Boat Cover Article Owning a boat is a matter of pride. For many, buying a boat is a lifetime achievement and something that you and your family will enjoy thoroughly during holidays and family get-togethers. A boat is a wonderful place to celebrate a special occasion too with friends and loved ones. It's a fantastic way to enjoy the beauty of the outdoors. However, in order to keep the boat in order you will need to provide it with proper maintenance and care. This is where you will find using of a boat cover to be invaluable to keep your boat protected and secure. The purpose of a boat cover is to protect the boat from the outside environment and the ever-changing weather conditions. If it is left unattended and uncovered a boat will, as any object left in the open, succumb to corrosion and wear and tear caused by the elements. You will be surprised to know that a properly fit boat cover can prolong the longevity of a boat by up to 50 percent, as compared to a boat which goes uncovered. There are many, many types of boat covers on the market. The type of boat cover that best suits your boat will depend upon the make and model of the boat, the amount of time the boat will be unattended, and the type of weather your boat will be exposed to a majority of the time. The best boat cover would be that which allows complete coverage. It should be form fitting with correctly positioned slits to accommodate the mast, rails and other such things. This is why many people prefer customized boat covers which form fit and account for each nuance on the boat, giving it a snug fit. There are many different fabrics that are popular for making boat covers. The best boat covers tend to be made using waver polyester alternated with non-waver polyester. Canvas is another popular type of fabric that is used extensively because of its' resistance to wear. Typically, the more rugged the boat cover the better. People who leave their boat unattended for long periods of time would benefit from the thicker, more rugged covers. Boaters who tend to their boats more frequently may find that a thinner version is more convenient. It is very important to remember that the boat cover you choose should be totally waterproof. There are many hi-tech materials available today which will allow for any moisture accumulation to evaporate more easily and more quickly. Some covers are also very strong when it comes to protection from the harm of ultraviolet rays which can be equally as damaging as moisture. Before you make your decision on selecting a boat cover, place a value judgment on cost vs. the quality of protection. Take into account the elements your boat will be exposed to and then choose the cover that best fills your needs at the best price. The useful life of your boat can be dependent on your boat cover choice.
BRIDGE The bridge of a ship is an area or room from which the ship can be commanded. When a ship is underway, the ship's captain or a senior officer is on the bridge at all times to maintain command and control. [edit] Evolution Traditionally, in sailing ships, the ship would be commanded from the poop deck, right aft. With the arrival of paddle steamers, engineers required a platform from which they could inspect the paddle wheels and the captain required a position where his view would not be obstructed by the paddle houses. A raised walkway, literally a bridge, connecting the paddle houses was therefore provided. When the screw propeller superseded the paddle wheel, the bridge was retained. Traditionally, commands would be passed from the senior officer on the bridge to stations dispersed throughout the ship, where physical control of the ship was exercised, as technology did not exist for the remote control of e.g. steering or machinery. Helm orders would be passed to an enclosed wheel house, where the coxswain or helmsman operated the ship's wheel. Engine commands would be relayed to the engineer in the engine room by an engine telegraph, which displayed the captain's orders on a dial. The engineer would ensure that the correct combination of steam pressure and engine revolutions were applied to enact his orders. The bridge was often open to the elements, therefore a weatherproof pilot house could be provided, from where a pilot (traditionally, the pilot was the ship's navigating officer) could issue commands from shelter. The compass platform of a British destroyer in the Battle of the Atlantic during the Second World War. Notice the binnacle in the prominent position centrally and the voice pipes for relaying commands. The armoured wheelhouse and the coxswain would be directly underneath. The Royal Navy favoured the open bridge for the unique tactical view it gave the Captain, long after other navies had moved indoors.Iron, and later steel, ships also required a compass platform. This was usually a tower, where a magnetic compass could be sited as far away from the ferrous interference from the hulk the ship. Depending upon the design and layout of a ship, all of these terms can be variously interchangeable. Larger ships, particularly warships, often had a number of different bridges. A navigation bridge would be used for the actual conning of the ship. A separate Admiral's bridge could be provided in flagships, where the Admiral could exercise strategic control over his fleet without interfering with the Captain's tactical command of the vessel. In older warships, a heavily-armoured conning tower was often provided, where the vital command staff could be located under protection to ensure that the ship could be commanded and fought under fire. Modern advances in remote control equipment has seen progressive transfer of the actual control of the ship to the bridge. The wheel and throttles can be operated directly from the bridge, directly controlling often-unmanned machinery spaces.
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BULKHEAD A bulkhead is an upright wall within the hull of a ship. Other kinds of partition elements within a ship are decks and deckheads. Bulkheads in a ship serve several purposes: They increase the structural rigidity of the vessel, divide functional areas into rooms and create watertight compartments that can contain water in the case of a hull breach or other leak. When equipped with purpose-designed fireproofing, bulkheads and decks are able to achieve fire-resistance ratings in an effort to achieve compartmentalisation, which is a passive fire protection measure, subject to stringent bounding. Openings in fire-resistance rated bulkheads and decks must be firestopped to restore the fire-resistance ratings that would otherwise be compromised, if the openings were left unsealed. The Authority Having Jurisdiction for such measures varies depending upon the flag of the ship. Merchant vessels are typically subject to the regulations and inspections of the Coast Guards of the flag country. Combat ships are subject to the regulations set out by the navy of the country that owns the ship. Combat ships may also be equipped to have its bulkheads and decks fully grounded (electrically), as a countermeasure against EMI and EMP damage, resulting from nuclear or Electromagnetic bomb detonations near the ship, which could otherwise severely damage the electronic systems on a ship, thus negating its combat power. In the case of firestops, cable jacketing is typically removed within the seal and firestop rubber modules are internally fitted with copper shields, which contact the cables' armour in order to ground the seal. There are also conductive fill materials in use for that purpose, which must be in direct contact with cable armour to ensure full grounding of the bulkheads and decks. Any openings that are not fully grounded would defeat that purpose. The word bulki meant "cargo" in Old Norse. The Song Dynasty Chinese author Zhu Yu wrote of Chinese ships with watertight bulkhead compartments in his book Pingzhou Table Talks of 1119 AD. A Chinese trade ship dated to 1277 AD was found off the southern coast of China in 1973, and had 12 bulkhead compartment rooms in its hull. Sometime in the 15th century sailors and builders in Europe realized that walls within a vessel would prevent cargo from shifting during passage. In shipbuilding, any vertical panel was called a "head." So walls installed abeam (side-to-side) in a vessel's hull were called "bulkheads." Now, by extension, the term applies to every vertical panel aboard a ship, except for the hull itself. The term was later applied to other vehicles, such as trams, automobiles, aircraft or spacecraft, as well as to containers, such as fuel tanks. In some of these cases bulkheads are airtight to prevent air leakage or the spread of a fire.
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BUOY A buoy is a floating device that can have many different purposes, which determine whether the buoy is anchored (stationary) or allowed to drift. The word is most commonly pronounced ([b??]) (as in buoyant), but in American English it is often pronounced [?bu.i]. Contents [hide] 1 Types 2 Other uses 3 Gallery 4 See also 5 References 6 External links [edit] Types Sea mark - aids pilotage by marking a maritime channel, hazard and administrative area to allow boats and ships to navigate safely. Lifebuoy - used as a life saving buoy designed to be thrown to a person in the water to provide buoyancy. Usually has a connecting line allowing the casualty to be pulled to the rescuer Submarine communication buoys - used for release in case of emergencies or for communication Communication buoy for a bottom pressure sensor, for tsunami detection. DAN buoy - has two meanings: a large maritime navigational aid providing a platform for light and radio beacons a lifebuoy with a flags used on yachts and smaller pleasure craft Sonobuoy - used by anti-submarine warfare aircraft to detect submarines by SONAR Surface Marker Buoy - taken on dives by scuba divers to mark their position underwater Decompression buoy - deployed by submerged scuba divers to mark their position underwater whilst doing decompression stops shot buoy - used to mark dive sites for the boat safety cover of scuba divers so that the divers can descend to the dive site more easily in conditions of low visibility or tidal currents and more safely do decompression stops on their ascent Mooring buoys - used to keep one end of a mooring cable or chain on the water's surface so that ships or boats can tie on to it Tripping buoys - used to keep one end of a 'tripping line' on the water's surface so that a stuck anchor can more easily be freed Weather buoys - equipped to measure weather parameters such as air temperature, barometric pressure, wind speed and direction and to report these data via satellite radio links to meteorological centres for use in forecasting and climate study. May be anchored (moored buoys) or allowed to drift (drifting buoys) in the open ocean currents. Position is calculated by the satellite. Tsunami buoys - anchored buoys that can detect sudden changes in undersea water pressure are used as part of tsunami warning systems in the Pacific and Indian Oceans. Profiling buoy - specialised models which adjusts its buoyancy so that it will sink at a controlled rate to 2,000 metres below the surface while measuring sea temperatures and salinity. Then after typically 10 days it returns to the surface and transmits its data via satellite before sinking again. Ice marking buoys - used for marking ice holes in frozen lakes and rivers, so that snowmobiles do not drive over the holes. Marker buoys - used in naval warfare, particularly anti-submarine warfare, is a light-emitting or smoke-emitting, or both, marker using some kind of pyrotechnic to provide the flare and smoke. It is commonly a 3-inch (76 mm) diameter device about 20 inches (500 mm) long that is set off by contact with seawater and floats on the surface. Some markers extinguish after a set period and others are made to sink. Lobster trap buoys - brightly colored buoys used for the marking of lobster trap locations so the person lobster fishing can find their lobster traps. Each lobster fisherman has his or her own color markings so they know which one is theirs. They are only allowed to haul their own traps and must display their buoy color on their boat so law enforcement officials know what they should be hauling. The buoys are brightly colored so they can be seen under conditions when there is poor visiblity like rain, fog, sea smoke, etc. Waverider buoy - used to measure the movement of the water surface as a wave train. The wave train is analysed to determine statistics like the significant wave height and period, and wave direction. Target buoy - used to simulate target (like small boat) in live fire exercise by naval and coastal forces, usually targeted by weapons (medium size) like HMG's, rapid fire cannons (20 or so mm), autocannons (bigger ones up to 40 and 57mm) and also anti-tank rockets.
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CABIN A cabin is an enclosed room generally on a ship or an aircraft. [edit] Sailing ships In sailing ships, the officers and paying passengers would have an individual or shared cabin. The commanding officer also known as the captain would have the grand cabin that normally spanned the stern with large windows, subdivided with movable panels that could be taken down in time of battle so that a small gun could be set up there or the large room used as an operating theatre. [edit] Modern warships In most modern warships the commanding officer has a main cabin, often adjacent to the ship's central control room (operations room), and a sea cabin adjacent to the bridge. Thus, when likely to be called from sleep or attending to administration, the CO can be at the Bridge or Ops room instantly. In the Star Trek science fiction series, the sea cabin has become the ready room which amply describes its relationship to the bridge and the captain's use of it. Officers will normally have their own cabins, which doubles as their office. Some senior non-commissioned officers may have a cabin for similar reasons. [edit] Passenger ships A Sky suite onboard the Celebrity cruise ship Constellation.In ships carrying passengers, they are normally accommodated in cabins, taking the terminology familiar to seafarers and so adding mystique to a voyage.
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CAPSTAN A capstan is a rotating machine used to apply force to another element, notably used on board ship and on dock walls, for heaving-in or veering ropes, cables, and hawsers. In its earliest form, the capstan consisted of a timber mounted vertically through a vessel's structure which was free to rotate. Levers, known as handspikes, were inserted through holes at the top of the timber and used to turn the capstan. A rope wrapped several turns around the drum was thus hauled upon. A rudimentary ratchet was provided to hold the tension. The ropes were always wound in a clockwise direction (seen from above). Capstans evolved to consist of a wooden drum or barrel mounted on an iron axle. Two barrels on a common axle were used frequently to allow men on two decks to apply force to the handspikes. Later capstans were made entirely of iron, with gearing in the head providing a mechanical advantage when the handspikes were pushed counterclockwise. One form of capstan was connected by a shaft and gears to an anchor windlass on the deck below. Modern capstans are powered electrically, hydraulically, pneumatically, or via an internal combustion engine. Typically a gearbox is used which trades reduced speed, relative to the prime mover, for increased torque. A capstan differs from a windlass, which is used for similar purposes, in having the axis on which the rope is wound vertical instead of horizontal. In yachting terminology, winches function on the same principle as capstans, though in industrial applications, the term winch generally implies a machine which stores the rope on a drum. The word, connected with the Old French capestan or cabestan(t), from Old Provençal cabestan, from capestre "pulley cord,", from Latin capistrum, -a halter, from capere, to take hold of (the conjecture that it came from the Spanish cabra, goat, and estanto, standing, is untenable seems to have come into English (14th century) from French or Spanish shipmen at the time of the Crusades.
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CAT O' NINE TAILS [edit] Terminology The word is recorded in English since 1695, and it was probably so called in reference to its "claws" which inflict parallel wounds. There are equivalent terms in many languages, usually strictly translating, and also some analogous terms referring to a similar instrument's number of tails (cord or leather), such as the Dutch zevenstaart ('seven tail[s]'). [edit] Description The instrument traditionally has nine thongs as a result of the manner in which rope is braided. Thinner rope is made from three strands of yarn braided together, and thicker rope from three strands of thinner rope braided together. To make a cat o' nine tails, a rope is simply unraveled into three small ropes, and each of those next unraveled, again in three. A rationalisation (plausibly conceived post factum) for the number nine is that nine is thrice three[citation needed]: a Trinity of Trinities, fitting the concept of the wrongdoer going against the God of the Anglican or Catholic Church and hence against the Holy Trinity (the Father, the Son and the Holy Ghost) which, theocratically, thus puts the wrongdoer back on the path toward righteousness. It is also said that sailors had a holy cross tattooed on their backs to prevent it from 'unreligiously' being flogged, but there is no evidence for naval authorities awarding such exemption. In Trinidad and Tobago the "Cat" is made up of nine knotted thongs of cotton cord about 2½ feet or 76 cm long designed to lacerate the skin and cause intense pain. In the Bahamas it is made of rawhide. [edit] Variations Variations exist, either named cat (of x tails) or not, such as the whip used on adult Egyptian prisoners which had a cord on a cudgel branching into seven tails, each with six knots, used only on adult men, with boys being subject to caning, until Egypt banned the use of the device in 2001. Sometimes the term "cat" is used incorrectly to describe various other punitive flogging devices with multiple tails in any number, even one made from 80 twigs (so rather a limp birch) to flog a sick Iranian instead of 80 lashes normally applicable under shariah. [edit] Historical punishments [edit] Naval types and use The naval "cat", also known as the captain's daughter (since, in principle, it was only used under his authority), weighed about 13 ounces (370 g) and was composed of a baton (handle) and nine cords. Contrary to popular belief, the standard cat was not the most feared implement; being made of rope, it was rather less painful than a leather whip or a wooden birch-rod, while the modes of application (number and intensity of lashes, anatomical target, baring) of any implement can be more important than its intrinsic potential. [edit] Naval punishments All formal punishments — ordered by captain or court martial — were given ceremoniously on deck, the crew being summoned to ‘witness punishment’ (though usually adults and boys separated, which was apparently not strictly observed in practice) and drama enhanced by drum roll and a whole routine, including pauses, untangling of the tails, a drink of water and so on which is believed were more intended for the observing crew than for the actual participants. Informal 'daily' punishments, usually without assembly, including canings, were often left unrecorded. The thieves cat, to inflict punishment for theft, which was considered a particularly offensive crime on board ship, had each of its thongs knotted three times to cause additional pain. [edit] Napoleonic war period During the period of the Napoleonic wars, the naval cat's handle was made of rope about two feet (60 cm) long and about an inch (25 mm) in diameter, and was traditionally covered with red baize cloth. The "tails" were made of cord about a quarter inch (6 mm) in diameter and typically two feet long. A new cat was made for each flogging by a bosun's mate and kept in a red baize bag until use. In Trafalgar time, it was made by the condemned sailor during 24 hours in leg irons; the nine strongest falls were kept, and extra lashes were administered if any of the selected falls were found to be sub-standard. If several dozen lashes were awarded, each could be administered by a fresh bosun's mate — a left-handed one could be included to assure extra painful crisscrossing of the wounds. One dozen was usually awarded as a highly sensitizing 'prelude' to running the gauntlet. In some cases a cat with a wooden handle was used, and steel balls or barbs of wire were added to the tips of the thongs to maximize the potential flogging injury. [edit] Boys' punishment For summary punishment of Royal Navy boys, a lighter model was made, the reduced cat, also known as boy's cat, boy's pussy or just pussy, that had only five tails of smooth whip cord. If formally condemned by court martial, however, even boys would suffer the claw of the 'adult' cat. While adult sailors received their lashes on the back, they were administered to boys on the bare posterior, usually while "kissing the gunner's daughter" (bending over a gun barrel), just as boys' lighter 'daily' chastisement was usually over their (often naked) rear-end (mainly with a cane — this could be applied to the hand, but captains generally refused such impractical disablement — or a rope's end). Bare-bottom discipline was a tradition of the English upper and middle classes, who frequented public schools, so midshipmen (trainee officers, usually from ‘good families’, getting a cheaper equivalent education by enlisting) were not spared, at best sometimes allowed to receive their lashes inside a cabin. Still, it is reported that the ‘infantile’ humiliation of bare stern punishment was believed essential for optimal deterrence; cocky miscreants might brave the pain of the adult cat in the macho spirit of ‘taking it like a man’ or even as a ‘badge of honor’. On board training ships, where most of the crew were boys, the cat was never introduced, but their bare bottoms risked, as in other naval establishments on land, the sting of the birch, another favorite in public schools. [edit] British Army The British Army had a similar whip, though much lighter in construction; made of a drumstick with attached strings. The flogger was usually a drummer rather than a strong bosun's mate. Flogging with the cat o' nine tails fell into disuse around 1870. Naturally it was also used elsewhere in the Commonwealth, such as Canada (a dominion in 1867) until 1881. This 1812 drawing shows a drummer apparently lashing the buttocks of a naked soldier who is tied with spread legs on an A-frame made from sergeant's half pikes. In many places, soldiers were generally flogged stripped to the waist. [edit] Prison usage The cat-o'-nine-tails was also notoriously used on adult convicts in prisons; a 1951 memorandum ([1] on CorPun — possibly confirming earlier practice) ordered all UK male prisons to use only cats o' nine tails (and birches) from a national stock at Wandsworth prison, where they were to be 'thoroughly' tested before being supplied in triplicate to a prison whenever a procedure was pending for use as prison discipline. [edit] Penal colonies in Australia Especially harsh floggings were given with it in secondary penal colonies of early colonial Australia, particularly at such places as Norfolk Island (apparently this has 9 leather thongs each with a lead weight, meant as the ultimate deterrent for hardened life-convicts), Port Arthur and Moreton Bay (now Brisbane). [edit] Modern uses and types The use of judicial whippings was banned in Great Britain in 1948. The Cat was still being used in Australia in 1957 and the cat is still in punitive use in several post-colonial societies, including several Commonwealth countries, while no less severe judicial caning is practiced in South East Asia. Judicial corporal punishment has been abolished or declared unconstitutional since 1997 in Jamaica, St. Vincent and the Grenadines, South Africa, Zambia, Uganda (in 2001) and Fiji (in 2002; but a caning was given to four rapists in 1998). However, former colonies in the Caribbean have recently begun to reinstate flogging of the bare back. Antigua and Barbuda reinstated flogging in 1990, followed by the Bahamas in 1991 but subsequently banned by laws according to Bahamas Government website Bahamas Penal Codeand Barbados in 1993 (only to be formally declared inhumane and consequently unconstitutional by the Barbados Supreme Court). Jamaica in 1994 (flogging was banned again by the Jamaican Court of Appeal in 1998 [2]). Trinidad & Tobago never banned the "Cat" and birching. The use of both are regulated under the "Corporal Punishment (Offenders over Sixteen) Act" of 1953. Under this Act, use of the "Cat" was limited to male offenders over the age of 16. The age limit—repeatedly disregarded—was raised in 2000 to 18. Trinidad outlawed the corporal punishment of minors (both by courts and in schools) in 2001. The Government of Trinidad & Tobago has been accused of torture and "cruel, inhuman and degrading" treatment of prisoners, and on 11 March, 2005 was ordered by the Inter-American Court of Human Rights to pay US $50,000 for "moral damages" to a prisoner who had received 15 strokes of the "Cat" plus expenses for his medical and psychological care; it is unclear whether the Court's decisions were met. The Inter-American court has no jurisdiction in Trinidad and Tobago, whose highest court is the Privy Council in London. In most modern societies, the cat is a horror icon from the past, now often associated with BDSM culture, which implies another stigma according to some [citation needed]. In recent years the term cat o' nine tails is used imprecisely to describe almost any kind of multi-tailed whip, particularly those found in modern BDSM. These whips are usually made of soft leather, which reduces the potential for injury, and used in a way so as to not inflict terrible pain and, especially, wounds in a way that the voluntary participants find acceptable. Miniature versions are also known as ball whip because it is used for male genitorture. [edit] References in culture [edit] Expressions The still-popular sailor's song What do you do with a Drunken Sailor? has a verse that goes "Give him a taste of the captain's daughter" or "Throw him in bed with the captain's daughter". While this doesn't sound like a dire fate for the tipsy seaman, the term "captain's daughter" referred in naval jargon to the cat o' nine tails or a similar whip. The expression "to kiss the gunner's daughter" equally referred to a boy bending over a field gun, usually tied down, the trousers lowered, exposing the buttocks for a sound public spanking (often with a cane or birch), while adult sailors got their back striped in upright position. The common phrase, "not enough room to swing a cat," is often claimed to refers to a cat o' nine tails, yet there are examples of usage predating the known use of the cat o' nine tails (i.e. before 1695) and the phrase more likely refers to the practice of putting a live cat in a leather bottle and setting it swinging as a target for marksmen. For example, Shakespeare, in Much Ado About Nothing, writes: "Hang me in a bottle like a cat, and shoot at me." This has been the subject of correspondence in The Times in January 2007.[3] The phrase "letting the cat out of the bag" in the sense of revealing a secret may derive from the cat o' nine tails being kept in a red baize bag and being taken out when punishment is to be inflicted. For a sailor being punished for the first time, the secret of what the 'cat' is was thereby revealed. There are other possible explanations for this particular phrase (see Pig in a poke).
