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Sonobuoys
A sonobuoy (a portmanteau of sonar and buoy) is a relatively small buoy – typically diameter and long – expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic research. Theory of operation Sonobuoys are ejected from aircraft in canisters and deploy upon water impact. An inflatable surface float with a radio transmitter remains on the surface for communication with the aircraft, while one or more hydrophone sensors and stabilizing equipment descend below the surface to a selected depth that is variable, depending on environmental conditions and the search pattern. The buoy relays acoustic information from its hydrophone(s) via UHF/ VHF radio to operators on board the aircraft. History With the technological improvement of the submarine in modern warfare, the need for an effective tracking system was born. Sound Navigation And Ranging (SONAR) was originally developed by the British—who call ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonobuoy Deployment
A sonobuoy (a portmanteau of sonar and buoy) is a relatively small buoy – typically diameter and long – expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic research. Theory of operation Sonobuoys are ejected from aircraft in canisters and deploy upon water impact. An inflatable surface float with a radio transmitter remains on the surface for communication with the aircraft, while one or more hydrophone sensors and stabilizing equipment descend below the surface to a selected depth that is variable, depending on environmental conditions and the search pattern. The buoy relays acoustic information from its hydrophone(s) via UHF/ VHF radio to operators on board the aircraft. History With the technological improvement of the submarine in modern warfare, the need for an effective tracking system was born. Sound Navigation And Ranging (SONAR) was originally developed by the British—who cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoy
A buoy () is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Types Navigational buoys * Race course marker buoys are used for buoy racing, the most prevalent form of yacht racing and power boat racing. They delimit the course and must be passed to a specified side. They are also used in underwater orienteering competitions. * Emergency wreck buoys provide a clear and unambiguous means of temporarily marking new wrecks, typically for the first 24–72 hours. They are coloured in an equal number of blue and yellow vertical stripes and fitted with an alternating blue and yellow flashing light. They were implemented following collisions in the Dover Strait in 2002 when vessels struck the new wreck of the . * Ice marking buoys mark holes in frozen lakes and rivers so snowmobiles do not drive over the holes. * Large Navigational Buoys (LNB, or Lanby buoys) are automatic buoys over 10 m high equipped with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAF Coastal Command During World War II
RAF Coastal Command was a formation within the Royal Air Force (RAF). Founded in 1936, it was to act as the RAF maritime arm, after the Fleet Air Arm became part of the Royal Navy in 1937. Naval aviation was neglected in the inter-war period, 1919–1939, and as a consequence the service did not receive the resources it needed to develop properly or efficiently. This continued until the outbreak of the Second World War, during which it came to prominence. Owing to the Air Ministry's concentration on RAF Fighter Command and RAF Bomber Command, Coastal Command was often referred to as the "Cinderella Service", a phrase first used by the First Lord of the Admiralty at the time A V Alexander. Its primary task was to protect convoys from the German ''Kriegsmarine''s U-boat force. It also protected Allied shipping from the aerial threat posed by the '' Luftwaffe''. The main operations of Coastal Command were defensive, defending supplies lines in the various theatres of wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-frequency Direction Finding
High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over long distances; for example, between U-boats and their land-based headquarters. HF/DF was primarily used to catch enemy radios while they transmitted, although it was also used to locate friendly aircraft as a navigation aid. The basic technique remains in use to this day as one of the fundamental disciplines of signals intelligence, although typically incorporated into a larger suite of radio systems and radars instead of being a stand-alone system. Earlier systems used a mechanically rotated antenna or solenoid and an operator listening for peaks or nulls in the signal, which often took considerable time to determine the bearing on the order of a minute or more. Later systems used a set of antennas to receive the same signal in slightly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds. Radar was developed secretly for military use by several countries in the period before and during World War II. A key development was the cavity magnetron in the United Kingdom, which allowed the creation of relatively small systems with sub-meter resolution. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hodder & Stoughton
