 1401: 1388: 1383: 1378: 1373: 1366: 1365:External links 1363: 1362: 1361: 1358: 1353: 1350: 1347: 1344: 1343: 1342: 1304: 1301: 1298: 1297: 1288: 1286:, p. 305. 1284:Blanchard 1991 1271: 1269:, p. 304. 1267:Blanchard 1991 1254: 1252:, p. 303. 1250:Blanchard 1991 1237: 1212: 1197: 1179: 1177:, p. 302. 1175:Blanchard 1991 1162: 1160:, p. 301. 1158:Blanchard 1991 1146: 1145: 1143: 1140: 1138: 1135: 1134: 1133: 1128: 1123: 1118: 1113: 1106: 1103: 1102: 1101: 1096: 1089: 1086: 1059: 1056: 1006: 1003: 958: 955: 953: 950: 882: 879: 838:PanAm Building 830:Newark Airport 743: 740: 712:Thames Estuary 702:and slaves at 687: 686:D-Day landings 684: 614: 611: 601: 598: 585: 584: 577: 574: 571: 560: 557: 538: 535: 528: 527: 524: 520: 519: 516: 512: 511: 508: 504: 503: 500: 496: 495: 492: 458: 455: 441: 440: 437: 434: 431: 428: 425: 421: 420: 417: 414: 411: 408: 405: 401: 400: 397: 394: 391: 388: 385: 381: 380: 377: 374: 371: 368: 367:Slave Harmonic 365: 347: 346: 343: 340: 336: 335: 332: 329: 325: 324: 321: 318: 314: 313: 310: 307: 303: 302: 299: 296: 282: 279: 242:master station 221: 218: 216: 213: 114: 113: 28: 26: 19: 13: 10: 9: 6: 4: 3: 2: 1436: 1425: 1422: 1420: 1417: 1415: 1412: 1411: 1409: 1399: 1395: 1394: 1389: 1387: 1384: 1382: 1379: 1377: 1374: 1372: 1369: 1368: 1364: 1359: 1357: 1354: 1351: 1348: 1345: 1340: 1336: 1335: 1332: 1328: 1324: 1320: 1316: 1312: 1307: 1306: 1302: 1292: 1289: 1285: 1280: 1278: 1276: 1272: 1268: 1263: 1261: 1259: 1255: 1251: 1246: 1244: 1242: 1238: 1226: 1222: 1216: 1213: 1208: 1201: 1198: 1193: 1189: 1183: 1180: 1176: 1171: 1169: 1167: 1163: 1159: 1154: 1152: 1148: 1141: 1136: 1132: 1129: 1127: 1124: 1122: 1119: 1117: 1114: 1112: 1109: 1108: 1104: 1100: 1097: 1095: 1092: 1091: 1087: 1085: 1081: 1077: 1073: 1069: 1066: 1057: 1055: 1053: 1049: 1046: 1042: 1036: 1033: 1027: 1023: 1021: 1016: 1012: 1004: 1002: 999: 995: 991: 986: 984: 980: 976: 972: 968: 964: 956: 951: 949: 947: 943: 939: 934: 932: 928: 923: 920: 916: 910: 908: 904: 900: 892: 887: 880: 878: 875: 871: 867: 862: 860: 854: 850: 847: 843: 839: 835: 831: 827: 823: 819: 814: 812: 808: 804: 800: 796: 792: 787: 783: 779: 775: 771: 766: 764: 760: 753: 748: 741: 739: 736: 731: 729: 725: 721: 717: 713: 709: 705: 701: 697: 693: 685: 683: 680: 676: 672: 668: 663: 658: 656: 652: 648: 644: 640: 636: 631: 629: 625: 620: 612: 606: 599: 597: 594: 589: 582: 578: 575: 572: 569: 568: 567: 564: 558: 556: 553: 549: 545: 543: 536: 534: 525: 522: 521: 517: 514: 513: 509: 506: 505: 501: 498: 497: 493: 490: 489: 486: 484: 479: 476: 468: 463: 456: 454: 450: 448: 438: 435: 432: 429: 426: 423: 422: 418: 415: 412: 409: 406: 403: 402: 398: 395: 392: 389: 386: 383: 382: 378: 375: 372: 369: 366: 363: 362: 359: 357: 352: 344: 341: 338: 337: 333: 330: 327: 326: 322: 319: 316: 315: 311: 308: 305: 304: 300: 297: 294: 293: 290: 288: 280: 278: 274: 272: 268: 264: 263: 259: 254: 251: 246: 243: 239: 