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FLAGELLATION Disciplinary use and torture Prisoners at a whipping post in a Delaware prison, circa 1907.Flogging is an approximate synonym that was probably derived from flagellum in the British navy, where flogging was a common disciplinary measure that became associated with a seaman's manly disregard for pain. Aboard ships, knittles or the cat o' nine tails was used for severe punishment, while a rope's end or starter was used to administer the lightest discipline to sailors. Flagellation probably originated in the Near East but quickly spread throughout the ancient world. In Sparta, young men were flogged as a test of their masculinity. The Jews limited flagellation to forty strokes, and in practice delivered forty strokes minus one, so as to avoid any possibility of breaking this law due to a miscount. Additionally they would have a doctor monitor the punishment, who would stop it if it became too much for the person to safely bear. In the Roman Empire, flagellation was often used as a prelude to crucifixion, and in this context is sometimes referred to as scourging. Whips with small pieces of metal or bone at the tips were commonly used. Such a device could easily cause disfigurement and serious trauma, such as ripping pieces of flesh from the body or loss of an eye. In addition to causing severe pain, the victim would be made to approach a state of hypovolemic shock due to loss of blood. The Romans reserved this torture for non-citizens, as stated in the lex Porcia and lex Sempronia, dating from 195 and 123 BC. The poet Horace refers to the horribile flagellum (horrible whip) in his Satires, calling for the end of its use. Typically, the one to be punished was stripped naked and bound to a low pillar so that he could bend over it, or chained to an upright pillar as to be stretched out. Two lictors (some reports indicate scourgings with four or six lictors) alternated blows from the bare shoulders down the body to the soles of the feet. There was no limit to the number of blows inflicted— this was left to the lictors to decide, though they were normally not supposed to kill the victim. Nonetheless, Livy, Suetonius and Josephus report cases of flagellation where victims died while still bound to the post. Flagellation was referred to as "half death" by some authors and apparently, many died shortly thereafter. Cicero reports in In Verrem, "pro mortuo sublatus brevi postea mortuus" ("taken away for a dead man, shortly thereafter he was dead"). Often the victim was turned over to allow flagellation on the chest, though this proceeded with more caution, as the possibility of inflicting a fatal blow was much greater. While flagellation and other forms of corporal punishment are now forbidden in most Western countries, flagellation is still a common form of punishment around the world, particularly in Islamic countries. Medically supervised caning is also still used as a punishment for some categories of crime in Singapore and Malaysia [1]. [edit] Australian penal colonies While common in the British Army and British Royal Navy as a means of discipline, flagellation also featured prominently in the British penal colonies in early colonial Australia. Given that convicts in Australia were already "imprisoned", punishments for offenses committed in the colonies could not usually result in imprisonment and thus usually consisted of corporal punishment such as hard labour or flagellation. Unlike Roman times, British law explicitly forbade the combination of corporal and capital punishment; thus, a convict was either flogged or hanged but never both. Flagellation took place either with a single whip or more notoriously, with the cat o' nine tails. Typically, the offender's upper half was bared and he was suspended by the hands beneath a tripod of wooden beams (known as 'the triangle'), while either one or two floggers administered the prescribed number of strokes. During the flogging, a doctor or other medical worker was consulted at regular intervals as to the condition of the prisoner - if the offender had fainted from blood loss or suffered extreme skin and flesh loss from the back, the punishment was usually suspended until such time that the offender had sufficiently healed. Once healed, the remainder of the required strokes were administered. Punishment was usually limited to 20, 50 or 100 strokes at one flogging, though records exist of prisoners in Australian penal colonies such as Norfolk Island or Port Arthur receiving more than 3,000 strokes over a number of months or years. Due to its prevalence, flagellation featured prominently in the culture of early colonial Australia. It was often a mark of pride for a flogged former convict to "show his stripes" (expose his flagellation scars) as an "iron man", or to hide them at all costs if an emancipated convict was attempting to rebuild some semblance of a normal life in society. Children in the Australian colonies were often observed playing "flogging games" where a doll or another child would pretend to be "strung from the triangles" and whipped. (See also: History of Australia).
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Gulf Of Mexico From Wikipedia, the free encyclopedia • Learn more about citing Wikipedia •Jump to: navigation, search Gulf of Mexico in 3D perspective.The Gulf of Mexico is the ninth largest body of water in the world. It is an ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. The shape of its basin is roughly oval and approximately 810 nautical miles (1,500 km) wide and filled with sedimentary rocks and debris. It connects with the Atlantic Ocean through the Florida Straits between the U.S. and Cuba, and with the Caribbean Sea (with which it forms the American Mediterranean Sea) via the Yucatan Channel between Mexico and Cuba. Tidal ranges are extremely small due to the narrow connection with the ocean. The gulf basin is approximately 615,000 mi² (1.6 million km²). Almost half of the basin is shallow intertidal waters. At its deepest it is 14,383 ft (4,384 m) at the Sigsbee Deep, an irregular trough more than 300 nautical miles (550 km) long. It was probably formed approximately 300 million years ago as a result of the seafloor sinking.[1] There is evidence that the Chicxulub Crater was formed when a large meteorite hit the earth 65 million years ago which may have led to the Cretaceous–Tertiary extinction event
NAUTICAL TERMS GLOSSARY Click here for a glossary of nautical terms, compliments of wilkpedia.
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Ocean Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean or global ocean.[1][2] This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[3] The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria: these divisions are (in descending order of size) the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean (which is sometimes subsumed as the southern portions of the Pacific, Atlantic, and Indian Oceans), and the Arctic Ocean (which is sometimes considered a sea of the Atlantic). The Pacific and Atlantic may be further subdivided by the equator into northerly and southerly portions. Smaller regions of the oceans are called seas, gulfs, bays and other names. There are also some smaller bodies of saltwater that are totally landlocked and not interconnected with the World Ocean, such as the Caspian Sea, the Aral Sea, and the Great Salt Lake – though they may be referred to as 'seas', they are actually salt lakes. Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt that covers the Earth's mantle where there are no continents. From this perspective, there are three oceans today: the World Ocean, the Caspian and the Black Seas, the latter two of which were formed by the collision of Cimmeria with Laurasia. The Mediterranean Sea is very nearly a discrete ocean, being connected to the World Ocean through the Strait of Gibraltar, and indeed several times over the last few million years movement of the African continent has closed the strait off entirely. The Black Sea is connected to the Mediterranean through the Bosporus, but this is in effect a natural canal cut through continental rock some 7,000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar. Physical properties Further information: Sea water The area of the World Ocean is 361 million square kilometers (139 million sq mi),[4] its volume is approximately 1,300 million cubic kilometers (310 million cu mi)[5], and its average depth is 3,790 meters (12,430 ft).[4] Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep.[2] The vast expanses of deep ocean (anything below 200m) cover about 64% of the Earth's surface.[6] This does not include seas not connected to the World Ocean, such as the Caspian Sea. The total mass of the hydrosphere is about 1.4 × 1021 kilograms, which is about 0.023% of the Earth's total mass. Less than 2% is freshwater, the rest is saltwater, mostly in the ocean. Color Main article: Color of water A common misconception is that the oceans are blue primarily because the sky is blue. In fact, water has a very slight blue color that can only be seen in large volumes. While the sky's reflection does contribute to the blue appearance of the surface, it is not the primary cause.[7] The primary cause is the absorption by the water molecules' nuclei of red photons from the incoming light, the only known example of color in nature resulting from vibrational, rather than electronic, dynamics.[8] Exploration Main article: Ocean exploration Map of large underwater features. (1995, NOAA)Travel on the surface of the ocean through the use of boats dates back to prehistoric times, but only in modern times has extensive underwater travel become possible. The deepest point in the ocean is the Marianas Trench located in the Pacific Ocean near the Northern Mariana Islands. It has a maximum depth of 10,923 meters (35,838 ft) [9]. It was fully surveyed in 1951 by the British naval vessel, "Challenger II" which gave its name to the deepest part of the trench, the "Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench, manned by a crew of two men. Much of the bottom of the world's oceans are unexplored and unmapped. A global image of many underwater features larger than 10 kilometers (6 mi) was created in 1995 based on gravitational distortions of the nearby sea surface. Regions The major oceanic divisionsOceans are divided into numerous regions depending on the physical and biological conditions of these areas. The pelagic zone includes all open ocean regions, and can be subdivided into further regions categorised by depth and light abundance. The photic zone covers the oceans from surface level to 200 metres down. This is the region where the photosynthesis most commonly occurs and therefore contains the largest biodiversity in the ocean. Since plants can only survive with photosynthesis any life found lower than this must either rely on material floating down from above (see marine snow) or find another primary source; this often comes in the form of hydrothermal vents in what is known as the aphotic zone (all depths exceeding 200m). The pelagic part of the photic zone is known as the epipelagic. The pelagic part of the aphotic zone can be further divided into regions that succeed each other vertically. The mesopelagic is the uppermost region, with its lowermost boundary at a thermocline of 10°C, which, in the tropics generally lies between 700 and 1,000m. After that is the bathypelagic lying between 10°C and 4°C, or between 700 or 1,000m and 2,000 or 4,000m. Lying along the top of the abyssal plain is the abyssalpelagic, whose lower boundary lies at about 6,000m. The final zone falls into the oceanic trenches, and is known as the hadalpelagic. This lies between 6,000m and 10,000m and is the deepest oceanic zone. Along with pelagic aphotic zones there are also benthic aphotic zones, these correspond to the three deepest zones. The bathyal zone covers the continental slope and the rise down to about 4,000m. The abyssal zone covers the abyssal plains between 4,000 and 6,000m. Lastly, the hadal zone corresponds to the hadalpelagic zone which is found in the oceanic trenches. The pelagic zone can also be split into two subregions, the neritic zone and the oceanic zone. The neritic encompasses the water mass directly above the continental shelves, while the oceanic zone includes all the completely open water. In contrast, the littoral zone covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the intertidal zone because it is the area where tide level affects the conditions of the region. Climate One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where the system forms). Ocean currents greatly affect Earth's climate by transferring warm or cold air and precipitation to coastal regions, where they may be carried inland by winds. The Antarctic Circumpolar Current encircles that continent, influencing the area's climate and connecting currents in several oceans. Ecology Lifeforms native to oceans include (among others): Radiata Fish Cetacea such as whales, dolphins and porpoises, Cephalopods such as the octopus Crustaceans such as lobsters and shrimp Marine worms Plankton Krill Economy The oceans are essential to transportation: most of the world's goods are moved by ship between the world's seaports. Important ship canals include the Saint Lawrence Seaway, Panama Canal, and Suez Canal. They are also an important source of valuable foodstuffs for the fishing industry. Some of these are shrimp, fish, crabs and lobster. Ancient oceans Continental drift has reconfigured the Earth's oceans, joining and splitting ancient oceans to form the current oceans. Ancient oceans include: Bridge River Ocean, the ocean between the ancient Insular Islands and North America. Iapetus Ocean, the southern hemisphere ocean between Baltica and Avalonia. Panthalassa, the vast world ocean that surrounded the Pangaea supercontinent. Rheic Ocean Slide Mountain Ocean, the ocean between the ancient Intermontane Islands and North America. Tethys Ocean, the ocean between the ancient continents of Gondwana and Laurasia. Khanty Ocean, the ocean between Baltica and Siberia. Mirovia, the ocean that surrounded the Rodinia supercontinent. Paleo-Tethys Ocean, the ocean between Gondwana and the Hunic terranes. Proto-Tethys Ocean, Pan-African Ocean, the ocean that surrounded the Pannotia supercontinent. Superocean, the ocean that surrounds a global supercontinent. Ural Ocean, the ocean between Siberia and Baltica. Extraterrestrial oceans See also Extraterrestrial oceans Earth is the only known planet with liquid water on its surface and is certainly the only one in our own solar system. However, liquid water is thought to be present under the surface of the Galilean moons Europa, and, with less certainty, Callisto and Ganymede. Geysers have been found on Enceladus, though these may not involve bodies of liquid water. Other icy moons may have once had internal oceans that have now frozen, such as Triton. The planets Uranus and Neptune may also possess large oceans of liquid water under their thick atmospheres, though their internal structure is not well understood at this time. There is currently much debate over whether Mars once had an ocean of water in its northern hemisphere, and over what happened to it if it did; recent findings by the Mars Exploration Rover mission indicate it had some long-term standing water in at least one location, but its extent is not known. Astronomers believe that Venus had liquid water and perhaps oceans in its very early history. If they existed, all trace of them seems to have vanished in later resurfacing. Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than an "ocean". The Cassini-Huygens space mission initially discovered only what appeared to be dry lakebeds and empty river channels, suggesting that Titan had lost what surface liquids it might have had. A more recent fly-by of Titan made by Cassini has produced radar images that strongly suggest hydrocarbon lakes near the polar regions where it is colder. Titan is also thought likely to have a subterranean water ocean under the mix of ice and hydrocarbons that forms its outer crust. Beyond the solar system, Gliese 581 c is at the right distance from its sun for liquid water to exist on the planet's surface. Since it does not transit its sun, there is no way to know if there is any water there. HD 209458b may have water vapour in its atmosphere - this is currently being disputed. Gliese 436 b is believed to have 'hot ice'. Neither of these planets are cool enough for liquid water: but if water molecules exist there, they are likely to be found also on planets at a suitable temperature.[10] Mythology The original concept of "ocean" goes back to notions of Mesopotamian and Indo-European mythology, imagining the world to be encircled by a great river. Okeanos, "???????" in Greek, reflects the ancient Greek observation that a strong current flowed off Gibraltar and their subsequent assumption that it was a great river. (Compare also Samudra from Hindu mythology and Jörmungandr from Norse mythology). The world was imagined to be enclosed by a celestial ocean above the heavens, and an ocean of the underworld below (compare Ras?, Varuna). This is evidenced for example in the account of Noah's flood in Genesis 7:11, where all the fountains of the great deep [were] broken up, and the windows of heaven were opened (KJV), inundating the world with the waters of the celestial ocean (see also deluge (mythology)). See also Oceanography International Maritime Organization Mediterranean sea Marginal sea Sea Seven Seas Sea level Sea level rise Sea salt Sea state Water World Ocean Day Marine biology Pelagic zone Southern Ocean Underground Oceans
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POINTS OF SAIL Points of sail From Wikipedia, the free encyclopedia Jump to: navigation, search Points of sail is the term used to describe a sailing boat's course in relation to the wind direction. The points of sail. A. In Irons (into the wind) B. Close Hauled C. Beam Reach D. Broad Reach E. RunningFirst, there is a distinction between the port tack and the starboard tack. If the wind is coming from anywhere on the port side, the boat is on port tack. Likewise if the wind is coming from the starboard side, the boat is on starboard tack. Except when head to wind, a boat will be on either port or starboard tack while on any point of sail. For purposes of the racing rules and "rules of the road," the wind is assumed to be coming from the side opposite that which the boom is carried. Contents [hide] 1 Head To Wind 2 No-Go Zone 3 Close Hauled 4 Reaching 5 Close Reach 6 Beam Reach 7 Broad Reach 8 Running Downwind [edit] Head To Wind At this point of sail the boat is headed directly into the wind. A boat turns through this point of sail as it performs a tack. The boat is on neither port nor starboard tack. Since a boat cannot sail directly into the wind, if a boat comes head to wind, and loses steerage it is said to be "in irons," and may begin to travel slowly backwards. To recover, the jib (headsail) is backed to one side, and the tiller is moved to the same side. In a single sailed boat the "push, push, pull, pull" technique (i.e. "push" the boom towards the wind, "push" the tiller away, and then "pull" the boom and tiller back to their normal positions) can be used which sails the boat backwards and steers the stern towards the wind. This results in the bow being pushed away from the wind and out of the no-go zone. Sailboats are usually put head to wind when raising or lowering sails. In this case, auxiliary (motorized) sailboats will typically be under power (engine running). In the sport of yacht racing, the current rules do not recognize a state in which a boat is on neither port nor starboard tack. Boats which are lying head to wind are either considered to be on their old tack, or on their new tack but in the act of tacking, and therefore required to stay clear of other boats. [edit] No-Go Zone The boat is pointed too close to the wind for the sails to generate any power (unless they are backed, see above). The sails will be luffing ("flapping") in the breeze and making noise, like a flag. The size of the no-go zone will differ based on the performance characteristics of the particular sailboat. For example, racing sailboats can usually sail much closer to the wind (i.e., fewer degrees off the wind direction) than cruising yachts. This is known as "pointing higher." Pointing ability is very important for racing sailboats as the real goal in a race is almost always velocity made good (VMG). VMG is the speed at which the boat is approaching the destination (usually a buoy or mark) as opposed to the speed at which the boat is moving through the water (boat speed). These two speeds almost always vary because, during a race, a boat usually cannot sail directly to the next mark. VMG may also refer to the upwind vector of boat speed (this is often the VMG expressed on sailing instruments). If a sailboat is tacking and turning into the wind with sufficient speed to complete the tack, when the boat is facing into the wind, the tacking boat is "luffing" but, due to forward speed, is still turning under control. If the boat attempts to tack with a slow initial speed, or otherwise stops forward motion while heading into the wind, the sailboat is said to be "in irons." Since there is no speed (no water flow past the rudder) there is no normal control of the direction of the boat, and it tends to drift directly backwards. To recover from this situation, the