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Leading Lights
Leading lights (also known as range lights in the United States) are a pair of light beacons used in navigation to indicate a safe passage for vessels entering a shallow or dangerous channel; they may also be used for position fixing. At night, the lights are a form of leading line that can be used for safe navigation. The beacons consist of two lights that are separated in distance and elevation, so that when they are aligned, with one above the other, they provide a bearing. Range lights are often illuminated day and night. In some cases the two beacons are unlighted, in which case they are known as a range in the United States or a transit in the UK. The beacons may be artificial or natural. Operation Two lights are positioned near one another. One, called the front light, is lower than the one behind, which is called the rear light. At night when viewed from a ship, the two lights only become aligned vertically when a vessel is positioned on the correct bearing. During t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hilton Head Range Rear Light
The Rear Lighthouse of Hilton Head Range Light Station, which is also called 'Leamington Lighthouse'' is an inactive light station on Hilton Head Island in Beaufort County, South Carolina. In 1983, it was named to the National Register of Historic Places. Overview The light station was built by the U.S. Lighthouse Board in 1879 to 1880. It is a cast-iron, skeleton tower on six concrete piers. The hexagonal base is in diameter. There is a central, cylindrical stair tower with a spiral staircase. The hexagonal watch room and lantern has a wooden structure. The focal plane of the lantern is above its base and above mean sea level. The tower was covered with wooden sheathing, which was later covered with sheet metal. This sheathing has been removed. The tower originally had Hains oil lamps, which were replaced in 1893 with Funck-Heap lamps. The station was deactivated in 1932. The front range light was moveable to compensate for the shifting channel. It is no longer in existenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lighthouses
A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mark dangerous coastlines, hazardous shoals, reefs, rocks, and safe entries to harbors; they also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and has become uneconomical since the advent of much cheaper, more sophisticated and effective electronic navigational systems. History Ancient lighthouses Before the development of clearly defined ports, mariners were guided by fires built on hilltops. Since elevating the fire would improve the visibility, placing the fire on a platform became a practice that led to the development of the lighthouse. In antiquity, the lighthouse functioned more as an entrance marker to ports than as a warning signal for reefs and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Navigational Aids
Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. All navigational techniques involve locating the navigator's position compared to known locations or patterns. Navigation, in a broader sense, can refer to any skill or study that involves the determination of position and direction. In this sense, navigation includes orienteering and pedestrian navigation. History In the European medieval period, navigation was considered part of the set of '' seven mechanical arts'', none of which were used for long voyages across open ocean. Polynesian navigation is probably the earliest form of open-ocean navigation; it was b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moiré Pattern
In mathematics, physics, and art, moiré patterns ( , , ) or moiré fringes are large-scale interference patterns that can be produced when an opaque ruled pattern with transparent gaps is overlaid on another similar pattern. For the moiré interference pattern to appear, the two patterns must not be completely identical, but rather displaced, rotated, or have slightly different pitch. Moiré patterns appear in many situations. In printing, the printed pattern of dots can interfere with the image. In television and digital photography, a pattern on an object being photographed can interfere with the shape of the light sensors to generate unwanted artifacts. They are also sometimes created deliberately – in micrometers they are used to amplify the effects of very small movements. In physics, its manifestation is wave interference such as that seen in the double-slit experiment and the beat phenomenon in acoustics. Etymology The term originates from '' moire'' (''moiré' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Approach Slope Indicator
The visual approach slope indicator (VASI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during approach. These lights may be visible from up to during the day and up to or more at night. Basic visual approach slope indicators consist of one set of lights set up some from the start of the runway. Each light is designed so that it appears as either white or red, depending on the angle at which it is viewed. When the pilot is approaching the lights at the proper angle, meaning the pilot is on the glide slope, the first set of lights appears white and the second set appears red. When both sets appear white, the aircraft is too high, and when both appear red it is too low. This used to be the most common type of visual approach slope indicator system; however, it is being phased out and replaced by precision approach path indicators (PAPIs), which are closer together and therefore more efficient to sight and ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PEL Sector Light