Hodder & Stoughton is a British publishing house, now an imprint (trade name), imprint of Hachette (publisher), Hachette. History Early history The firm has its origins in the 1840s, with Matthew Hodder's employment, aged 14, with Messrs Jackson and Walford, the official publisher for the Congregational church, Congregational Union. In 1861 the firm became Jackson, Walford and Hodder; but in 1868 Jackson and Walford retired, and Thomas Wilberforce Stoughton joined the firm, creating Hodder & Stoughton. Hodder & Stoughton published both religious and secular works, and its religious list contained some progressive titles. These included George Adam Smith, George Adam Smith's ''Isaiah'' for its ''Expositor’s Bible'' series, which was one of the earliest texts to identify multiple authorship in the Book of Isaiah. There was also a sympathetic ''Life of Francis of Assisi, St Francis'' by Paul Sabatier (theologian), Paul Sabatier, a French Protestant pastor. Matthew Hodder ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U-boat
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role (commerce raiding) and enforcing a naval blockade against enemy shipping. The primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from Canada and other parts of the British Empire, and from the United States, to the United Kingdom and (during the Second World War) to the Soviet Union and the Allied territories in the Mediterranean. German submarines also destroyed Brazilian merchant ships during World War II, causing Brazil to declare war on both Germany and Italy on 22 August 1942. The term is an anglicised version of the German word ''U-Boot'' , a shortening of ''Unterseeboot'' ('under-sea-boat'), though the German term refers to any submarine. Austro-Hungarian Navy submarines were also kno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulation
In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle measurements at known points, rather than measuring distances to the point directly as in trilateration; the use of both angles and distance measurements is referred to as triangulateration. In computer vision Computer stereo vision and optical 3D measuring systems use this principle to determine the spatial dimensions and the geometry of an item. Basically, the configuration consists of two sensors observing the item. One of the sensors is typically a digital camera device, and the other one can also be a camera or a light projector. The projection centers of the sensors and the considered point on the object's surface define a (spatial) triangle. Within this triangle, the distance between the sensors is the base ''b'' and must be known. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrographic Survey
Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/offshore oil drilling and related activities. Strong emphasis is placed on soundings, shorelines, tides, currents, seabed and submerged obstructions that relate to the previously mentioned activities. The term ''hydrography'' is used synonymously to describe ''maritime cartography'', which in the final stages of the hydrographic process uses the raw data collected through hydrographic survey into information usable by the end user. Hydrography is collected under rules which vary depending on the acceptance authority. Traditionally conducted by ships with a sounding line or echo sounding, surveys are increasingly conducted with the aid of aircraft and sophisticated electronic sensor systems in shallow waters. Organizations National and International Maritime Hydrography Hydrographic offices evolved from n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Survey Ship
A survey vessel is any type of ship or boat that is used for underwater surveys, usually to collect data for mapping or planning underwater construction or mineral extraction. It is a type of research vessel, and may be designed for the purpose, modified for the purpose or temporarily put into the service as a vessel of opportunity, and may be crewed, remotely operated, or autonomous. The size and equipment vary to suit the task and availability. Role The task of survey vessels is to map the bottom, and measure the characteristics of the benthic zone, full water column, and surface for the purpose of: * hydrography, the measurement and description of the physical features of oceans and other natural bodies of water, and the prediction of their change over time, for the primary purpose of safety of navigation and in support of other activities associated with those bodies of water, * general oceanography, the scientific study of the oceans, * mapping of marine habitats as part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Acoustic Ranging
Radio acoustic ranging, occasionally written as "radio-acoustic ranging" and sometimes abbreviated RAR, was a method for determining a ship's precise location at sea by detonating an explosive charge underwater near the ship, detecting the arrival of the underwater sound waves at remote locations, and radioing the time of arrival of the sound waves at the remote stations to the ship, allowing the ship's crew to use true range multilateration to determine the ship's position. Developed by the United States Coast and Geodetic Survey in 1923 and 1924 for use in accurately fixing the position of survey ships during hydrographic survey operations, it was the first navigation technique in human history other than dead reckoning that did not require visual observation of a landmark, marker, light, or celestial body, and the first non-visual means to provide precise positions. First employed operationally in 1924, radio acoustic ranging remained in use until 1944, when new radio navigat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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