jib or forward most sail, can be backed (tightened and pushed out) on the side that is the desired tack until the boat is at a sufficient angle to the wind for sailing, and/or the rudder can be turned to the side that is the desired tack (the tiller pointed in the desired direction that you wish to go) and held until the boat is at the correct angle to the wind and resumes forward motion. [edit] Close Hauled Close hauledA boat is sailing close hauled when its sails are trimmed in tightly and it is sailing as close to the wind as it can without entering the No-Go Zone. This point of sail lets the boat travel diagonally upwind. This is a precise point of sail. However, the exact angle relative to the wind direction varies from boat to boat. A boat is considered to be "pinching" if the helmsman tries to sail above an efficient close-hauled course and the sails begin to luff slightly. [edit] Reaching ReachingWhen the boat is traveling approximately perpendicular to the wind, this is called reaching. A 'close' reach is somewhat toward the wind, and 'broad' reach is a little bit away from the wind (a 'beam' reach is with the wind precisely at a right angle to the boat). For most modern sailboats, reaching is the fastest way to travel. Different boats have different performance characteristics -- on some boats, the beam reach is the fastest point of sail; on others, a broad reach is faster. [edit] Close Reach This is any upwind angle between Close Hauled and a Beam Reach. "Fetch" (or "fetching") is a synonym in many English-speaking countries for a close reach. [edit] Beam Reach This is a course steered at right angles to the wind. This is a precise point of sail. Sails are put out at roughly 45 degrees. [edit] Broad Reach The wind is coming from behind the boat at an angle. This represents a range of wind angles between Beam Reach and Running Downwind. The sails are eased out away from the boat, but not as much as on a run or dead run (downwind run). [edit] Running Downwind Running goosewingedOn this point of sail, the wind is coming from directly behind the boat. Because running is the most difficult point of sail for modern yachts, and can be dangerous to those on board in the event of an accidental jibe, it is often called the "don't go zone". Modern racing yacht design favors sailing rigs that can point very high to windward, which means a high aspect ratio sail. Downwind performance suffers, but that is overcome by the use of a low aspect ratio spinnaker for running. When running, the mainsail is eased out as far as it will go. The jib will collapse because the mainsail blocks its wind, and must either be lowered and replaced by a spinnaker or set instead on the windward side of the boat. Running with the jib to windward is known as gull wing, goose wing,butterflying or wing and wing. A genoa gull-wings well, especially if stabilized by a whisker pole, which is similar to, but lighter than a spinnaker pole. In 'non-extras' or 'no flying sails' class races where spinnakers are not permitted, poled-out genoas are often used when running downwind. Cruising yachtsmen, when running downwind, will often set either a poled-out genoa or a pole-less cruising 'chute (or gennaker). When running downwind for protracted periods, for example when ocean-crossing in steady trade winds, cruisers sometimes set twin poled-out jibs without a mainsail. All of these options are more stable and require less trimming effort than a spinnaker. Steering is difficult when running because there is often little or no pressure on the tiller to provide feedback to the helmsman, so the boat may easily go off course. This tendency to turn off course when running can be dangerous, as the boat is least stable and can jibe accidentally if the lee side of the sail catches the wind. A preventer can be used on yachts to avoid this. Another problem with running in modern high aspect rigs is the fact that having the sail set at right angles to the wind guarantees a stall, and the stalled out wing sheds 'bubbles' of turbulence. Combined with the sea- and steering-induced rolling of the boat, this can build up a rolling resonance and lead to a broach or a death roll. Square rigged ships, since the sails develop lift off the top edges of the sails, and so are not necessarily stalled even on a dead run, are far better at running, since the conditions that lead to broaching are not present. They still, however, are difficult to keep on course, and require constant attention at the helm; when sailing on a reaching course, the boat is in a stable state, and it is possible to tie off the wheel and still maintain a steady course. [show]v • d • eSailing Manoeuvres Broach | Capsize | Close Hauled | Death Roll | Gybe | Gybe (Chinese) | Heaving to | Heeling | Hiking | In Irons | Jibe | Planing | Reaching | Running | Reefing | Rounding up | Tack | Trapezing | Turtling | Wear ship [show]v • d • eSails, spars and rigging Sails Course · Driver · Extra · Genoa · Gennaker · Jib · Lateen · Mainsail · Moonsail · Royal · Skysail · Spanker · Spinnaker · Spritsail · Staysail · Studding · Topgallant · Topsail · Trysail Sail anatomy and materials Clew · Foot · Head · Leech · Luff · Roach · Tack · Dacron · Kevlar · Twaron Spars Boom · Bowsprit · Dolphin striker · Fore-mast · Gaff · Jackstaff · Jigger-mast · Jury rig · Main-mast · Mast · Mizzen-mast · Masthead truck · Spinnaker pole · Topmast · Yard Rigging components Backstay · Block · Boom vang · Braces · Buntlines · Cleat · Clevis pin · Clewlines · Cunningham · Downhaul · Forestay · Gasket · Gooseneck · Guy · Halyard · Outhaul · Parrel beads · Peak · Preventer · Ratlines · Running rigging · Shackle · Standing rigging · Sheet · Shroud · Stay mouse · Stays · Throat · Topping lift · Trapeze Retrieved from "http://en.wikipedia.org/wiki/Points_of_sail" Categories: Sailing manoeuvres | Sailboat anatomy ViewsArticle Discussion Edit this page History Personal toolsSign in / create account Navigation Main Page Contents Featured content Current events Random article interaction About Wikipedia Community portal Recent changes Contact Wikipedia Donate to Wikipedia Help Search Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages Italiano ????????? 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RADAR Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. A transmitter emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very weak, radio signals can easily be amplified. This enables a radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, measuring ocean surface waves, air traffic control, police detection of speeding traffic, and by the military. It was originally called RDF (Radio Direction Finder) in Britain. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. The term has since entered the English language as a standard word, radar, losing the capitalization in the process.
Contents [hide]
1 History 2 Principles 2.1 Reflection 2.2 Radar equation 2.3 Polarization 2.4 Interference 2.4.1 Noise 2.4.2 Clutter 2.4.3 Jamming 3 Radar signal processing 3.1 Distance measurement 3.1.1 Transit time 3.1.2 Frequency modulation 3.2 Speed measurement 3.3 Reduction of interference effects 3.4 Plot And Track Extraction 4 Radar engineering 4.1 Antenna design 4.1.1 Parabolic reflector 4.1.2 Types of scan 4.1.3 Slotted waveguide 4.1.4 Phased array 4.2 Frequency bands 4.3 Radar modulators 4.4 Radar coolant 5 Radar functions and roles 5.1 Detection and search radars 5.2 Threat radars 5.3 Missile guidance systems 5.4 Battlefield and reconnaissance radar 5.5 Air Traffic Control and navigation 5.6 Space and range instrumentation radar systems 5.7 Weather-sensing Radar systems 5.8 Radars for biological research 5.9 Through The Wall Radar Systems 6 See also 7 Notes 8 References 9 Further reading 10 External links [edit] History
Main article: History of radar
Several inventors, scientists, and engineers contributed to the development of radar. The first to use radio waves to detect "the presence of distant metallic objects via radio waves" was Christian Hülsmeyer, who in 1904 demonstrated the feasibility of detecting the presence of a ship in dense fog, but not its distance.[2][3] He received Reichspatent Nr. 165546[4] for his pre-radar device in April 1904, and later patent 169154[5] for a related amendment for ranging. He also received a patent [6] in England for his telemobiloscope on September 22, 1904.[2][7]
Nikola Tesla, in August 1917, first established principles regarding frequency and power level for the first primitive radar units.[8] He stated, "[...] by their [standing electromagnetic waves] use we may produce at will, from a sending station, an electrical effect in any particular region of the globe; [with which] we may determine the relative position or course of a moving object, such as a vessel at sea, the distance traversed by the same, or its speed."
Before the Second World War, developments by the Americans (Dr. Robert M. Page tested the first monopulse radar in 1934),[9] the Germans, the French (French Patent n° 788795 in 1934)[10][11] and mainly the British who were the first to fully exploit it as a defence against aircraft attack (British Patent GB593017 by Robert Watson-Watt in 1935)[11][12][13] led to the first real radars. Hungarian Zoltán Bay produced a working model by 1936 at the Tungsram laboratory in the same vein.
In 1934, Émile Girardeau, working with the first French radar systems, stated he was building radar systems "conceived according to the principles stated by Tesla". [1]
The war precipitated research to find better resolution, more portability and more features for the new defence technology. Post-war years have seen the use of radar in fields as diverse as air traffic control, weather monitoring, astrometry and road speed control.
[edit] Principles
[edit] Reflection
Brightness can indicate reflectivity as in this 1960 weather radar image. The radar's frequency, pulse form, and antenna largely determine what it can observe.Electromagnetic waves reflect (scatter) from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or a vacuum, or other significant change in atomic density between the object and what's surrounding it, will usually scatter radar (radio) waves. This is particularly true for electrically conductive materials, such as metal and carbon fiber, making radar particularly well suited to the detection of aircraft and ships. Radar absorbing material, containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection. This is the radio equivalent of painting something a dark color.
Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror. If the wavelength is much longer than the size of the target, the target is polarized (positive and negative charges are separated), like a dipole antenna. This is described by Rayleigh scattering, an effect that creates the Earth's blue sky and red sunsets. When the two length scales are comparable, there may be resonances. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas some modern systems use shorter wavelengths (a few centimetres or shorter) that can image objects as small as a loaf of bread.
Short radio waves reflect from curves and corners, in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the reflective surfaces. A structure consisting of three flat surfaces meeting at a single corner, like the corner on a box, will always reflect waves entering its opening directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation and to reduce collisions. For similar reasons, objects attempting to avoid detection will angle their surfaces in a way to eliminate inside corners and avoid surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft. These precautions do not completely eliminate reflection because of diffraction, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross section.
[edit] Radar equation
The amount of power Pr returning to the receiving antenna is given by the radar equation:
where
Pt = transmitter power Gt = gain of the transmitting antenna Ar = effective aperture (area) of the receiving antenna σ = radar cross section, or scattering coefficient, of the target F = pattern propagation factor Rt = distance from the transmitter to the target Rr = distance from the target to the receiver. In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range. This yields:
This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small.
The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects should also be considered.
Other mathematical developments in radar signal processing include time-frequency analysis (Weyl Heisenberg or wavelet), as well as the chirplet transform which makes use of the fact that radar returns from moving targets typically "chirp" (change their frequency as a function of time, as does the sound of a bird or bat).
[edit] Polarization
In the transmitted radar signal, the electric field is perpendicular to the direction of propagation, and this direction of the electric field is the polarization of the wave. Radars use horizontal, vertical, linear and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate a fractal surface, such as rocks or soil, and are used by navigation radars.
[edit] Interference
Radar systems must overcome several different sources of unwanted signals in order to focus only on the actual targets of interest. These unwanted signals may originate from internal and external sources, both passive and active. The ability of the radar system to overcome these unwanted signals defines its signal-to-noise ratio (SNR): the higher a system's SNR, the better it is in isolating actual targets from the surrounding noise signals.
[edit] Noise
Signal noise is an internal source of random variations in the signal, which is inherently generated to some degree by all electronic components. Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. The lower the power of the desired signal, the more difficult it is to discern it from the noise (similar to trying to hear a whisper while standing near a busy road). Therefore, the most important noise sources appear in the receiver and much effort is made to minimize these factors. Noise figure is a measure of the noise produced by a receiver compared to an ideal receiver, and this needs to be minimized.
Noise is also generated by external sources, most importantly the natural thermal radiation of the background scene surrounding the target of interest. In modern radar systems, due to the high performance of their receivers, the internal noise is typically about equal to or lower than the external scene noise. An exception is if the radar is aimed upwards at clear sky, where the scene is so cold that it generates very little thermal noise.
There will be also Flicker noise due to electrons transit, but depending on 1/f, will be much lower than thermal noise when the frequency is high. Hence, in pulse radar, the system will be always heterodyne. See intermediate frequency.
[edit] Clutter
Clutter refers to actual radio frequency (RF) echoes returned from targets which are by definition uninteresting to the radar operators in general. Such targets mostly include natural objects such as ground, sea, precipitation (such as rain, snow or hail), sand storms, animals (especially birds), atmospheric turbulence, and other atmospheric effects, such as ionosphere reflections and meteor trails. Clutter may also be returned from man-made objects such as buildings and, intentionally, by radar countermeasures such as chaff.
Some clutter may also be caused by a long radar waveguide between the radar transceiver and the antenna. In a typical plan position indicator (PPI) radar with a rotating antenna, this will usually be seen as a "sun" or "sunburst" in the centre of the display as the receiver responds to echoes from dust particles and misguided RF in the waveguide. Adjusting the timing between when the transmitter sends a pulse and when the receiver stage is enabled will generally reduce the sunburst without affecting the accuracy of the range, since most sunburst is caused by a diffused transmit pulse reflected before it leaves the antenna.
While some clutter sources may be undesirable for some radar applications (such as storm clouds for air-defence radars), they may be desirable for others (meteorological radars in this example). Clutter is considered a passive interference source, since it only appears in response to radar signals sent by the radar.
There are several methods of detecting and neutralizing clutter. Many of these methods rely on the fact that clutter tends to appear static between radar scans. Therefore, when comparing subsequent scans echoes, desirable targets will appear to move and all stationary echoes can be eliminated. Sea clutter can be reduced by using horizontal polarization, while rain is reduced with circular polarization (note that meteorological radars wish for the opposite effect, therefore using linear polarization the better to detect precipitation). Other methods attempt to increase the signal-to-clutter ratio.
CFAR (Constant False-Alarm Rate, a form of Automatic Gain Control, or AGC) is a method relying on the fact that clutter returns far outnumber echoes from targets of interest. The receiver's gain is automatically adjusted to maintain a constant level of overall visible clutter. While this does not help detect targets masked by stronger surrounding clutter, it does help to distinguish strong target sources. In the past, radar AGC was electronically controlled and affected the gain of the entire radar receiver. As radars evolved, AGC became computer-software controlled, and affected the gain with greater granularity, in specific detection cells.
Radar multipath echoes from an actual target cause ghosts to appear.Clutter may also originate from multipath echoes from valid targets due to ground reflection, atmospheric ducting or ionospheric reflection/refraction. This specific clutter type is especially bothersome, since it appears to move and behave like other normal (point) targets of interest, thereby creating a ghost. In a typical scenario, an aircraft echo is multipath-reflected from the ground below, appearing to the receiver as an identical target below the correct one. The radar may try to unify the targets, reporting the target at an incorrect height, or - worse - eliminating it on the basis of jitter or a physical impossibility. These problems can be overcome by incorporating a ground map of the radar's surroundings and eliminating all echoes which appear to originate below ground or above a certain height. In newer ATC radar equipment algorithms are used to identify the false targets by comparing the current pulse returns, to those adjacent, as well as calculating return improbabilities due to calculated height, distance, and radar timing.
[edit] Jamming
Radar jamming refers to RF signals originating from sources outside the radar, transmitting in the radar's frequency and thereby masking targets of interest. Jamming may be intentional, as with an electronic warfare (EW) tactic, or unintentional, as with friendly forces operating equipment that transmits using the same frequency range. Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals.
Jamming is problematic to radar since the jamming signal only needs to travel one-way (from the jammer to the radar receiver) whereas the radar echoes travel two-ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver. Jammers therefore can be much less powerful than their jammed radars and still effectively mask targets along the line of sight from the jammer to the radar (Mainlobe Jamming). Jammers have an added effect of affecting radars along other line-of-sights, due to the radar receiver's sidelobes (Sidelobe Jamming).
Mainlobe jamming can generally only be reduced by narrowing the mainlobe solid angle, and can never fully be eliminated when directly facing a jammer which uses the same frequency and polarization as the radar. Sidelobe jamming can be overcome by reducing receiving sidelobes in the radar antenna design and by using an omnidirectional antenna to detect and disregard non-mainlobe signals. Other anti-jamming techniques are frequency hopping and polarization. See Electronic counter-counter-measures for details.
Interference has recently become a problem for C-band (5.66 GHz) meteorological radars with the proliferation of 5.4 GHz band WiFi equipment.[14]
[edit] Radar signal processing
[edit] Distance measurement
[edit] Transit time
Pulse radar One way to measure the distance to an object is to transmit a short pulse of radio signal (electromagnetic radiation), and measure the time it takes for the reflection to return. The distance is one-half the product of round trip time (because the signal has to travel to the target and then back to the receiver) and the speed of the signal. Since radio waves travel at the speed of light (186,000 miles per second or 300,000,000 meters per second), accurate distance measurement requires high-performance electronics.
In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a device called a duplexer, the radar switches between transmitting and receiving at a predetermined rate. The minimum range is calculated by measuring the length of the pulse multiplied by the speed of light, divided by two. In order to detect closer targets one must use a shorter pulse length.
A similar effect imposes a maximum range as well. If the return from the target comes in when the next pulse is being sent out, once again the receiver cannot tell the difference. In order to maximize range, one wants to use longer times between pulses, or commonly referred to as a pulse repetition time (PRT).