The PEL sector light is a projector style marine beacon which is used to guide maritime vessels. It does this by projecting a colored sector out to sea with very sharp color changes as the mariner transitions from one sector to the next. Typical PEL sector lights will have a complete color change over 1 meter (sideways movement) when the mariner is 5 km from the beacon. The PEL's application becomes relevant to the mariner when combined with a local marine chart as each application of a PEL varies greatly. They are used for guiding vessels into harbor, traffic separation or to illuminate hazards. The main advantage to a PEL sector light is that it has very sharp transitions between colors (typical 0.05°) and is bright enough to be used in daylight with up to 10 Nautical Miles or 18.5 km visibility. Origin The term PEL is a generalized trademark of the Physics and Engineering Laboratory which was part of the Department of Scientific and Industrial Research (DSIR), a New ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sector Light
A sector light is a man-made pilotage and position fixing aid that consists of strictly delineated horizontal angle light beams to guide water-borne traffic through a safe channel at night in reasonable visibility. Sector lights are most often used for safe passage through shallow or dangerous waters. This may be when leaving or entering harbour. Nautical charts (paper and electronic) give all the required information. Sectors of colored glass (or plastic) are placed in the lanterns of these lights. The light will then show these colors when observed certain bearings. Bearings referring to a sector are given in degrees true, as observed from sea. Though the colors of the light will change, the characteristics will not. The change of color is not abrupt. The transition is made through an arc of uncertainty of 2° or greater. The colors that are used, are conform to the IALA Maritime Buoyage system that is designed by the International Association of Lighthouse Authorities: * whit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daymark
A daymark is a navigational aid for sailors and pilots, distinctively marked to maximize its visibility in daylight. The word is also used in a more specific, technical sense to refer to a signboard or daytime identifier that is attached to a day beacon or other aid to navigation. In that sense, a daymark conveys to the mariner during daylight hours the same significance as does the aid's light or reflector at night. Standard signboard shapes are square, triangular and rectangular; and the standard colours are red, green, orange, yellow and black. Notable daymarks * Trinity House Obelisk * Kingswear Daymark *Tasku beacon tower *Keskiniemi beacon tower *Hiidenniemi beacon tower *Laitakari beacon tower *Herring Tower, Langness *Le Hocq *La Tour Cârrée *Scharhörnbake Symbols used on US charts Chart symbols used by the US National Oceanic and Atmospheric Administration Department, 2013. See also * Landmark * Sea mark * Lighthouse A lighthouse is a tower, buildin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Själö
Själö or Nagu Själö (in Swedish) or Seili (in Finnish) is a small island (about from north to south), off the main islands of Nagu, in the Archipelago Sea, off the south west coast of Finland. Själö is part of the municipality of Pargas. The island is known for its church and nature, a research institute and a former hospital. There is another Själö in Väståboland, on the border between the former municipalities of Houtskär and Iniö. Asteroid 2292 Seili has been named after the island. History The Finnish name of the island, ''Seili'', is a corruption of the Swedish ''Själö'' ('seal island' in English, ''själ'' being the old form of ''säl'', or seal). The name indicates that the island has been a retreat for seals and an attraction for seal hunters in early times. Actually Själö, then and at least until the 18th century, comprised two islands separated by a shallow strait, which has disappeared because of the land rising from the sea, an after-effect of gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Margaree Harbour, Nova Scotia
The Municipality of the County of Inverness is a county municipality on Cape Breton Island, Nova Scotia, Canada. It provides local government to about 17,000 residents of the historical county of the same name, except for the incorporated town of Port Hawkesbury and the Whycocomagh 2 Miꞌkmaq reserve, both of which are enclaves. Public services are provided in the areas of recreation, tourism, administration, finance, and public works. History The county was named after Inverness in the Scottish Highlands from where many immigrants came. The boundaries were defined when Cape Breton Island was divided into districts in 1823. In 1996, the county was amalgamated into a single municipality with the exception of Port Hawkesbury. Coal deposits exist between Port Hastings and Cheticamp. The Inverness and Richmond Railway, from Port Hastings to Inverness, was built around 1900 to transport coal. Coal mining was unprofitable, and small scale local operations ended in 1992. The railway ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USCG
The United States Coast Guard (USCG) is the maritime security, search and rescue, and law enforcement service branch of the United States Armed Forces and one of the country's eight uniformed services. The service is a maritime, military, multi-mission service unique among the United States military branches for having a maritime law enforcement mission with jurisdiction in both domestic and international waters and a federal regulatory agency mission as part of its duties. It is the largest and most powerful coast guard in the world, rivaling the capabilities and size of most navies. The U.S. Coast Guard is a humanitarian and security service. It protects the United States' borders and economic and security interests abroad; and defends its sovereignty by safeguarding sea lines of communication and commerce across vast territorial waters spanning 95,000 miles of coastline and its Exclusive Economic Zone. With national and economic security depending upon open global trade ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
