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Decca Navigator System
The Decca Navigator System was a hyperbolic navigation, hyperbolic radio navigation system which 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 low frequency signals between 70 and 129 kilohertz, kHz, as opposed to pulse timing systems like Gee (navigation), Gee and LORAN. 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 cathode ray tube and highly skilled operator. The system was invented in the U.S., but development was carried out by Decca Radar, Decca in the UK. It was first deployed by the Royal Navy during World War II for the vital task of clearing the minefields to enable the D-Day 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 li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accuracy Of Navigation Systems
Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value'', while ''precision'' is how close the measurements are to each other. In other words, ''precision'' is a description of '' random errors'', a measure of statistical variability. ''Accuracy'' has two definitions: # More commonly, it is a description of only '' systematic errors'', a measure of statistical bias of a given measure of central tendency; low accuracy causes a difference between a result and a true value; ISO calls this ''trueness''. # Alternatively, ISO defines accuracy as describing a combination of both types of observational error (random and systematic), so high accuracy requires both high precision and high trueness. In the first, more common definition of "accuracy" above, the concept is independent of "precision", so a particular set of data can be said to be accurate, precise, both, o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver. The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was lau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decca Records
Decca Records is a British record label established in 1929 by Edward Lewis (Decca), Edward Lewis. Its U.S. label was established in late 1934 by Lewis, Jack Kapp, American Decca's first president, and Milton Rackmil, who later became American Decca's president. In 1937, anticipating Nazi Germany, Nazi aggression leading to World War II, Lewis sold American Decca and the link between the U.K. and U.S. Decca labels was broken for several decades. The British label was renowned for its development of recording methods, while the American company developed the concept of cast albums in the musical genre. Both wings are now part of the Universal Music Group. The U.S. Decca label was the foundation company that evolved into UMG (Universal Music Group). Label name The name dates back to a portable phonograph, gramophone called the "Decca Dulcephone" patented in 1914 by musical instrument makers Barnett Samuel and Sons. The name "Decca" was coined by Wilfred S. Samuel by merging the w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuberculosis
Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in which case it is known as latent tuberculosis. Around 10% of latent infections progress to active disease which, if left untreated, kill about half of those affected. Typical symptoms of active TB are chronic cough with blood-containing mucus, fever, night sweats, and weight loss. It was historically referred to as consumption due to the weight loss associated with the disease. Infection of other organs can cause a wide range of symptoms. Tuberculosis is spread from one person to the next through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with Latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. Diagnosis of active TB is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decca Navigator Mk 21
Decca may refer to: Music * Decca Records or Decca Music Group, a record label * Decca Gold, a classical music record label owned by Universal Music Group * Decca Broadway, a musical theater record label * Decca Studios, a recording facility in West Hampstead, England * London Decca, a maker of turntable tonearms and cartridges * Decca tree, a microphone recording system * The Deccas, a guitar-based band from Medway, England * Mpundi Decca, Congolese guitarist Other * '' Decca: The Letters of Jessica Mitford'', a 2006 book by Jessica Mitford * Decca Navigator System, a defunct marine and aeronautical navigation system * Decca Radar, later Racal-Decca Marine, a defunct marine electronics manufacturer * Decca Sports Ground, a cricket ground in London, England * Decca, old spelling of Dhaka, capital of Bangladesh See also * Deca (other) The Defense Commissary Agency (DeCA), headquartered at Fort Lee (Virginia), is an agency of the United States Department of Defense (DoD) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skywave
In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances. It is mostly used in the shortwave frequency bands. As a result of skywave propagation, a signal from a distant AM broadcasting station, a shortwave station, or – during sporadic E propagation conditions (principally during the summer months in both hemispheres) a distant VHF FM or TV station – can sometimes be received as clearly as local stations. Most long-distance shortwave (high frequency) radio communication – between 3 and 30 MHz – is a result of skywave propagation. Since the early 1920s amateur radio operators (or "hams"), limited to lower transmitter power than broadcast stations, have ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Admiralty Chart No 1607 Thames Estuary Southern Part, Published 1967
Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings *Admiralty, Trafalgar Square, a pub in London *Admiralty, Saint Petersburg, Russia * Admiralteyskaya (Saint Petersburg Metro), a metro station in Saint Petersburg, Russia, the name means "Admiralty" *Admiralty Arch in London, England *Admiralty House, London *Admiralty House, Sydney * Dutch Admiralty, a group of follies at Tsarskoye Selo, Russia *Former Admiralty House, Singapore Law * Admiralty court * Admiralty law, also called Maritime Law * Amirauté (New France) Naval organizations *Admiralty (navy), a governmental and/or naval body responsible for the administration of a navy Germany * German Imperial Admiralty, ''Kaiserliche Admiralität'' * German Imperial Admiralty Staff, ''Admiralstab'' Netherlands *Admiralty of Amsterdam *Admiralty of Friesl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Least Common Multiple
In arithmetic and number theory, the least common multiple, lowest common multiple, or smallest common multiple of two integers ''a'' and ''b'', usually denoted by lcm(''a'', ''b''), is the smallest positive integer that is divisible by both ''a'' and ''b''. Since division of integers by zero is undefined, this definition has meaning only if ''a'' and ''b'' are both different from zero. However, some authors define lcm(''a'',0) as 0 for all ''a'', since 0 is the only common multiple of ''a'' and 0. The lcm is the "lowest common denominator" (lcd) that can be used before fractions can be added, subtracted or compared. The least common multiple of more than two integers ''a'', ''b'', ''c'', . . . , usually denoted by lcm(''a'', ''b'', ''c'', . . .), is also well defined: It is the smallest positive integer that is divisible by each of ''a'', ''b'', ''c'', . . . Overview A multiple of a number is the product of that number and an integer. For example, 10 is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase-locked Loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a variable frequency oscillator and a phase detector in a feedback loop. The oscillator's frequency and phase are controlled proportionally by an applied voltage, hence the term voltage-controlled oscillator (VCO). The oscillator generates a periodic signal of a specific frequency, and the phase detector compares the phase of that signal with the phase of the input periodic signal, to adjust the oscillator to keep the phases matched. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same. Consequently, in addition to synchronizing signals, a phase-locked loop can track an input frequency, or it can generate a frequency that is a multiple of the input frequency. These properties are use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautical Chart
A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land (topographic map), natural features of the seabed, details of the coastline, navigational hazards, locations of natural and human-made aids to navigation, information on tides and currents, local details of the Earth's magnetic field, and human-made structures such as harbours, buildings, and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper (raster navigational charts) or computerized electronic navigational charts. Recent technologies have made available paper charts which are printed "on demand" with cartographic data that has been downloaded to the commercial printing company as recently as the night before printing. With each daily download, critica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lines Of Position
A position line or line of position (LOP) is a line (or, on the surface of the earth, a curve) that can be both identified on a chart (nautical chart or aeronautical chart) and translated to the surface of the earth. The intersection of a minimum of two position lines is a fix that is used in position fixing to identify a navigator's location. There are several types of position line: * Compass bearing – the angle between north and the line passing through the compass and the point of interest * Transit – a line passing through the observer and two other reference points * Leading line – the line passing through two marks indicating a safe channel * Leading lights – the line passing through two beacons indicating a safe channel * Sector lights – the lines created by masked colored lights that indicate a safe channel See also * Coordinate line * Intersection (aeronautics) * Navigation * Position circle * Sight reduction In astronavigation, sight reduction is the proces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperbola
In mathematics, a hyperbola (; pl. hyperbolas or hyperbolae ; adj. hyperbolic ) is a type of smooth curve lying in a plane, defined by its geometric properties or by equations for which it is the solution set. A hyperbola has two pieces, called connected components or branches, that are mirror images of each other and resemble two infinite bows. The hyperbola is one of the three kinds of conic section, formed by the intersection of a plane and a double cone. (The other conic sections are the parabola and the ellipse. A circle is a special case of an ellipse.) If the plane intersects both halves of the double cone but does not pass through the apex of the cones, then the conic is a hyperbola. Hyperbolas arise in many ways: * as the curve representing the reciprocal function y(x) = 1/x in the Cartesian plane, * as the path followed by the shadow of the tip of a sundial, * as the shape of an open orbit (as distinct from a closed elliptical orbit), such as the orbit of a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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