These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. This could be offset by using more pulses, but this would shorten the maximum range again. So each radar uses a particular type of signal. Long-range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. This pattern of pulses and pauses is known as the pulse repetition frequency (or PRF), and is one of the main ways to characterize a radar. As electronics have improved many radars now can change their PRF thereby changing their range. The newest radars actually fire 2 pulses during one cell. One for short range (~6 miles) and a separate signal for longer ranges (~60 miles).
The distance resolution and the characteristics of the received signal as compared to noise depends heavily on the shape of the pulse. The pulse is often modulated to achieve better performance thanks to a technique known as pulse compression.
[edit] Frequency modulation
Another form of distance measuring radar is based on frequency modulation. Frequency comparison between two signals is considerably more accurate, even with older electronics, than timing the signal. By changing the frequency of the returned signal and comparing that with the original, the difference can be easily measured.
This technique can be used in continuous wave radar, and is often found in aircraft radar altimeters. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a sine wave or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared using a simple beat frequency modulator that produces an audio frequency tone from the returned signal and a portion of the transmitted signal.
Since the signal frequency is changing, by the time the signal returns to the aircraft the broadcast has shifted to some other frequency. The amount of that shift is greater over longer times, so greater frequency differences mean a longer distance, the exact amount being the "ramp speed" selected by the electronics. The amount of shift is therefore directly related to the distance traveled, and can be displayed on an instrument. This signal processing is similar to that used in speed detecting Doppler radar. Example systems using this approach are AZUSA, MISTRAM, and UDOP.
A further advantage is that the radar can operate effectively at relatively low frequencies, comparable to that used by UHF television. This was important in the early development of this type when high frequency signal generation was difficult or expensive.
[edit] Speed measurement
Speed is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a memory capacity to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making grease-pencil marks on the radar screen, and then calculating the speed using a slide rule. Modern radar systems perform the equivalent operation faster and more accurately using computers.
However, if the transmitter's output is coherent (phase synchronized), there is another effect that can be used to make almost instant speed measurements (no memory is required), known as the Doppler effect. Most modern radar systems use this principle in the pulse-doppler radar system. Return signals from targets are shifted away from this base frequency via the Doppler effect enabling the calculation of the speed of the object relative to the radar. The Doppler effect is only able to determine the relative speed of the target along the line of sight from the radar to the target. Any component of target velocity perpendicular to the line of sight cannot be determined by using the Doppler effect alone, but it can be determined by tracking the target's azimuth over time. Additional information of the nature of the Doppler returns may be found in the radar signal characteristics article.
It is also possible to make a radar without any pulsing, known as a continuous-wave radar (CW radar), by sending out a very pure signal of a known frequency. CW radar is ideal for determining the radial component of a target's velocity, but it cannot determine the target's range. CW radar is typically used by traffic enforcement to measure vehicle speed quickly and accurately where range is not important.
[edit] Reduction of interference effects
Signal processing is employed in radar systems to reduce the interference effects. Signal processing techniques include moving target indication (MTI), pulse doppler, moving target detection (MTD) processors, correlation with secondary surveillance radar (SSR) targets and space-time adaptive processing (STAP). Constant false alarm rate (CFAR) and digital terrain model (DTM) processing are also used in clutter environments.
[edit] Plot And Track Extraction
Radar video returns on aircraft can be subjected to a plot extraction process whereby spurious and interfering signals are discarded. A sequence of target returns can be monitored through a device known as a plot extractor. The non relevant real time returns can be removed from the displayed information and a single plot displayed. A sequence of plots can then be monitored and a 'track' formed, thus easing the identification of a genuine aircraft target through unwanted and non relevant radar returns.
[edit] Radar engineering
Radar componentsA radar has different components:
A transmitter that generates the radio signal with an oscillator such as a klystron or a magnetron and controls its duration by a modulator. A waveguide that links the transmitter and the antenna. A duplexer that serves as a switch between the antenna and the transmitter or the receiver for the signal when the antenna is used in both situations. A receiver. Knowing the shape of the desired received signal (a pulse), an optimal receiver can be designed using a matched filter. An electronic section that controls all those devices and the antenna to perform the radar scan ordered by a software. A link to end users. [edit] Antenna design
Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located.
Early systems tended to use omni-directional broadcast antennas, with directional receiver antennas which were pointed in various directions. For instance the first system to be deployed, Chain Home, used two straight antennas at right angles for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by rotating the antenna so one display showed a maximum while the other shows a minimum.
One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is a small part of that transmitted. To get a reasonable amount of power on the "target", the transmitting aerial should also be directional.
[edit] Parabolic reflector
More modern systems use a steerable parabolic "dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combine two radar frequencies in the same antenna in order to allow automatic steering, or radar lock.
[edit] Types of scan
Primary Scan: A scanning technique where the main antenna aerial is moved to produce a scanning beam, examples include circular scan, sector scan etc Secondary Scan: A scanning technique where the antenna feed is moved to produce a scanning beam, example include conical scan, unidirectional sector scan, lobe switching etc. Palmer Scan: A scanning technique that produces a scanning beam by moving the main antenna and its feed. A Palmer Scan is a combination of a Primary Scan and a Secondary Scan. Phased array: Not all radar antennas must rotate to scan the sky.
[edit] Slotted waveguide
Main article: Slotted waveguide
Applied similarly to the parabolic reflector the slotted waveguide is moved mechanically to scan and is particularly suitable for non-tracking surface scan systems, where the vertical pattern may remain constant. Owing to lower cost and less wind exposure, shipboard, airport surface, and harbour surveillance radars now use this in preference to the parabolic antenna.
[edit] Phased array
Main article: Phased array
Another method of steering is used in a phased array radar. This uses an array of similar aerials suitably spaced, the phase of the signal to each individual aerial being controlled so that the signal is reinforced in the desired direction and cancels in other directions. If the individual aerials are in one plane and the signal is fed to each aerial in phase with all others then the signal will reinforce in a direction perpendicular to that plane. By altering the relative phase of the signal fed to each aerial the direction of the beam can be moved because the direction of constructive interference will move. Because phased array radars require no physical movement the beam can scan at thousands of degrees per second, fast enough to irradiate and track many individual targets, and still run a wide-ranging search periodically. By simply turning some of the antennas on or off, the beam can be spread for searching, narrowed for tracking, or even split into two or more virtual radars. However, the beam cannot be effectively steered at small angles to the plane of the array, so for full coverage multiple arrays are required, typically disposed on the faces of a triangular pyramid (see picture).
Phased array radars have been in use since the earliest years of radar use in World War II, but limitations of the electronics led to fairly poor accuracy. Phased array radars were originally used for missile defense. They are the heart of the ship-borne Aegis combat system, and the Patriot Missile System, and are increasingly used in other areas because the lack of moving parts makes them more reliable, and sometimes permits a much larger effective antenna, useful in fighter aircraft applications that offer only confined space for mechanical scanning.
As the price of electronics has fallen, phased array radars have become more and more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is far offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are still widely used in roles where cost is a significant factor such as air traffic surveillance, weather radars and similar systems.
Phased array radars are also valued for use in aircraft, since they can track multiple targets. The first aircraft to use a phased array radar is the B-1B Lancer. The first aircraft fighter to use phased array radar was the Mikoyan MiG-31. The MiG-31M's SBI-16 Zaslon phased array radar is considered to be the world's most powerful fighter radar [2]. Phased-array interferometry "aperture synthesis" techniques, using an array of separate dishes that are phased into a single effective aperture, are not typically used for radar applications, although they are widely used in radio astronomy. Because of the Thinned array curse, such arrays of multiple apertures, when used in transmitters, result in narrow beams at the expense of reducing the total power transmitted to the target. In principle, such techniques used could increase the spatial resolution, but the lower power means that this is generally not effective. Aperture synthesis by post-processing of motion data from a single moving source, on the other hand, is widely used in space and airborne radar systems (see "Synthetic aperture radar").
[edit] Frequency bands
The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world in the 21st century. They have been adopted in the United States by the IEEE, and internationally by the ITU. Most countries have additional regulations to control which parts of each band are available for civilian or military use.
Other users of the radio spectrum, such as the broadcasting and electronic countermeasures (ECM) industries, have replaced the traditional military designations with their own systems.
Radar frequency bands Band Name Frequency Range Wavelength Range Notes HF 3–30 MHz 10–100 m coastal radar systems, over-the-horizon radar (OTH) radars; 'high frequency' P < 300 MHz 1 m+ 'P' for 'previous', applied retrospectively to early radar systems VHF 50–330 MHz 0.9–6 m very long range, ground penetrating; 'very high frequency' UHF 300–1000 MHz 0.3–1 m very long range (e.g. ballistic missile early warning), ground penetrating, foliage penetrating; 'ultra high frequency' L 1–2 GHz 15–30 cm long range air traffic control and surveillance; 'L' for 'long' S 2–4 GHz 7.5–15 cm terminal air traffic control, long-range weather, marine radar; 'S' for 'short' C 4–8 GHz 3.75–7.5 cm Satellite transponders; a compromise (hence 'C') between X and S bands; weather X 8–12 GHz 2.5–3.75 cm missile guidance, marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ±25 MHz is used for airport radar. Named X band because the frequency was a secret during WW2. Ku 12–18 GHz 1.67–2.5 cm high-resolution mapping, satellite altimetry; frequency just under K band (hence 'u') K 18–27 GHz 1.11–1.67 cm from German kurz, meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz. Ka 27–40 GHz 0.75–1.11 cm mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz. mm 40–300 GHz 7.5 mm – 1 mm millimetre band, subdivided as below. The letter designators appear to be random, and the frequency ranges dependent on waveguide size. Multiple letters are assigned to these bands by different groups. These are from Baytron, a now defunct company that made test equipment. Q 40–60 GHz 7.5 mm – 5 mm Used for Military communication. V 50–75 GHz 6.0–4 mm Very strongly absorbed by the atmosphere. E 60–90 GHz 6.0–3.33 mm W 75–110 GHz 2.7 – 4.0 mm used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging. [edit] Radar modulators
Modulators are sometimes called pulsers and act to provide the short pulses of power to the magnetron. This technology is known as Pulsed power. In this way, the transmitted pulse of RF radiation is kept to a defined, and usually very short, duration. Modulators consist of a high voltage pulse generator formed from a HV supply, a pulse forming network or line (PFN) and a high voltage switch such as a thyratron.
A klystron tube is an amplifier, so it can be modulated by its low power input signal.
[edit] Radar coolant
Coolanol and PAO (poly-alpha olefin) are the two main coolants used to cool airborne radar equipment today.[citation needed]
The U.S. Navy has instituted a program named Pollution Prevention (P2) to reduce or eliminate the volume and toxicity of waste, air emissions, and effluent discharges. Because of this Coolanol is used less often today.
PAO is a synthetic lubricant composition is a blend of a polyol ester admixed with effective amounts of an antioxidant, yellow metal pacifier and rust inhibitors. The polyol ester blend includes a major proportion of poly(neopentyl polyol) ester blend formed by reacting poly(pentaerythritol) partial esters with at least one C7 to C12 carboxylic acid mixed with an ester formed by reacting a polyol having at least two hydroxyl groups and at least one C8-C10 carboxylic acid. Preferably, the acids are linear and avoid those which can cause odours during use. Effective additives include secondary arylamine antioxidants, triazole derivative yellow metal pacifier and an amino acid derivative and substituted primary and secondary amine and/or diamine rust inhibitor.
A synthetic coolant/lubricant composition, comprising an ester mixture of 50 to 80 weight percent of poly(neopentyl polyol) ester formed by reacting a poly(neopentyl polyol) partial ester and at least one linear monocarboxylic acid having from 6 to 12 carbon atoms, and 20 to 50 weight percent of a polyol ester formed by reacting a polyol having 5 to 8 carbon atoms and at least two hydroxyl groups with at least one linear monocarboxylic acid having from 7 to 12 carbon atoms, the weight percents based on the total weight of the composition.
[edit] Radar functions and roles
Surface search radar display commonly found on ships
[edit] Detection and search radars
Early Warning (EW) Radar Systems Early Warning Radar Ground Control Intercept (GCI) Radar Airborne Early Warning (AEW) Over-the-Horizon (OTH) Radar Target Acquisition (TA) Radar Systems Surface-to-Air Missile (SAM) Systems Anti-Aircraft Artillery (AAA) Systems Surface Search (SS) Radar Systems Surface Search Radar Coastal Surveillance Radar Harbour Surveillance Radar Antisubmarine Warfare (ASW) Radar Height Finder (HF) Radar Systems Gap Filler Radar Systems [edit] Threat radars
Target Tracking (TT) Systems AAA Systems SAM Systems Precision Approach Radar (PAR) Systems Multi-Function Systems Fire Control (FC) Systems Acquisition Mode Semiautomatic Tracking Mode Manual Tracking Mode Airborne Intercept (AI) Radars Search Mode TA Mode TT Mode Target Illumination (TI) Mode Missile Guidance (MG) Mode [edit] Missile guidance systems
Air-to-Air Missile (AAM) Air-to-Surface Missile (ASM) SAM Systems Surface-to-Surface Missiles (SSM) Systems [edit] Battlefield and reconnaissance radar
Military map marking symbol Radar as of NATO standard APP-6aBattlefield Surveillance Systems Battlefield Surveillance Radars Countermortar/Counterbattery Systems Shell Tracking Radars Air Mapping Systems Side Looking Airborne Radar (SLAR) Synthetic Aperture Radar (SAR) Perimeter Surveillance Radar (PSR) [edit] Air Traffic Control and navigation
Air traffic control radar at London Heathrow AirportAir Traffic Control Systems Air Traffic Control (ATC) Radars Secondary Surveillance Radar (SSR) (Airport Surveillance Radar) Ground Control Approach (GCA) Radars Precision Approach Radar (PAR) Systems Distance Measuring Equipment (DME) Radio Beacons Radar Altimeter (RA) Systems Terrain-Following Radar (TFR) Systems [edit] Space and range instrumentation radar systems
Space (SP) Tracking Systems Range Instrumentation (RI) Systems Video Relay/Downlink Systems Space-Based Radar [edit] Weather-sensing Radar systems
Weather radar Wind profilers Storm front reflectivities on a Weather radar screen (NOAA)
Wind profiling radar
[edit] Radars for biological research
Bird radar Insect radar Surveillance radar (mostly X and S band, i.e. primary ATC Radars) Tracking radar (mostly X band, i.e. Fire Control Systems) [edit] Through The Wall Radar Systems
Radar systems which operate using Ultra Wideband technology can sense a human behind walls. This is possible since the reflective characteristics of humans are generally greater than those of the typical materials used in construction. However, since humans reflect far less radar energy than metal does, these systems require sophisticated technology to isolate human targets and moreover to process any sort of detailed image.
[edit] See also
Electronics Portal Nautical Portal Crossed-field amplifier Definitions Amplitude monopulse Bistatic Doppler Bistatic range Constant false alarm rate Gallium arsenide Klystron tube List of radars Cavity magnetron Over-the-horizon radar Radio Radar History Secrets of Radar Museum Similar detection and ranging methods LIDAR LORAN Sonar Traveling wave tube (TWT) Types and uses of radar 3D radar Active Electronically Scanned Array (AESA) Bistatic radar Continuous-wave radar Doppler radar Fm-cw radar Imaging radar Incoherent scatter Low probability of intercept Millimetre cloud radar Monopulse radar Passive radar Planar array radar Precision Approach Radar Pulse-doppler Radar gun, for traffic policing and as used in some sports SCR-270 radar X-band radar H2S radar Chain Home Man portable radar [edit] Notes
^ Ronald Reagan Test Site on the Kwajalein atoll ^ a b Christian Hülsmeyer by Radar World ^ (German) Christian Hülsmeyer Biografie ^ DE patent 165546 Verfahren, um metallische Gegenstände mittels elektrischer Wellen einem Beobachter zu melden. ^ DE patent 169154 Verfahren zur Bestimmung der Entfernung von metallischen Gegenständen (Schiffen o. dgl.), deren Gegenwart durch das Verfahren nach Patent 16556 festgestellt wird. ^ GB patent 13170 Telemobiloscope ^ (German) 100. Jahre Radar Improvement in Hertzian-wave Projecting and Receiving Apparatus for Locating the Position of Distant Metal Objects in 100 years of radar a German publication ^ The Electrical Experimenter, 1917 ^ Goebel, Greg (2007-01-01). The Wizard War: WW2 & The Origins Of Radar, Chapter 1: The British Invention of Radar. Retrieved on 2007-03-24. ^ FR patent 788795 Nouveau système de repérage d'obstacles et ses applications ^ a b (French) Copy of Patents for the invention of radar on www.radar-france.fr ^ British man first to patent radar official site of the Patent Office ^ GB patent 593017 Improvements in or relating to wireless systems ^ Example of WiFi equipment jamming meteorological radars. [edit] References
Barrett, Dick, "All you ever wanted to know about British air defence radar". The Radar Pages. (History and details of various British radar systems) Buderi, "Telephone History: Radar History". Privateline.com. (Anecdotal account of the carriage of the world's first high power cavity magnetron from Britain to the US during WW2.) Ekco Radar WW2 Shadow Factory The secret development of British Radar. ES310 "Introduction to Naval Weapons Engineering.". (Radar fundamentals section) Hollmann, Martin, "Radar Family Tree". Radar World. Penley, Bill, and Jonathan Penley, "Early Radar History - an Introduction". 2002. [edit] Further reading
Buderi, Robert, The invention that changed the world: the story of radar from war to peace, Simon & Schuster, 1996. ISBN 0-349-11068-9 ISBN 0-316-90715-4 Hall, P.S., T.K. Garland-Collins, R.S. Picton and R.G. Lee, Radar, Brassey's (UK) Ltd., 1991, Land Warfare Series: Vol 9, ISBN 0-08-037711-4. Kaiser, Gerald, Chapter 10 in "A Friendly Guide to Wavelets", Birkhauser, Boston, 1994. Jones, R.V., Most Secret War, ISBN 1-85326-699-X. R.V. Jones' account of his part in British Scientific Intelligence between 1939 and 1945, working to anticipate the German's radar, radio navigation and V1/V2 developments. Le Chevalier, François, Principles of Radar and Sonar Signal Processing, Artech House, Boston, London, 2002. ISBN 1-58053-338-8. Skolnik, Merrill I., Introduction to Radar Systems, McGraw-Hill (1st ed., 1962; 2nd ed., 1980; 3rd ed., 2001), ISBN 0-07-066572-9. The de-facto radar introduction bible. Skolnik, Merrill I., Radar Handbook. ISBN 0-07-057913-X widely used in the US since the 1970s. Stimson, George W., Introduction to Airborne Radar, SciTech Publishing (2nd edition, 1998), ISBN 1-891121-01-4. Written for the non-specialist. The first half of the book on radar fundamentals is also applicable to ground- and sea-based radar. Bragg, Michael., RDF1 The Location of Aircraft by Radio Methods 1935–1945, Hawkhead Publishing, Paisley 1988 ISBN 0-9531544-0-8 The history of ground radar in the UK during World War II Latham, Colin & Stobbs, Anne., Radar A Wartime Miracle, Sutton Publishing Ltd, Stroud 1996 ISBN 0-7509-1643-5 A history of radar in the UK during World War II told by the men and women who worked on it. Pritchard, David., The Radar War Germany's Pioneering Achievement 1904–1945 Patrick Stephens Ltd, Wellingborough 1989., ISBN 1-85260-246-5 Zimmerman, David., Britain's Shield Radar and the Defeat of the Luftwaffe, Sutton Publishing Ltd, Stroud, 2001., ISBN 0-7509-1799-7 Brown, Louis., A Radar History of World War II, Institute of Physics Publishing, Bristol, 1999., ISBN 0-7503-0659-9 Bowen, E.G., Radar Days, Institute of Physics Publishing, Bristol, 1987., ISBN 0-7503-0586-X Howse, Derek, Radar At Sea The Royal Navy in World War 2, Naval Institute Press, Annapolis, Maryland, USA, 1993, ISBN 1-55750-704-X [edit] External links
Wikimedia Commons has media related to: RadarChristian Hülsmeyer and about the early days of radar inventions Radar technology principles The first operational radar in France 1934 Historic Radar Archive Radar and RF related eBooks History of Radar Radar Invisibility with Metamaterials Radar Research Center-Italy Early radar development in the UK Principles of radar target acquisition and weapon guidance systems Cloaking and radar invisibility The Secrets of Radar Museum 84th Radar Evaluation Squadron Retrieved from "http://en.wikipedia.org/wiki/Radar"
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RATLINES Ratlines, pronounced "rattlin's", are lengths of thin line tied between the shrouds of a sailing ship to form a ladder. They are found invariably on square rigged ships whose crews must go aloft to stow the square sails, but may also be present on larger fore-and-aft rigged vessels in order to make repairs or conduct a lookout from a higher position. Sometimes, especially on the lower shrouds, they are made of wood rather than rope, in which case they are occasionally known as "ratbars" instead. Wooden ratlines can have holes bored through them to guide and organise lines between the deck and the rig; these would usually be clewlines and buntlines that are not under much load.