230: 226: 219: 214: 212: 210: 205: 200: 198: 197:oil platforms 194: 190: 185: 181: 177: 173: 168: 166: 162: 158: 154: 150: 149:low frequency 146: 143: 139: 129: 122: 118: 110: 107: 99: 96:November 2011 88: 85: 81: 78: 74: 71: 67: 64: 60: 57: – 56: 52: 51:Find sources: 45: 41: 35: 34: 29:This article 27: 23: 18: 17: 1392: 1314: 1310: 1303:Bibliography 1291: 1228:. Retrieved 1224: 1215: 1206: 1200: 1191: 1182: 1082: 1078: 1074: 1070: 1061: 1048:Vickers VC10 1037: 1028: 1024: 1019: 1008: 989: 987: 975:Newfoundland 960: 935: 924: 914: 911: 896: 890: 866:Persian Gulf 863: 855: 851: 815: 807:Lake Ontario 799:Cabot Strait 793:area of the 774:Newfoundland 767: 759:World War II 756: 732: 719: 695: 689: 670: 666: 659: 646: 632: 619:tuberculosis 616: 590: 586: 565: 562: 554: 550: 546: 541: 540: 531: 491:Lane or Zone 482: 480: 474: 472: 451: 446: 444: 353: 350: 284: 275: 266: 260: 255: 247: 237: 235: 228: 201: 180:World War II 169: 137: 135: 117: 102: 93: 83: 76: 69: 62: 50: 38:Please help 33:verification 30: 877:intervals. 870:Vietnam War 782:Quebec City 778:Nova Scotia 708:Beachy Head 692:Moray Firth 655:Isle of Man 533:longitude. 499:Purple lane 1408:Categories 1137:References 1065:Royal Navy 818:Vertol 107 700:Chichester 682:adoption. 542:Multipulse 537:Multipulse 515:Green lane 475:Decometers 258:hyperbolic 176:Royal Navy 142:hyperbolic 66:newspapers 1331:130079994 1142:Citations 874:Bad Iburg 849:VOR/DME. 679:Irish Sea 662:Irish Sea 624:U.S. Army 596:problem. 467:Admiralty 265:called a 193:North Sea 132:lattices. 1131:Datatrak 1105:See also 963:skywaves 946:Hokkaidō 786:Montreal 653:and the 651:Anglesey 526:10563 m 518:586.8 m 510:440.1 m 507:Red lane 502:352.1 m 345:127.500 334:113.333 298:Harmonic 220:Overview 1230:17 June 1116:Loran-C 1032:VOR/DME 983:Bermuda 899:Brixham 770:Toronto 704:Swanage 675:Loran-C 613:Origins 600:History 581:Skywave 465:A 1967 364:Pattern 323:70.833 312:85.000 295:Station 267:pattern 204:Loran-C 178:during 80:scholar 1329: 1058:Hi-Fix 1041:Azores 1020:Dectra 1005:Dectra 990:Delrac 957:Delrac 716:Calais 384:Purple 317:Purple 306:Master 238:chains 140:was a 82: 75: 68: 61: 53: 1424:Decca 1327:S2CID 1317:(3). 907:Racal 903:Devon 483:zones 424:Green 339:Green 250:phase 184:D-Day 172:Decca 161:LORAN 87:JSTOR 73:books 1232:2022 1045:BOAC 1015:ICAO 998:POPI 919:ED50 706:and 628:Navy 626:and 447:lane 439:18f 419:24f 399:30f 159:and 136:The 59:news 1319:doi 996:'s 973:in 889:An 846:DME 842:VOR 643:Gee 593:GPS 404:Red 328:Red 209:GPS 157:Gee 153:kHz 42:by 1410:: 1325:. 1315:44 1313:. 1274:^ 1257:^ 1240:^ 1223:. 1190:. 1165:^ 1150:^ 915:ap 901:, 891:ap 730:. 436:×3 433:6f 430:×2 427:9f 416:×4 413:6f 410:×3 407:8f 396:×5 393:6f 390:×6 387:5f 342:9f 331:8f 320:5f 309:6f 199:. 1400:. 1333:. 1321:: 1234:. 844:/ 784:- 671:f 667:f 665:9 583:) 109:) 103:( 98:) 94:( 84:· 77:· 70:· 63:· 36:.

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