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REEFING Reefing is a sailing manoeuvre intended to reduce the area of a sail on a sailboat or sailing ship, which can improve the ship's stability and reduce the risk of capsizing, broaching, or damaging sails or boat hardware in a strong wind. Modern sailboats often combine reefing and furling of sails, as shown in fully furled Genoa headsail of the Bavaria 36 in the image at right. There are three common methods of reefing: conventional, roller, and jiffy. The latter two make sail-handling easier and allow reefing to be done with fewer crew members. [edit] Conventional reefing Diagram showing the names of the parts of a Bermudian-style mainsail, with reefing lines illustrated.Sails may have built-in alternate attachement points that allow their area to be reduced. In a mainsail, one to four horizontal rows of cringles, called reef points, may be placed above the foot of the sail. Tying the sail to the boom at these reef points forms a new tack and clew and reduces the sail's area. More than one row of reef points increases options for possible sail area. To perform the reef, crew must pull the reefing line as another crew is lowering the sail. Reefing is used mostly when the winds are too strong and are overpowering the boat and the steering. [edit] Roller reefing Roller reefing involves rolling or wrapping the sail around a wire, foil, or spar to reduce the sail's exposure to the wind. The mainsail is wrapped around the boom, which contains a mechanism in the gooseneck that rolls in the sail--or special hardware inside the boom or mast is used to reef the sail by winding it around a rotating foil. These latter systems are known as mainsail furling systems. Conventional roller reefing on a rotating boom can be difficult and time-consuming, typically requiring a crew member to work at the mast in heavy weather. By comparison, furling systems operate easily through control lines led to the cockpit. Roller reefing allows a more gradual and controllable method of reefing than conventional or jiffy reefing. [edit] Jiffy reefing Jiffy reefing, also called slab reefing or single line reefing, is quicker and easier than conventional reefing or conventional roller reefing and involves folding the sail in sections, or slabs, along the boom. One or two reefing lines placed through the reef cringles at the sail's luff and leach edges are used to pull those points down tight to the boom, creating a new tack and clew for the sail. Reefing lines can be led back to the cockpit, and crew members can perform reefing without going on deck in heavy weather. In jiffy reefing there is no need to tie to the boom at the reef cringles on the sail. The equipment for jiffy reefing is often integrated with Dutchman flaking, a furling technology that flakes (or folds up) the sail on alternate sides of the boom rather than on a messy pile on one side of the boom. [hide]v • d • eSailing Manoeuvres Broach | Capsize | Close Hauled | Death Roll | Gybe | Gybe (Chinese) | Heaving to | Heeling | Hiking | In Irons | Jibe | Planing | Reaching | Running | Reefing | Rounding up | Tack | Trapezing | Turtling | Wear ship Retrieved from "http://en.wikipedia.org/wiki/Reefing"
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REEFS In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water yet shallow enough to be a hazard to ships. Many reefs result from abiotic processes—deposition of sand, wave erosion planning down rock outcrops, and other natural processes—but the best-known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and calcareous algae. Reefs can be created artificially either by special construction or through deliberately sinking ships, but one can argue that these "reefs" are not real ones, as it is seldom the case that an artificial obstruction would be created that is a hazard to shipping. These structures are usually created to enhance physical complexity on generally featureless sand bottoms in order to attract a diverse assemblage of organisms, especially fish. Thus, "artificial reef" is a misnomer, though firmly established as the term used for man-made underwater habitat structures. Contents [hide] 1 Biotic reef types 2 Geologic reef definition 3 Geologic reef structures 4 External links [edit] Biotic reef types There are a number of biotic reef types, including oyster reefs, but the most massive and widely distributed are tropical coral reefs. Although corals are major contributors to the framework and bulk material comprising a coral reef, the organisms most responsible for reef growth against the constant assault from ocean waves are calcarous algae, especially, although not entirely, species of coralline algae. [edit] Geologic reef definition Geologists define reefs and related terms (for example, bioherm, biostrome, carbonate mound) using the factors of depositional relief, internal structure, and biotic composition. There is no consensus on one universally applicable definition. A useful definition distinguishes reefs from mounds as follows. Both are considered to be varieties of organosedimentary buildups: sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework. Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake of Utah (USA), and in Shark Bay, Western Australia. Cyanobacteria do not have skeletons and individuals are microscopic. Cyanobacteria encourage the precipitation or accumulation of calcium carbonate and can produce compositionally distinct sediment bodies that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today (stromatolites are microbial mounds with a laminated internal structure). Bryozoans and crinoids, common contributors to marine sediments during the Mississippian (for example), produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate. However, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief. [edit] Geologic reef structures Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits. Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician period. However, other organism groups, such as calcifying algae, especially members of the red algae Rhodophyta, and mollusks (especially the rudist bivalves during the Cretaceous period) have created massive structures at various times. During the Cambrian period, the conical or tubular skeletons of Archaeocyatha,an extinct group of uncertain affinities (possibly sponges), built reefs. Other groups, such as the Bryozoa have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the Scleractinia, arose after the Permian-Triassic extinction that wiped out the earlier rugose corals (as well as many other groups), and became increasingly important reef builders throughout the Mesozoic Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of calcite and have a different symmetry from that of the scleractinian corals, whose skeletons are aragonite. However, there are some unusual examples of well preserved aragonitic rugose corals in the late Permian. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian). [edit] External links Coral Reefs of the Tropics: facts, photos and movies from The Nature Conservancy NOAA Photo Library Reef Environmental Education Foundation Retrieved from "http://en.wikipedia.org/wiki/Reef"
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RIGGING Rigging (from Anglo-Saxon wrigan or wrihan, "to clothe") is, on sailboats and sailing ships, the collection of apparatuses through which the force of the wind is transferred to the ship in order to propel it forward. This includes masts, yardarms, sails, and cordage. Contents [hide] 1 Important Terms and Classifications 2 The Parts of Rigging 2.1 Cordage 2.2 Sails 2.3 Spars 3 See also 4 Authorities 5 References 6 External links [edit] Important Terms and Classifications Rigging is the mechanical sailing apparatus attached to the hull in order to move the boat as a whole. This includes cordage (ropes attached to the spars and sails in order to manipulate their position and shape), sails (aerofoils, usually made of fabric, used to catch the wind), and spars (masts and other solid objects sails are attached to). Cordage is more usually the term for stocks of rope, yarn, or other types line in storage, before it has been put to some use in a vessel, whereafter is commonly referred to as the rigging. In this article, Rigging denotes the full set of cordage, sails and spars, except when it is part of another term (see running rigging and standing rigging). Certain sail-plans are used for certain purposes according to their aerodynamic properties. All sailing vessels are classified according to their hull design and rigging. [edit] The Parts of Rigging [edit] Cordage The term cordage refers to the ropes, called lines, that connect and manipulate sails. Cordage is attached to the spars and sometimes the sails by systems of metal pulleys and clips. The materials chosen for cordage are determined by the strength and weight of the rope. Cordage is divided into two types: running rigging and standing rigging. Standing rigging is cordage which is fixed in position. Standing rigging is almost always between a mast and the deck, using tension to hold the mast firmly in place. Due to its role, standing rigging is now most commonly made of steel cable. It was historically made of the same materials as running rigging, only coated in tar for added strength and protection from the elements. Running rigging is the cordage used to control the shape and position of the sails. Running rigging must be flexible in order to allow smooth movement of the spars and sails, but strong enough for the role it plays. For instance, a halyard, used to hoist heavy yards up and down, must be very strong and durable. On the other hand, a sheet, used to control the orientation of a triangular sail, must be very flexible and smooth, and need only be strong enough to support the tension caused by the wind. [edit] Sails Architectural drawings of the Flying Fish shows a mixture of square and gaff rigs.Sails are fabric aerofoils designed to catch the wind and manipulate the air currents surrounding the vessel. They are attached to spars and rigging in various ways, such as metal clips, rope hoops, or in a luff-groove. Sails are usually rectangular or triangular in shape, which determines their use and placement. Rectangular sails attached to yards, and hanging perpendicular to the keel line are referred to as square sails, because they are "square" to the keel line (not because of their shape); and this type of sailplan is known as square-rigged. Sails hanging along the keel line at rest are known as "fore-and-aft" sails, and the sailplan as fore-and-aft rig; although when under way both square and fore-and-aft sails can fly at a variety of angles relative to the vessel. Fore-and-aft sails may be triangular (see Bermuda rig), or quadrilateral (see Gaff rig). Sail material must be durable against weather, lightweight, and non-porous. Common materials include kevlar, twaron, dacron, and canvas. Sails are classified according to their shape and location. The name of a sail on a square-rigged vessel with multiple masts consists of the mast name and the sail's vertical position. On a three-masted vessel the masts are, from bow to stern, Fore, Main and Mizzen; the "plain" square sails are, bottom to top, Course, Topsail, Topgallant, Royal and Sky. Thus the sail second up the mizzen-mast is the "mizzen topsail", and the third sail up the fore-mast is the "fore topgallant sail". Sails set in other positions, or only in special circumstances, have a variety of other names, for instance: a triangular sail set on a stay might be called a staysail, or jib if the stay in question runs to the prow or bowsprit; sails set either side of square sails to increase sail area in light winds are called studding-sails, qualified by the side and the plain sail name (such as "port topgallant studding-sail", but more likely to be pronounced "port t'gallant stun'sl"); a gaff sail set aft of the mizzen mast may be called a Spanker or Driver. On a modern fore-and-aft rigged boat the largest sail set on the main-mast is known as the mainsail, rather than main course. Sails set forward of the foremost mast are known generically as headsails, and might include jibs, genoas and spinnakers. Fore-and-aft rigged boats setting both a jib and staysail are known as Cutter rigged. More detailed information on sail nomenclature and use can be found in Sails and Sail-plan. [edit] Spars Spars are solid beams used to stabilize and manipulate sails. Masts, yards, booms, gaffs and battens are the most commonly encountered spars. Spars are attached to the sails by systems of clips and cordage designed to allow an appropriate range of motion while maintaining the aerodynamic properties of the sails. Spars can be made of any sufficiently strong material. Flexibility and weight are primary concerns for materials; ideally, spars would be sufficiently rigid to maintain control over the shape of the sail, as well as lightweight in order to maintain a low and stable center of balance. Commonly used materials include wood, steel, aluminum and fiberglass. Masts are spars firmly attached to the deck of the ship. They are the main support for most sails, and all but the most speculative sailboats have at least one, generally set along the keel line. The classification of a mast is determined by its position, size and use. A ship's vertical masts are named, from bow to stern, the fore-mast, the main-mast, the mizzen-mast and the jigger-mast. There may also be a bowsprit, which extends forward past the bow. Masts carrying rectangular or square sails have horizontal yards to stabilize the top and bottom edges of the sails. These yards can rotate around the mast, allowing the sails to be oriented horizontally, usually up to 45 degrees from perpendicular to the keel line. Some yards can be tilted vertically. Cordage associated with yards includes clew lines, bunt lines, the halyard, and lifts. Masts carrying triangular sails have a horizontal boom to stabilize the foot of the sail. It is connected to the base of the mast at the gooseneck, a device designed to allow the boom to pivot about the mast. Cordage associated with booms includes the outhaul, the sheet, the boomvang, and the traveller. Gaffs and battens are spars attached to the mast in a similar manner to the boom, but hinge vertically. Gaffs "joint" sails, allowing for two smaller sails (one above the gaff and one below) rather than one large, triangular sail. Battens are flexible gaffs included within the sail, and are found most notably in Chinese junks. Cordage associated with gaffs and battens includes halyards and the gunter line. On large ships baggywrinkles protect the sail from chafing against the rigging. [edit] See also full rigged ship sail-plan shipbuilding Fore-and-aft rig [edit] Authorities Recommended recent works include James Lees, The Masting and Rigging of English Ships of War, 1625-1860 (Naval Institute Press, 1984), and John Harland, Seamanship in the Age of Sail (Naval Institute Press, 1984). [edit] References This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain. [edit] External links Information on rigging and other parts of sailboats
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RUNNING RIGGING Running rigging is the term for the rigging of a sailing vessel that is used for raising, lowering and controlling the sails - as opposed to the standing rigging, which supports the mast and other spars. Traditionally the running rigging was easily recognized, since for flexibility it was not coated with tar and therefore of a light color, while the standing rigging was tarred for protection and therefore black or dark in color. In the 19th century, running rigging was typically fashioned from Manila rope. On modern vessels, running rigging is likely to be made from polyester and other synthetic fibers, while the standing rigging is frequently made of steel cable, for strength. Some types of running rigging include: halyards, which are used to raise sails (or yards on square-rigged vessels). sheets, which attach to the clews of the sails to control their angle to the wind. downhauls, which lower a sail or a yard, and can be used to adjust the tension on the luff of a sail Cunninghams, which tighten the luff of a sail guys, which control spars topping lifts, which hold up booms or yards barber hauls, which adjust the sheeting angle of a foresail (jib) Older ships (particularly square-rigged vessels) required even more running rigging. Such as: braces, which were used to adjust the fore and aft angle of a yard. tacks, used to haul the clew of a square sail forward. topping lifts, which adjust the up and down angle of a yard. Buntlines, Clewlines, and Leechlines, which allow a square sail to be raised to its yard. Running rigging on modern yachts has been made primarily of polyester/dacron fiber. Some applications, such as halyards and spinnaker guys, have been and continue to be made of flexible wire rope due to chafe and strength issues. In the 1990s several new synthetic fibers have become more common, particularly on racing and other high-performance sailing boats. These fibers include spectra or dyneema, vectran, and technora. [hide]v • d • eSails, spars and rigging Sails Course · Driver · Extra · Genoa · Gennaker · Jib · Lateen · Mainsail · Moonsail · Royal · Skysail · Spanker · Spinnaker · Spritsail · Staysail · Studding · Topgallant · Topsail · Trysail Sail anatomy and materials Clew · Foot · Head · Leech · Luff · Roach · Tack · Dacron · Kevlar · Twaron Spars Boom · Bowsprit · Dolphin striker · Fore-mast · Gaff · Jackstaff · Jigger-mast · Jury rig · Main-mast · Mast · Mizzen-mast · Masthead truck · Spinnaker pole · Topmast · Yard Rigging components Backstay · Block · Boom vang · Braces · Buntlines · Cleat · Clevis pin · Clewlines · Cunningham · Downhaul · Forestay · Gasket · Gooseneck · Guy · Halyard · Outhaul · Parrel beads · Peak · Preventer · Ratlines · Running rigging · Shackle · Standing
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SCHOONER From Wikipedia, the free encyclopedia • Ten things you didn't know about Wikipedia •Jump to: navigation, search Two-masted fishing schoonerFor other uses, see Schooner (disambiguation). A schooner (IPA: [?sku?n?]) is a type of sailing vessel characterized by the use of fore-and-aft sails on two or more masts. Schooners were first used by the Dutch in the 16th or 17th century, and further developed in North America from the time of the American Revolution. Contents [hide] 1 Etymology 2 Construction 3 Operation 4 Famous schooners 5 Gallery 6 References 7 External links [edit] Etymology According to the 1911 Encyclopædia Britannica, the first ship called a schooner was built by builder Andrew Robinson and launched in 1713 from Gloucester, Massachusetts. Legend has it that the name schooner was the result of a spectator exclaiming "Oh how she scoons", scoon being a Scots word meaning to skip or skim over the water. Robinson replied, "A schooner let her be."[1] According to Walter William Skeat, the term schooner comes from the word scoon, while the sch spelling comes from the later adoption of the Dutch and German spellings. [edit] Construction Schooner rigging: 1) Bowsprit 2) Jib, followed by fore staysail 3) (fore)gaff topsail 4) Foresail 5) Main gaff topsail 6) Mainsail 7) End of boom 1793 Newspaper ad for Packet Schooner, Chestertown MDThe schooner sail-plan has two or more masts with the forward mast being shorter or the same height as the rear masts. Most traditionally rigged schooners are gaff rigged, sometimes carrying a square topsail on the foremast and occasionally, in addition, a square fore-course (together with the gaff foresail). Schooners carrying square sails are called square-topsail schooners. Modern schooners may be Marconi or Bermuda rigged. In Bermuda, Bermuda rigged schooners had appeared by the early 19th Century. Known as Ballyhoo schooners, or, along with single masted relatives, with Bermuda or gaff rig, with or without a square topsail, as Bermuda sloops. A memorable example to the last type was HMS Pickle. Some schooner yachts are Bermuda rigged on the mainmast and gaff rigged on the foremast. A staysail schooner has no foresail, but instead carries a main staysail between the masts in addition to the fore staysail ahead of the foremast. A staysail or gaff topsail schooner may carry a fisherman (a four sided fore and aft sail) above the main staysail or foresail, or a triangular mule. Multi-masted staysail schooners usually carried a mule above each stay sail except the fore staysail. Gaff-rigged schooners generally carry a triangular fore-and-aft topsail above the gaff sail on the main topmast and sometimes also on the fore topmast (see illustration), called a gaff-topsail schooner. A gaff-rigged schooner that is not set up to carry one or more gaff topsails is sometimes termed a "bare-headed" or "bald-headed" schooner. A schooner with no bowsprit is known as a "knockabout" schooner. The schooner may be distinguished from the ketch by the placement of the mainsail. On the ketch, the mainsail is flown from the most forward mast; thus it is the main-mast, and the other mast is the mizzen-mast. A two-masted schooner has the mainsail on the aft mast, and therefore the other mast is the fore-mast. Schooners were more widely used in the United States than in any other country. Two masted schooners were and are most common. They were popular in trades that required speed and windward ability, such as slaving, privateering, blockade running and offshore fishing. They also came to be favoured as pilot vessels, both in the United States and in Northern Europe. In the Chesapeake Bay area several distinctive schooner types evolved, including the Baltimore clipper and the pungy. There was no set number of masts for a schooner. A small schooner has two or three masts, but they were built with as many as six (e.g. the wooden six-masted Wyoming) or seven masts to carry a larger volume of cargo. The only seven-masted (steel hulled) schooner, the Thomas W. Lawson, was built in 1902, with a length of 395 ft (120 m), the top of the tallest mast being 155 feet above deck, and carrying 25 sails with 43,000 ft² (4,000 m²) of total sail area. A two or three masted schooner is quite maneuverable and can be sailed by a smaller crew than some other sailing vessels. The larger multi-masted schooners were somewhat unmanageable and the rig was largely a cost-cutting measure introduced towards the end of the days of sail. Essex, Massachusetts was the most significant shipbuilding center for schooners. By the 1850s, over 50 vessels a year were being launched from 15 shipyards and Essex became recognized worldwide as North America’s center for fishing schooner construction. In total, Essex launched over 4,000 schooners, most for Gloucester, Massachusetts fishing industry.[2] [edit] Operation Schooners were used to carry cargo in many different environments, from ocean voyages, to coastal runs and on large inland bodies of water. They were popular in North America, and in their heyday of the late 1800s over 2000 schooners carried cargo back and forth across the Great Lakes. Three-masted "terns" were a favourite rig of Canada's Maritime Provinces. The scow schooner, which used a schooner rig on a flat bottomed, blunt ended scow hull, were popular in North America for coastal and river transport. Three of the most famous racing yachts, America, Atlantic, and Bluenose, were each schooners. [edit] Famous schooners The schooner Bluenose, as depicted on the reverse of the Canadian dimeAdventuress Adventure (schooner) Alma, a scow schooner America La Amistad Atlantic Bluenose Californian Chasseur USS Dolphin (1821) USS Enterprise (1799) Equator Ernestina Esperanto USS Lynx (1814) HMS Pickle Pride of Baltimore The Royalist HMS Sultana Thomas W. Lawson Tole Mour Wawona Wyoming Zodiac
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SHIP Ship From Wikipedia, the free encyclopedia • Find out more about navigating Wikipedia and finding information •Jump to: navigation, search For other uses, see Ship (disambiguation). Italian Full rigged ship Amerigo Vespucci in New York Harbor, 1976A ship is a large watercraft capable of offshore navigation. Ships may be operated by: Governments (military, rescue, research, transportation) Private companies and institutions (transportation, offshore resources, research) Individuals (large yachts, research). Contents [hide] 1 Nomenclature 2 Measuring ships 3 Propulsion 3.1 Pre-mechanization 3.2 Reciprocating steam engines 3.3 Steam turbines 3.3.1 LNG carriers 3.3.2 Nuclear-powered steam turbines 3.4 Reciprocating diesel engines 3.5 Gas turbines 4 Group terminology 5 Some types of ships and boats 6 Some historical types of ships and boats 7 See also 8 External links [edit] Nomenclature A ship usually has sufficient size to carry its own boats, such as lifeboats, dinghies, or runabouts. A rule of thumb used is "a boat can fit on a ship, but a ship can't fit on a boat". Consequently submarines are referred to as "boats", because early submarines were small enough to be carried aboard a ship in transit to distant waters. Other types of large vessels which are traditionally called boats are the Great Lakes freighter, the riverboat, and the ferryboat. Though large enough to carry their own boats and/or heavy cargoes, these examples are designed for operation on inland or protected coastal waters. Often local law and regulation will define the exact size (or the number of masts) which a boat requires to become a ship. During the age of sail, ship signified a ship-rigged vessel, that is, one with three or more masts, usually three, all square-rigged. Such a vessel would normally have one fore and aft sail on her aftermost mast which was usually the mizzen. Almost invariably she would also have a bowsprit but this was not part of the definition. Nautical means related to sailors, particularly customs and practices at sea. Naval is the adjective pertaining to ships, though in common usage it has come to be more particularly associated with the noun "navy". [edit] Measuring ships One can measure ships in terms of overall length, length of the waterline, beam (breadth), depth (distance between the crown of the weather deck and the top of the keelson), draft (distance between the highest waterline and the bottom of the ship) and tonnage. A number of different tonnage definitions exist and are used when describing merchant ships for the purpose of tolls, taxation, etc. In Britain until the Samuel Plimsoll Merchant Shipping Act of 1876, ship-owners could load their vessels until their decks were almost awash, resulting in a dangerously unstable condition. Additionally, anyone who signed onto such a ship for a voyage and, upon realizing the danger, chose to leave the ship, could end up in jail. Samuel Plimsoll, a member of Parliament, realised the problem and engaged some engineers to derive a fairly simple formula to determine the position of a line on the side of any specific ship's hull which, when it reached the surface of the water during loading of cargo, meant the ship had reached its maximum safe loading level. To this day, that mark, called the "Plimsoll Mark", exists on ships' sides, and consists of a circle with a horizontal line through the centre. On the Great Lakes of North America the circle is replaced with a diamond. Because different types of water, (summer, fresh, tropical fresh, winter north Atlantic) have different densities, subsequent regulations required painting a group of lines forward of the Plimsoll mark to indicate the safe depth (or freeboard above the surface) to which a specific ship could load in water of various densities. Hence the "ladder" of lines seen forward of the Plimsoll mark to this day. This is is called the "freeboard mark" or "load line mark"in the marine industry. [edit] Propulsion [edit] Pre-mechanization Ships of the world in 1460, according to the Fra Mauro map.Until the application of the steam engine to ships in the early 19th century, oars propelled galleys or the wind propelled sailing ships. Before mechanisation, merchant ships always used sail, but as long as naval warfare depended on ships closing to ram or to fight hand-to-hand, galleys dominated in marine conflicts because of their maneuverability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans contesting the Battle of Actium. The use of large numbers of cannon from the 16th century meant that maneuverability took second place to broadside weight; this led to the dominance of the sail-powered warship. [edit] Reciprocating steam engines The development of piston-engined steamships was a complex process. Early steamships were fueled by wood, later ones by coal or fuel oil. Early ships used stern or side paddle wheels, later ones used screw propellers. The first commercial success accrued to Robert Fulton's North River Steamboat (often called Clermont) in the US in 1807, followed in Europe by the 45-foot Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the steam surface condenser, which eliminated the use of sea water (salt water) in the ship's boilers. This permits higher steam pressures, and thus the use of higher efficiency multiple expansion (compound) engines. As the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers. [edit] Steam turbines Steam turbines were fueled by coal or later, fuel oil, or nuclear power. The marine steam turbine developed by Sir Charles Algernon Parsons, raised the power to weight ratio. He achieved publicity by demonstrating it unofficially in the 100-foot Turbinia at the Spithead naval review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century and rendered the reciprocating steam engine obsolete, first in warships, and later in merchant vessels. In the early 20th century, heavy fuel oil came into more general use and began to replace coal as the fuel of choice in steamships. Its great advantages were convenience, reduced manning due to removing the need for trimmers and stokers, and reduced space needed for fuel bunkers. In the second half of the 20th century, rising fuel costs almost led to the demise of the steam turbine. Most new ships since around 1960 have been built with diesel engines. The last major passenger ship built with steam turbines was the Fairsky, launched in 1984. Similarly, many steam ships were re-engined to improve fuel efficiency. One high profile example was the 1968 built Queen Elizabeth 2 which had her steam turbines replaced with a diesel-electric propulsion plant in 1986. Most new-build ships with steam turbines are specialist vessels such as nuclear-powered vessels, and certain merchant vessels (notably Liquefied Natural Gas (LNG) and coal carriers) where the cargo can be used as bunker fuel. [edit] LNG carriers New LNG carriers (a high growth area of shipping) continue to be built with steam turbines. The natural gas is stored in a liquid state in cryogenic vessels aboard these ships, and a small amount of 'boil off' gas is needed to maintain the pressure and temperature inside the vessels, to within operating limits. The 'boil off' gas provides the fuel for the ship's boilers, which provide steam for the turbines, the simplest way to deal with the gas. Technology to operate internal combustion engines (modified marine two stroke diesel engines) on this gas has improved however, so such engines are starting to appear in LNG carriers; with their greater thermal efficiency, less gas is burnt. Also, developments have been made in the process of re-liquefying 'boil off' gas, letting it be returned to the cryogenic tanks. The financial returns on LNG are potentially greater than the cost of the marine grade fuel oil burnt in conventional diesel engines, so the re-liquefaction process is starting to be used on diesel engine propelled LNG carriers. Another factor driving the change from turbines to diesel engines for LNG carriers is the shortage of steam turbine qualified sea going engineers. With the lack of turbine powered ships in other shipping sectors, and the rapid rise in size of the worldwide LNG fleet, not enough have been trained to meet the demand. It may be that the days are numbered for the last stronghold for steam turbine propulsion systems, despite all but sixteen of the orders for new carriers at the end of 2004 being for steam turbine propelled ships. [1] [edit] Nuclear-powered steam turbines In these vessels, the reactor heats steam to drive the turbines. Partly due to concerns about safety and waste disposal, nuclear propulsion has become usual only in specialist vessels. In large aircraft carriers, the space formerly used for ship's bunkerage could be used instead to bunker aviation fuel. In submarines, the ability to run submerged at high speed and in relative quiet for long periods holds obvious advantage. A few cruisers have also employed nuclear power; as of 2006, the only ones remaining in service are the Russian Kirov class. An example of a non-military ship with nuclear marine propulsion is the Arktika class icebreaker with 75,000 shaft horsepower. Commercial experiments such as the NS Savannah proved uneconomical compared with conventional propulsion. [edit] Reciprocating diesel engines About 99% of modern ships use diesel reciprocating engines[citation needed]. The rotating crankshaft can power the propeller directly (with slow speed engines), via a gearbox (with medium and high speed engines) or via an alternator and electric motor (in diesel-electric vessels). The reciprocating marine diesel engine first came into use in 1903 when the diesel electric rivertanker Vandal was put in service by Branobel. Diesel engines soon offered greater efficiency than the steam turbine, but for many years had an inferior power-to-space ratio. Diesel engines today are broadly classified according to Their operating cycle: two-stroke or four-stroke. Their construction: Crosshead, trunk, or opposed piston. Their speed. Slow speed: any engine with a maximum operating speed up to 300 revs/minute, although most large 2-stroke slow speed diesel engines operate below 120 revs/minute. Some very long stroke engines have a maximum speed of around 80 revs/minute. The largest, most powerful engines in the world are slow speed, two stroke, crosshead diesels. Medium speed: any engine with a maximum operating speed in the range 300-900 revs/minute. Many modern 4-stroke medium speed diesel engines have a maximum operating speed of around 500 rpm. High speed: any engine with a maximum operating speed above 900 revs/minute. Most modern larger merchant ships use either slow speed, two stroke, crosshead engines, or medium speed, four stroke, trunk engines. Some smaller vessels may use high speed diesel engines. The size of the different types of engines is an important factor in selecting what will be installed in a new ship. Slow speed two-stroke engines are much taller, but the area needed, length and width, is smaller than that needed for four-stroke medium speed diesel engines. As space higher up in passenger ships and ferries is at a premium, these ships tend to use multiple medium speed engines resulting in a longer, lower engine room than that needed for two-stroke diesel engines. Multiple engine installations also give more redundancy in the event of mechanical failure of one or more engines and greater efficiency over a wider range of operating conditions. As modern ships' propellers are at their most efficient at the operating speed of most slow speed diesel engines, ships with these engines do not generally need gearboxes. Usually such propulsion systems consist of either one or two propeller shafts each with its own direct drive engine. Ships propelled by medium or high speed diesel engines may have one or two (sometimes more) propellers, commonly with one or more engines driving each propeller shaft through a gearbox. Where more than one engine is geared to a single shaft, each engine will most likely drive through a clutch, allowing engines not being used to be disconnected from the gearbox while others keep running. This arrangement lets maintenance be carried out while under way, even far from port. [edit] Gas turbines Many warships built since the 1960s have used gas turbines for propulsion, as have a few passenger ships, like the jetfoil. Gas turbines are commonly used in combination with other types of engine. Most recently, the Queen Mary 2 has had gas turbines installed in addition to diesel engines. Due to their poor thermal efficiency at low power (cruising) output, it is common for ships using them to have diesel engines for cruising, with gas turbines reserved for when higher speeds are needed. Some warships and a few modern cruise ships have also used the steam turbines to improve the efficiency of their gas turbines in a combined cycle, where wasted heat from a gas turbine exhaust is utilized to boil water and create steam for driving a steam turbine. In such combined cycles, thermal efficiency can be the same or slightly greater than that of diesel engines alone; however, the grade of fuel needed for these gas turbines is far more costly than that needed for the diesel engines, so the running costs are still higher. [edit] Group terminology Ships may occur collectively as fleets, squadrons, flotillas, or convoys. A collection of ships for military purposes may compose a navy, task force, or an armada. In the past, people counting or grouping disparate types of ship may refer to the individual vessels as bottoms, but this generally refers only to merchant vessels. Groups of sailing ships could constitute a fleet of ___ sail (e.g., "a fleet of 40 sail"). Groups of submarines (particularly German U-boats in the 1940s) formerly hunted in wolf packs. [edit] Some types of ships and boats Semi-submersible MV Blue Marlin carrying USS Cole Semi-submersible The Zhen Hua 1 in Astoria, OregonAircraft carrier Barge Bathyscaphe Bulk carrier bunker Cable Layer Capital ship Cargo ship Catamaran Coaster Container ship Corvette Crane vessel Cruise ship Cruiser Cutter Destroyer Diving support vessel Drillship Dredger Ferry Fishing vessel Floating restaurant Frigate FPSO (Floating Production Storage and Offloading) Guided missile cruiser Hopper barge, Split hopper barge Hovercraft Hydrofoil Icebreaker Jetfoil Junk Landing craft Lake freighter Livestock carrier LNG carrier LPG tanker Lugger Minesweeper Minehunter Ocean liner Packet ship Panamax Passenger ship Reefer (refrigerated ship) Research vessel RO-RO ship (roll on, roll off, Auto carrier) Sailing ship Selfdischargers Semi-submersible Sloop Steamboat Submarine Supertanker Supply boat, Supply ship Survey Vessels Tanker Tender Train ferry Trawler Trireme Tugboat ULCC (Ultra Large Crude Carrier) VLCC (Very Large Crude Carrier) Yacht [edit] Some historical types of ships and boats A two-masted schoonerBarque A sailing vessel with three or more masts, fore-and-aft rigged on only the aftermost. Barquentine A sailing vessel with three or more masts, square-rigged only on the foremast. Battle cruiser A lightly-armoured battleship. Battleship A large, heavily-armoured and heavily-gunned warship. A term which generally post-dates sailing warships. Bilander Bireme An ancient vessel, propelled by two banks of oars. Birlinn Blockade runner A ship whose current business is to slip past a blockade. Brig A two-masted, square-rigged vessel. Brigantine A two-masted vessel, square-rigged on the foremast and fore-and-aft rigged on the main. Caravel A much smaller, two, sometimes three-masted ship. Carrack Clipper A fast multiple-masted sailing ship, generally used by merchants because of their speed capablities. Cog Collier A vessel designed for the coal trade. Dreadnought An early twentieth century class of battleship. Dromons are the precursors to galleys. East Indiaman An armed merchantman belonging to one of the East India companies (Dutch, British etc.) Fire ship A vessel of any sort, set on fire and sent into an anchorage with the aim of causing consternat
on and destruction. The idea is generally that of forcing an enemy fleet to put to sea in a confused, therefore vulnerable state. Fleut A Dutch-made vessel from the Golden Age of Sail. It had multiple decks and usually three square-rigged masts. It was usually used for merchant purposes. Galleass A sailing and rowing warship, equally well suited to sailing and rowing. Galleon A sixteenth century sailing warship. Galley A warship propelled by oars with a sail for use in a favourable wind. Galliot Ironclad A wooden warship with external iron plating. Knarr A type of Viking trade ship Liberty ship An American merchant ship of the late Second World War period, designed for rapid building in large numbers. (The earliest class of welded ships.) Longship A Viking raiding ship Man of war A sailing warship. Monitor A small, very heavily gunned warship with shallow draft. Designed for land bombardment. Paddle steamer A steam-propelled, paddle-driven vessel, a name commonly applied to nineteenth century excursion steamers. Pantserschip A Dutch ironclad. By the end of the nineteenth century, the name was applied to a heavy gunboat designed for colonial service. Penteconter An ancient warship propelled by 50 oars, 25 on each side. Pram A small dinghy, originally of a clinker construction and called in English, as in Danish, a praam. The Danish orthography has changed so that it would now be a pråm in its original language. It has a transom at both ends, the forward one usually small and steeply raked in the traditional design. Q-ship A commerce raider camouflaged as a merchant vessel. Quinquereme An ancient warship propelled by three banks of oars. On the upper row three rowers hold one oar, on the middle row - two rowers, and on the lower row - one man to an oar. Schooner A fore and aft-rigged vessel with two or more masts of which the foremast is shorter than the main. Shallop A large, heavily built, sixteenth century boat. Fore and aft rigged. More recently it has been a poetically frail open boat. Slave ship A cargo boat specially converted to transport slaves. Small Waterplane Area Twin Hull (SWATH) A modern ship design used for Research Vessels and other purposes needing a steady ship in rough seas. Steamship A ship propelled by a steam engine. Ship of the line A sailing warship of first, second or third rate. That is, with 64 or more guns. Before the late eighteenth century, fourth rates (50-60 guns) also served in the line of battle. Torpedo boat A small, fast surface vessel designed for launching torpedoes. Tramp steamer A steamer which takes on cargo when and where it can find it. Trireme An ancient warship propelled by three banks of oars. Xebec Victory ship
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SHOAL Shoal From Wikipedia, the free encyclopedia (Redirected from Sandbar)• Have questions? Find out how to ask questions and get answers. •Jump to: navigation, search For other uses, see Shoal (disambiguation). Sandbar between St. Agnes, Isles of Scilly and Gugh in Cornwall A tidal sandbar connecting the islands of Waya and Wayasewa of the Yasawa Islands, FijiA shoal is a somewhat linear landform within or extending into a body of water, typically comprised of sand, silt or small pebbles. Alternatively termed sandbar or sandbank, a bar is characteristically long and narrow (linear) and develops where a stream or ocean current promote deposition of granular material, resulting in localized shallowing (shoaling) of the water. Bars can appear in the sea, in a lake, or in a river. They are typically composed of sand, although could be of any granular matter that the moving water has access to and is capable of shifting around (for example, soil, silt, gravel, cobble, shingle, or even boulders). The grain size of the material comprising a bar is related to the size of the waves or the strength of the currents moving the material, but the availability of material to be worked by waves and currents is also important. The term bar can apply to landform features spanning a considerable range in size, from a length of a few meters in a small stream to marine depositions stretching for hundreds of kilometres along a coastline, often called barrier islands. In a nautical sense, a bar is a shoal, similar to a reef: a shallow formation of (usually) sand that is a navigation or grounding hazard. It therefore applies to a silt accumulation that shallows the entrance to or the course of a river or creek. Contents [hide] 1 Sandbars and longshore bars 2 Shoals as geological units 3 Federal Laws 4 Examples 5 See also 6 References [edit] Sandbars and longshore bars A sandbar off of Suffolk County, Long Island, New York, August 2006. Shoals in the Mississippi River at Arkansas and Mississippi.Bars that occur at or off the shoreline of a sea or a lake are related to beaches and might be considered offshore features of a beach (Bascom, 1980). At times when larger waves attack the beach berm, some of the beach material is redistributed offshore to become a longshore bar or sandbar, possibly visible at low tide. This bar forms (sometimes seaward of a trough) where the waves are breaking, because the breaking waves set up a shoreward current with a compensating counter-current along the bottom. Sand carried by the offshore moving bottom current is deposited where the current reaches the wave break (Bascom, 1980). Other longshore bars may lie further offshore, representing the break point of even larger waves, or the break point at low tide. [edit] Shoals as geological units In addition to longshore bars discussed above that are relatively small features of a beach, the term shoal can be applied to larger geological units that form off a coastline as part of the process of coastal erosion. These include spits and baymouth bars that form across the front of embayments and rias. A tombolo is a bar that forms an isthmus between an island or offshore rock and a mainland shore. The largest of the geological units of this kind is a barrier island, such as occur along the East Coast of the United States, along the Gulf coast, along the southern coast of Belize and many other locations worldwide. In places of re-entrance along a coastline (such as inlets, coves, rias, and bays), sediments carried by a longshore current will fall out where the current dissipates, forming a spit. An area of water isolated behind a large bar is called a lagoon. Over time, lagoons may silt up, becoming salt marshes
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SONAR 1 Sonar Propagation By virtue of the fact that the speed that acoustic waves travel at depends on the properties of the medium (i.e. sea water), the propagation of sonar will be complicated. So complicated in fact that it will be impossible to accurately predict without the use of a computer model. However, sonar systems rely heavily on operator input and control to maximize their performance. Many of the decisions made regarding the maneuvering of the ship carrying the sonar system will also affect the sonar's performance. Therefore a detailed knowledge of the salient features of sonar propagation is essential to its successful employment. We begin with a simple model for the transmission loss. Transmission Loss Formula Transmission loss (TL) can be predicted, to a very rough degree, solely on the basis of a few factors. These factors are range, and frequency. Range Effect The simplest case, which is the identical case used in electro-optics and radar, is to assume all of the acoustic energy is uniformly distributed in all directions. In sonar this is termed spherical spreading loss, since the intensity will fall off proportional to the surface area of a sphere. Figure 1. Spherical spreading. Since the area over which the energy is distributed at range, R, is 4pR2, the ratio of any two intensity levels at different ranges can be computed. If we take the decibel equivalent, and take the first range as one meter, which happens to be where the source level is defined, we obtain the spherical spreading loss f part of TL: TLspherical = -10 Log { I(R)/I(1 m)} = -10 Log{1/R2} TLspherical = 20 Log(R) . The negative sign was included since TL is defined to be positive quantity, and is subtracted in the SNR equations. When the acoustic energy reaches either the surface or the bottom of the ocean, it is generally reflected back. A long range, all of the acoustic energy will tend to confined between two planes, one at the surface and the other at the bottom. Therefore, the energy can no longer spread out like the spherical spreading case, but now becomes cylindrical spreading. Figure 2. Cylindrical spreading. The area over which the energy is distributed now varies directly with range, R. The common factors will cancel, and the transmission loss between two ranges will be 10 Log( R). Explicitly this means SPL(R2) = SPL(R1) - 10 Log(R2/R1). It would be nice if we could choose R1 to be one meter in which case SPL(R1) = SL, but this would be incorrect. That would be akin to claiming that the spreading losses where cylindrical starting from one meter. Clearly, in regions where the water depth is larger than the range, the spreading must be spherical. The question now becomes: at what range does the spreading loss transition between the spherical and cylindrical case. If the source where located exactly in the middle (halfway between the surface and bottom), then it seems plausible to make the transition when the range is one-half the water depth since this is when the surface of the sphere will just touch the bottom and top. The transition range will depend on the location of the source and the depth of water. For purposes we assume the transition range to be 1000 m, since the average ocean depth is about 2000 m. At 1000 m, the transmission loss due solely to spherical spreading will be 60 dB. Taking this as the starting point for cylindrical spreading, we can patch the two equations together by adding 30 dB to the 10 Log(R) spreading. This is proven below: TLspherical(at 1000 m) = 20 Log (1000) = 60 dB TLcylindrical(at 1000m) = 10 Log(1000) = 30 dB If we wish to apply the TLcylindrical formula starting at 1 m, then we must add the difference at 1000m, therefore TLcylindrical (R) = 10 Log(R) + 30 dB. (valid when R > 1000 m) At ranges of less than 1000 m, you must use the spreading spreading loss formula, TLspherical = 20 Log(R). absorption/scattering Like air in electro-optics, the intervening water between the source and receiver will either absorb some of the acoustic energy passing through it. The dependence on range will be identical to Bougher's law, but now in decibel form: Tlabs = - 10 Log( e-bR) = (10 b)R where b is the extinction coefficient. The factor of 10 and a unit conversion into km is absorbed in the definition of the absorption coefficient, a b/100, therefore Tlabs = a R. where a has units of dB/km. The absorption coefficient has a strong frequency dependence, meaning much greater losses at higher frequency. The absorption coefficient can be calculated from a formula: where f is in kHz, and the result for a is in dB/km. or using a graph: Figure 3. Absorption coefficient as a function of frequency. Other losses Many other things can happen to the acoustic wave as it propagates. For example the energy may scatter off particles or biologics. Energy will be lost upon reflection from the surface and bottom. And lastly, by but far the greatest factor of all will be the change in the propagation due to the variations in the speed with temperature, depth and salinity. The change in speed will tend to distort the perfect spherical or cylindrical shape of the wave front. This does not, however, always result in greater transmission losses. As we shall soon see, there are many conditions which tend to concentrate acoustic energy resulting in a lower than expected transmission loss. All of these factors just discussed can be lumped into a single term, A, called the transmission loss anomaly. This is surely artificial and is only used in order to be able to write a complete equation for TL. All deviations from the predicted result can be explained away in the term A. The equation so written is TL = 10 Log(R) + 30 + aR + A If you ignore, the last two terms, the range dependence is very straight forward, and can be used to generate some rules of thumb: TL 60 dB at 1 km TL 70 dB at 10 km TL 80 dB at 100 km. This is based on nothing but the spherical and cylindrical spreading losses, assuming the source is exactly in the middle of 2000 m deep water. What one finds in practice, are variations about these baseline numbers. This can also be shown in graphical form, TL vs. range. Figure 4. Geometrical transmission loss curve. Propagation Paths To gain further insight into how the environment can affect propagation, we first study how the propagation speed varies in the ocean. The Sound Velocity Profile (SVP) The largest variation is the speed of sound in water occurs with changes is depth. Obviously the pressure increases with depth causing a uniform increase of +1.7 m/s for every 100 m. Furthermore, the ambient temperature changes with depth. A plot of propagation speed (velocity) as a function of depth, is called the sound velocity profile (SVP), and it is the fundamental tool for predicting how sound will travel. Neglecting salinity, the SVP can be obtained from sampling the ambient temperature at various depths (the pressure contribution never varies). An inexpensive probe to do this is called an expendable bathythermograph (XBT). The resulting SVP looks like this: Figure 5. Oean layers. The SVP reveals some common structure to the ocean. The water can be divided into three vertical regions. The surface (seasonal) layer is at the top and is the most variable part. As the name suggests, the profile will changes depending on the time of day (diurnal variation) and the season (seasonal variation). During the day, the heat from the sun (insolation) causes the water at the very top to be warmer than the water below. Since the condition of warm over cold is stable, the condition is quite common. Late in the afternoon, particularly on a bright day, the surface temperture will be the greatest and so one would expect the greatest gradient (change with depth). Figure 6. Diurnal variation in SVP. The main thermocline connects the seasonal layer with the uniformly cold water found deep in the ocean. Below about 500 m, all of the world's oceans are at about 34o F. The positive gradient in the deep isothermal region is solely due to the pressure effect. In the summer, the seasonal layer tends to have a strongly negative gradient, for the same reason as given to explain the diurnal variation. So the summer profile looks like: Figure 7. Summer SVP. In winter, the water is generally warmer than the air. A lot of heat is lost through advection and radiation. However, one would not expect to see cold water setting on top of warm water for very long. Convection brings the warm water to the surface destroying the effect. The surface layer tends to be closer to isothermal than anything else. Additionally, strong winter storms and their large waves frequently mix the surface layer to a depth of up to 100 m. For the nearly isothermal surface layer, one could expect a weakly positive gradient above the main thermocline. Figure 8. Winter SVP. Ray Tracing The change of propagation speed with depth will manifest itself through refraction of the sound. A graphical method of illustrating the effects is called ray tracing. The basic idea is to draw lines perpendicular to the wave fronts and follow their paths. For a typical sonar array, these lines start equally spaced within the beam capability of the array (discussed in the next chapter). Figure 9. Ray tracing. As the rays go deeper, they begin to refract. Recall how differences in the index of refraction (which are a measure of the propagation speed) affected electromagnetic waves. As the rays move into a medium which has a slower propagation speed, they tend to become more vertical. On the whole, the rays will deflect downward in a negative gradient. Figure 10. Negative SVP gradient. As you might expect, the opposite effect occurs when the gradient is positive. As the rays enter deeper water the propagation speed increases and the rays bend upwards. Figure 11. Positive SVP gradient. All of the rays will be deflected upwards. When the rays reach the surface, the will be reflected back downwards and the same process begins again. Naturally, some of the energy is lost and the reflection, but the overall effect is to trap the sound in a relatively small layer below the surface. The sound does not reach the deeper regions, so the transmission less than you would expect for cylindrical spreading. This effect is called a surface duct. Figure 12. Surface duct. The other common propagation modes occur during combinations of positive and negative gradients. A positive gradient over a negative gradient produces a special kind of propagation, where the rays split at the boundary which is called the layer. The depth of maximum sound velocity which ocurs on the layer is called the layer depth (LD). Figure 13. Sonic layer. Above the layer, the positive gradient will produce a surface duct as previously described. When rays penetrate below the layer, they are deflected downward. Therefore, the rays diverge above and below the layer. Beyond a certain minimum range, the rays from the source will never reach locations just below the layer. This is called the shadow zone. It is a favored depth for submarines to operate at for just this very reason. The optimum depth to operate at, called best depth (BD), is a function of the layer depth. The best depth can be calculated from For the case where the negative gradient is over the positive, rays which originate at the boundary will be deflected back towards the middle, regardless if they go up or down. This forms a sound channel, where the rays are then confined to the small region above and below the axis, called the sound channel axis. Figure 14. Sound channel. The sound channel will not work for rays that begin at the surface, like in the other cases. The source must be located near the axis. Several sonar systems have features which allow them to be placed near the sound channel axis. For example, sonobouys, which are small self-contained sonar systems, have a setting which places them at a typical sound channel axis depth. Another special type of propagation occurs when the water is so deep that no sound can reach the bottom without being deflected upwards by the normal positive gradient found in the deep isothermal layer. This situation requires a minimum of 200 m of depth excess which is defined as depth excess: the distance from the lower boundary of the sound channel to the bottom. When all of the sound rays are returned to near the surface, they tend to converge into a small region. Therefore the sound pressure level is increased dramatically in this region known as a convergence zones (CZ). Figure 15. Convergence zone. The convergence zone tends to be at large distances, typically 20-30 nm from the source. It is possible to have multiple convergence zones, which will occur at regular intervals. For example, if the first CZ is at 30 nm, the second CZ would be at 60 nm. The CZ is only a few miles wide, and therefore, contacts which are acquired through convergence zones tend to appear and disappear quickly. It may be possible for a ship to have a rather limited sonar range due to regular transmission losses but multiple convergence zones. These zones form protective rings about the ship. A hostile submarine closing in on the ship would be detected as it passes through the various convergence zones, thereby alerting the ship to its presence. The ship could then deploy mobile ASW assets like a helicopter to handle the submarine. Figure 16. Annulus of CZ. Finally the last type of propagation occurs in when the sound is strongly reflected from the ocean floor. The rays tends to converge near the surface, resulting in a reduced transmission loss. This is called bottom bounce propagation. Rays from bottom bounce can be identified from the others because of the larger angle of incidence. Typical bottom bound comes into the sonar at angles of more than 30o from horizontal. Figure 17. Bottom bounce. Only certain ocean floor conditions are conducive to bottom bounce propagation. Flat and hard ocean floors tend to be the best. Soft mud, on the other hand is the worst. Figure of Merit Because the propagation of acoustics waves in the ocean is fairly complicated, the use of a formula for transmission loss is of limited accuracy. Computer models can be used to produce much more accurate plots of TL as a function of range, known as transmission loss curves. Here is a typical TL curve showing some of the features just discussed: Figure 18. Typical TL curve. In comparision to the geometrical TL (spherical and cylindrical spreading losses) you will note there are certain ranges where the TL actually goes down with increased range. These are locations where the refraction effects of the ocean cause the sound rays to concentrate. This example illustrates the effect of bottom bound and CZ. Given an accurate transmission loss curve, we are now in a position to estimate the maximum detection range of a sonar system. Recall that detection is possible whenever SNR < DT. To solve for range, we only need rearrange terms to isolate the range dependence. For the passive case, define figure of merit, FOM FOMpassive SL + DI - NL - DT Now the detection criterion becomes FOM > TL. Which leads to the following interpretation: Figure of Merit (FOM) is the maximum transmission loss the system can have and still be able to detect the target (at 50% of the time). If FOM is known, then the maximum range can be determined by plotting the FOM as a horizontal line on the TL curve. All ranges where the FOM > TL (remember that TL is increasing in the down direction), are detectable. Figure 19. Determining maximum detection range from FOM. In this example, the FOM = 75 dB. From the graph, it is apparent that FOM > TL everywhere less than 18 km, which is the maximum detection range. FOMactive SL + TS + DI - NL - DT For active systems, there are (at least) two complications. First the FOM is modified so that Secondly, the transmission loss is incurred twice, as the sound travels to the target and back. You could use a separate curve with twice the TL vs. range, or alternatively, use one-half the FOM, which is the preferred method. So for active systems, the detection criterion is: FOM > 2 TL or FOM/2 > TL. Therefore, you calculate FOM and then plot FOM/2 on the TL curve to obtain range in the same manner.
Territorial waters Territorial waters From Wikipedia, the free encyclopedia • Ten things you didn't know about images on Wikipedia •Jump to: navigation, search Map of Sealand and the United Kingdom, with territorial water claims of 3 NM and 12 NM shown.Territorial waters, or a territorial sea, is a belt of coastal waters extending at most twelve nautical miles (but possibly less, at the coastal country's discretion) from the mean low water mark of a littoral state that is regarded as the sovereign territory of the state, except that foreign ships (both military and civilian) are allowed innocent passage through it.[1] A sovereign state has complete jurisdiction over internal waters, where not even innocent passage is allowed. Territorial waters extend up to 12 nautical miles (22.224 km) from the mean low water mark adjacent to land, or from internal waters, as per the 1982 United Nations Convention on the Law of the Sea. The mean low water mark may be an unlimited distance from permanently exposed land, provided that some portion of elevations exposed at low tide but covered at high tide (like mud flats) is within 12 nautical miles of permanently exposed land. Completely enclosed seas, lakes, and rivers are considered internal waters, as are waters landward of lines connecting fringing islands along a coast or landward of lines across the mouths of rivers that flow into the sea. Bays are defined as indentations between headlands having an area greater than that of a semicircle. If they do not exceed 24 nautical miles (about 44 km) between headlands then they are internal waters; if their entrance is wider, then that portion landward of a 24 nautical miles straight line that touches opposite low-water marks across the bay positioned to contain the greatest water area are internal waters. All archipelagic waters within the outermost islands of an archipelagic state like Indonesia or the Philippines are also considered internal waters. Control over a contiguous zone, up to an additional 24 - N nautical miles beyond the territorial sea, where the territorial sea is N nautical miles wide, N?12, is permitted by a coastal nation to "prevent infringement of its customs, fiscal, immigration or sanitary laws and regulations". The United States invoked a contiguous zone on 24 September 1999.[2] Conflicts still occur whenever a coastal nation claims an entire gulf as its territorial waters while other nations only recognize the more restrictive definitions of the UN convention. Two recent conflicts occurred in the Gulf of Sidra where Libya has claimed the entire gulf as its territorial waters and the U.S. has twice violently enforced freedom of navigation rights (Gulf of Sidra incident (1981), Gulf of Sidra incident (1989)). An exclusive economic zone extends for 200 nautical miles (370 km) beyond the baselines of the territorial sea, thus it includes the territorial sea and its contiguous zone.[3] A coastal nation has control of all economic resources within its exclusive economic zone, including fishing, mining, oil exploration, and any pollution of those resources. However, it cannot regulate or prohibit passage or loitering above, on, or under the surface of the sea, whether innocent or belligerent, within that portion of its exclusive economic zone beyond its territorial sea. Before 1982, coastal nations arbitrarily extended their territorial waters in an effort to control activities which are now regulated by the exclusive economic zone, such as offshore oil exploration or fishing rights (see Cod War). Indeed, the exclusive economic zone is still popularly, though erroneously, called a coastal nation's territorial waters. The continental shelf of a coastal nation extends out to its continental margin, but at least 200 nautical miles from the baselines of its territorial sea. The continental margin is defined by a series of points not more than 60 nautical miles (111 km) apart where the thickness of sedimentary rocks is at least one per cent of the height of the continental shelf above the foot of the continental slope, but not more than 60 nautical miles inshore from it. The foot of the continental slope is where the maximum change in the gradient of the seabed occurs. The continental margin cannot exceed 350 nautical miles (648 km) beyond the baselines of the territorial sea or 100 nautical miles (185 km) beyond the 2,500-metre depth, unless "natural components of the continental margin, such as its plateaux, rises, caps, banks and spurs" but not submarine ridges are farther out. The coastal nation has control of all resources on or under its continental shelf, living or not, but no control over any living organisms above the shelf that are beyond its exclusive economic zone.[4] Ireland has become one of the first countries to define its continental shelf in accordance with the UN convention.[5] Pirate radio broadcasting from artificial marine fixtures or anchored ships can be controlled by the affected coastal nation or other nations wherever that broadcast may originate, whether in the territorial sea, exclusive economic zone, the continental shelf or even on the high seas.[6] Thus a coastal nation has total control over its internal waters, slightly less control over territorial waters, and ostensibly even less control over waters within the contiguous zones. However, it has total control of economic resources within its exclusive economic zone as well as those on or under its continental shelf. From the eighteenth century until the mid twentieth century, the territorial waters of the British Empire, the United States, France and many other nations were three nautical miles (6 km) wide. Originally, this was the length of a cannon shot, hence the portion of an ocean that a sovereign state could defend from shore. However, Iceland claimed two nautical miles (4 km), Norway claimed four nautical miles (7 km), and Spain claimed six nautical miles (11 km) during this period. During incidents such as nuclear weapons testing and fisheries disputes some nations arbitrarily extended their maritime claims to as much as fifty or even two hundred nautical miles. Since the late 20th century the "12 mile limit" has become almost universally accepted. The United Kingdom extended its territorial waters from three to twelve nautical miles in 1987. Throughout this article, distances measured in nautical miles are exact legal definitions, while those in kilometres are approximate conversions that are not stated in any law or treaty.
TRAMP STEAMER A tramp steamer, or tramp for short, is any ship which does not have a fixed schedule or published ports of call. (As opposed to freight liners), tramp ships trade on the spot market with no fixed schedule or itinerary/ports-of-call(s). Steamers are infrequently seen today, as steam has largely been replaced by diesel engines -- which can be operated more economically. Because of this the term tramp freighter is sometimes used. The term is derived from an old meaning of "tramp" as itinerant beggar or vagrant, and is first documented in the 1880s, along with "ocean tramp" (at the time many sailing vessels engaged in irregular trade as well). There are several tramp charter types for hiring vessels.
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United nations Convention on the Law of the sea From Wikipedia, the free encyclopedia • Learn more about using Wikipedia for research •Jump to: navigation, search For maritime law in general see Admiralty law. United Nations Convention on the Law of the Sea Opened for signature December 10, 1982 in Montego Bay (Jamaica) Entered into force November 16, 1994[1] Conditions for entry into force 60 ratifications Parties 155[1] International Ownership Treaties Antarctic Treaty System Law of the Sea Outer Space Treaty Moon Treaty International waters Extraterrestrial real estate The United Nations Convention on Law of the Sea (UNCLOS), also called the Law of the Sea Convention and referred to by its opponents as the Law of the Sea Treaty (LOST), is the international agreement that resulted from the third United Nations Convention on the Law of the Sea that took place from 1973 through 1982 with modifications that were made by the 1994 Agreement on Implementation. The Law of the Sea Convention is a set of rules for the use of the world's oceans, which cover 70 percent of the Earth's surface. The Convention was concluded in 1982 to replace four 1958 treaties that were out of date. UNCLOS came into force in 1994, and to date, 154 countries and the European Community have joined the Convention. The United States has not joined because it claims this treaty is unfavorable to America's economy and security. The Convention defines the rights and responsibilities of nations in their use of the seas, establishes clear guidelines for businesses, protects the environment, and improves the management of marine natural resources. The events the term refers to are the (First) United Nations Convention on Law of the Sea, the Second United Nations Convention on Law of the Sea, and the Third United Nations Convention on Law of the Sea. The treaty resulting from the Third United Nations Convention on Law of the Sea also bears the name United Nations Convention on Law of the Sea. While the Secretary General of the United Nations receives instruments of ratification and accession and the UN provides support for meetings of states party to the Convention, the UN does not have an operational role in the implementation of the Convention. There is, however, a role played by autonomous intergovernmental organizations such as the Intergovernmental Maritime Organization, the International Whaling Commission, and the International Seabed Authority that was established by the Convention. Contents [hide] 1 Historical background 2 UNCLOS I 3 UNCLOS II 4 UNCLOS III 5 Part XI 6 Signature and ratification 7 United States non-ratification 7.1 Debate 7.2 Arguments 7.3 Latest developments 8 References 9 See also 10 External links [edit] Historical background The LOS was needed owing to the weakness of the older 'freedom of the seas' concept, dating from the 17th century: national rights were limited to a specified belt of water extending from a nation's coastlines, usually three nautical miles, according to the 'cannon shot' rule developed by the Dutch jurist Cornelius Bynkershoek. All water beyond national boundaries was considered international waters - free to all nations, but belonging to none of them (the mare liberum principle promulgated by Grotius). In the early 20th century many nations expressed a need to extend national claims, in order to include mineral resources, to protect fish stocks, and to have the means to enforce pollution controls. This was recognized by the League of Nations, and a conference was held in 1930 at the Hague, but did not result in any agreements. One nation that reflected the customary international law principle of a nation's right to protect its natural resources was the United States, when in 1945 President Truman extended his nation's control, to cover all the natural resources of their continental shelf. Other nations were quick to emulate the USA. Between 1946 and 1950, Argentina, Chile, Peru, and Ecuador all extended their sovereign rights to a distance of 200 nautical miles—so as to cover their Humboldt Current fishing grounds. Other nations extended their territorial seas to 12 nautical miles. By 1967 only 25 nations still used the old three nautical miles limit, 66 nations had set a 12 nautical miles territorial limit, and eight had set a 200 nautical miles limit. For the latest table of maritime claims, as compiled by the United Nations, see [2]. According to that table, as of July 27, 2007, only a handful of countries use the old 3 miles limit (Jordan, Palau, and Singapore). It is also used in certain Australian islands, an area of Belize, some Japanese straits, certain areas of Papua New Guinea, and a few UK dependencies, such as Anguilla. [edit] UNCLOS I In 1956, the United Nations held its first Conference on the Law of the Sea (UNCLOS I) at Geneva, Switzerland. UNCLOS I resulted in four treaties concluded in 1958: Convention on the Territorial Sea and Contiguous Zone, entry into force: 10 September 1964 Convention on the Continental Shelf, entry into force: 10 June 1964 Convention on the High Seas, entry into force: 30 September 1962 Convention on Fishing and Conservation of Living Resources of the High Seas, entry into force: 20 March 1966 Although UNCLOS I was considered a success, it left open the important issue of breadth of territorial waters. [edit] UNCLOS II The United Nations followed this in 1960 with its second Conference on the Law of the Sea (“UNCLOS II”). UNCLOS II did not result in any international agreements. During the six-week conference at Geneva, UNCLOS II did not achieve much. Generally speaking, the developing countries participated only as clients, allies, or dependents of United States or the former Soviet Union; there was no voice for countries of the third world or the developing nations. [edit] UNCLOS III Sea areas in international rightsThe issue of varying claims of territorial waters was raised in the UN in 1967 by Arvid Pardo, of Malta, and in 1973 the Third United Nations Conference on the Law of the Sea was convened in New York to write a new treaty covering the oceans. The conference lasted until 1982 and over 160 nations participated. The conference was conducted under a process of consensus rather than majority vote in an attempt to reduce the possibility of groups of nation-states dominating the negotiations. The convention came into force on November 16, 1994, one year after the sixtieth state, Guyana, signed it. The convention introduced a number of provisions. The most significant issues covered were setting limits, navigation, archipelagic status and transit regimes, exclusive economic zones (EEZ), continental shelf jurisdiction, deep seabed mining, the exploitation regime, protection of the marine environment, scientific research, and settlement of disputes. The convention set the limit of various areas, measured from a carefully defined baseline. (Normally, a sea baseline follows the low-water line, but when the coastline is deeply indented, has fringing islands or is highly unstable, straight baselines may be used). The areas are as follows: Internal waters Covers all water and waterways on the landward side of the baseline. The coastal nation is free to set laws, regulate any use, and use any resource. Foreign vessels have no right of passage within internal waters. Territorial waters Out to 12 nautical miles from the baseline, the coastal state is free to set laws, regulate any use, and use any resource. Vessels were given the right of "innocent passage" through any territorial waters, with strategic straits allowing the passage of military craft as "transit passage", in that naval vessels are allowed to maintain postures that would be illegal in territorial waters. "Innocent Passage" is defined by the convention as passing through waters in expeditious and continuous manner, which is not “prejudicial to the peace, good order or the security” of the coastal state. Fishing, polluting, weapons practice, spying are not “innocent.” Nations can also temporarily suspend innocent passage in specific areas of their territorial seas, if doing so is essential for the protection of its security. Archipelagic waters The convention set the definition of Archipelagic States in Part IV, which also define how the state can draw its territorial borders. A baseline is drawn between the outermost points of the outermost islands, subject to these points being sufficiently close to one another. All waters inside this baseline is described as Archipelagic Waters and are included as part of the state's territorial waters. Contiguous zone Beyond the 12 nautical mile limit there was a further 12 nautical miles or 24 nautical miles from the territorial sea baselines limit, the contiguous zone, in which area a state could continue to enforce laws regarding activities such as smuggling or illegal immigration. Exclusive economic zones (EEZ) Extends 200 nautical miles from the baseline. Within this area, the coastal nation has sole exploitation rights over all natural resources. The EEZ were introduced to halt the increasingly heated clashes over fishing rights, although oil was also becoming important. The success of an offshore oil platform in the Gulf of Mexico in 1947 was soon repeated elsewhere in the world, by 1970 it was technically feasible to operate in waters 4000 metres deep. Foreign nations have the freedom of navigation and overflight, subject to the regulation of the coastal states. Foreign states may also lay submarine pipes and cables. Continental Shelf Continental shelf is defined as natural prolongation of the land territory to the continental margin’s outer edge, or 200 nautical miles from the coastal state’s baseline, whichever is greater. State’s continental shelf may exceed 200 nautical miles until the natural prolongation ends, but it may never exceed 350 nautical miles, or 100 nautical miles beyond 2,500 meter isobath, which is a line connecting the depth of 2,500 meters. States have the right to harvest mineral and non-living material in the subsoil of its continental shelf, to the exclusion of others. Aside from its provisions defining ocean boundaries, the convention establishes general obligations for safeguarding the marine environment and protecting freedom of scientific research on the high seas, and also creates an innovative legal regime for controlling mineral resource exploitation in deep seabed areas beyond national jurisdiction, through an International Seabed Authority. Landlocked states are given a right of access to and from the sea, without taxation of traffic through transit states. [edit] Part XI Part XI of the Convention provides for a regime relating to minerals on the seabed outside any state's territorial waters or EEZ. It establishes an International Seabed Authority (ISA) to authorize seabed exploration and mining and collect and distribute the seabed mining royalty. [edit] Signature and ratification ratified signed, but not yet ratified did not signOpened for signature - December 10, 1982. Entered into force - November 16, 1994. Countries that have signed, but not yet ratified - (24) Afghanistan, Bhutan, Burundi, Cambodia, Central African Republic, Chad, Colombia, Republic of the Congo, Dominican Republic, El Salvador, Ethiopia, Iran, North Korea, Liberia, Libya, Liechtenstein, Malawi, Niger, Rwanda, Swaziland, Switzerland, Thailand, United Arab Emirates, United States. Countries that have not signed - (17) Andorra, Azerbaijan, Ecuador, Eritrea, Israel, Kazakhstan, Kyrgyzstan, Peru, San Marino, Syria, Tadjikistan, Timor-Leste, Turkey, Turkmenistan, Uzbekistan, Vatican City, Venezuela. [edit] United States non-ratification The neutrality of this article is disputed. Please see the discussion on the talk page. Please do not remove this message until the dispute is resolved. The United States strongly objected to the provisions of Part XI of the Convention, on several grounds. The US felt that the provisions of the treaty were not free-market friendly and were designed to favor the economic systems of the Socialist states. The US felt that the provisions could potentially result in the ISA receiving large revenues from seabed mining, and that there was insufficient controls over what these revenues could be used for. It was concerned that the ISA would become a bloated and expensive bureaucracy even if seabed mining never proved to be economically feasible. Due to Part XI, the US refused to sign the UNCLOS, although they expressed their agreement with the remaining provisions of the Convention. They also expressed the view that even not as a party, it considered many of the remaining provisions as binding upon the United States as a statement of customary international law which it had accepted. Revision of the LOS Convention From 1983 to 1990, the United States followed a policy of accepting all but Part XI as customary international law while attempting to establish an alternative regime for exploitation of the minerals of the deep seabed. An agreement was made with other seabed mining nations and licenses were granted to four international consortia. Concurrently, the Preparatory Commission was established to prepare for the eventual coming into force of the Convention-recognized claims by applicants, sponsored by signatories of the Convention. Overlaps between the two groups were resolved, but a decline in the demand for minerals from the seabed made the seabed regime significantly less relevant. In addition, the decline of Socialism and the fall of Communism in the late 1980s had removed much of the support for some of the more contentious Part XI provisions. In 1990, consultations were begun between signatories and non-signatories (including the United States) over the possibility of modifying the Convention to allow the industrialized countries to join the Convention. The resulting 1994 Agreement on Implementation was adopted as a binding international Convention. It mandated that key articles, including those on limitation of seabed production and mandatory technology transfer, would not be applied, that the United States, if it became a member, would be guaranteed a seat on the Council of the International Seabed Authority, and finally, that voting would be done in groups, with each group able to block decisions on substantive matters. The 1994 Agreement also established a Finance Committee that would originate the financial decisions of the Authority, to which the largest donors would automatically be members and in which decisions would be made by consensus. [edit] Debate In the United States there is vigorous debate over the ratification of the treaty, with criticism coming mainly from a few anti-UN political conservatives who consider involvement in international organizations and treaties antithetical to US national interests. A small group of Republican senators, led by Jim Inhofe of Oklahoma, has blocked American ratification of the Convention, claiming that it would impinge on US sovereignty. The Bush administration, a majority of the United States Senate, and the Pentagon favor ratification, as do representatives of scientific and international legal scholars, and mining and environmentalist groups. [edit] Arguments Pro-Ratification Arguments The Environment: Oceans cover over 70 percent of the Earth. In the US, there are laws to keep marine resources available for future generations. UNCLOS sets a global standard so that all countries are legally bound to protect the marine environment, protect fish stocks, and prevent pollution with as much care as the US does. Joining UNCLOS would send a message to the world that we care about the global environment. National Security: The US military, which relies heavily on its ability to freely navigate on and fly over the sea, has been a strong advocate of UNCLOS. In the absence of treaty law, the US is forced to rely on customary law that can change as states' practices change. Also, under this customary law, the Pentagon claims that countries often make unreasonable and irresponsible claims on marine territory to obfuscate US military action. The US has tried to talk around these claims, but without a legal framework to support them, the Pentagon believes it risks compromising its intelligence and military operations at sea. International diplomacy and peaceful disput
resolution: The Convention offers a peaceful way to resolve territorial and natural resource disputes through the ISA or the Law of the Sea Tribunal, based on agreements which signatory parties have already committed to. In contrast, without ratification, the US has no peaceful recourse if another non-signatory party decides to close its straits to navigation. It helps American businesses: Each country has exclusive rights to manage the resources in areas near its coast. Under the terms of UNCLOS, which maps out the boundaries of these areas, the American zone is larger than that of any other country in the world. The size of this zone is 3.36 million square miles - bigger than the lower 48 states combined. In addition, under UNCLOS, coastal states can exercise sovereign rights over natural resources within the extended continental shelf area beyond this territory. It would also give US companies an opportunity to apply for licenses with the ISA, which manages claims to resources in the deep seabed, an area over which no country has sovereign rights. Anti-Ratification Arguments National sovereignty: The treaty creates a new UN agency with its own dispute resolution tribunal, which is not necessarily democratically elected. Should the US stop its current compliance with the US-negotiated laws of the Convention, it could be taken to the Law of the Sea Tribunal. The Environment: Some of the Convention's conservation provisions would provide new avenues for non-US environmental organizations to attempt to influence domestic US environmental policies by pursuing legal action in both US and international courts.[3] In addition, requirements that nations either harvest their entire allowable catch in certain areas or give the surplus to other nations could result in mandated overfishing.[4] Navigation rights not threatened: One of the treaty's main selling points, legally recognized navigation rights on, over, and under straits, is unnecessary because these rights are not currently threatened by law or by any military capable of opposing the US. Harm to de-militarizing operations: The treaty would for the first time require all unmanned ocean vessels, including those submarines used for mine detection to protect ships exercising the right of innocent passage, to navigate on the surface in territorial waters - effectively eliminating their value for such purposes.[5] No control over funding: The treaty gives a blank check to the UN funded by the US. The US would have no control over how the money is used. Eminent domain: The treaty applies eminent domain to intellectual property giving the UN the power to seize technology. [edit] Latest developments On May 15, 2007, President Bush announced that he had urged the Senate to ratify the UNCLOS
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Windward and leeward Windward is the direction from which the wind is blowing at the time in question. The side of a ship which is towards the windward is the weather side. If the vessel is heeling under the pressure of the wind, this will be the "higher side" Leeward is the direction downwind from the point of reference. The side of the ship towards the leeward is its lee side. If the vessel is heeling under the pressure of the wind, this will be the "lower side". Meteorological significance The terms "leeward" and "windward" refer respectively to what a game stalker would call downwind and upwind. The terms are used by seamen in relation to their ships but also in reference to islands in an archipelago and to the different sides of a single island. In the latter case, the windward side is that side of an island subject to the prevailing wind, and is thus the wetter side (see orographic precipitation). The leeward side is the side protected by the elevation of the island from the prevailing wind, and is typically the drier side of an island. Thus, leeward or windward siting is an important weather and climate factor on oceanic islands. In the case of an archipelago, "windward islands" are upwind and "leeward islands" are the downwind ones. [edit] Nautical and naval significance Main article: Sailing Windward and leeward directions are important factors to consider when sailing a sailing ship - see points of sail. Other terms with broadly the same meaning are widely used, particularly "upwind" and "downwind", and many variations using the metaphor of height ("come up", "drop down", "we're pointing higher than them" "head below that mark", and so on). The windward vessel is normally the more maneouverable vessel. For this reason, rule 12 of the International Regulations for Preventing Collisions at Sea stipulate that the leeward vessel has right of way over the windward vessel. Similarly, a square rigged warship would often try to enter battle from the windward direction (or "hold the weather gauge"), thus gaining an important tactical advantage over the opposing warship – the warship to windward could choose when to engage and when to withdraw. The opposing warship to leeward could often do little but comply without exposing itself unduly. This was particularly important once artillery was introduced to naval warfare. The ships heeled away from the wind so that the leeward vessel was exposing part of her bottom to shot. If damaged between wind and water, she was consequently in danger of sinking when on the other tack.
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