Seamanship is the art , competence , and knowledge of operating a ship , boat or other craft on water. The Oxford Dictionary states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea."
107-598: It involves topics and development of specialised skills, including navigation and international maritime law and regulatory knowledge; weather , meteorology and forecasting; watchkeeping ; ship-handling and small boat handling; operation of deck equipment, anchors and cables; ropework and line handling; communications ; sailing ; engines ; execution of evolutions such as towing; cargo handling equipment, dangerous cargoes and cargo storage; dealing with emergencies; survival at sea and search and rescue ; and fire fighting . The degree of knowledge needed within these areas
214-432: A maritime (or marine) pilot . Marine pilots are seafarers with extensive seafaring experience and are usually qualified master mariners who have been trained as expert ship-handlers. These pilots should be conversant with all types of vessel in their local waters and possess a good knowledge of the different propulsion systems, as well as handling ships of all sizes in all weather and tidal conditions. They are also experts in
321-474: A 10.4 m (34 ft) steel cutter with two persons on board, which hove to in wind speeds averaging 80 knots for 6 hours with virtually no damage. During the ill-fated 1979 Fastnet race , of 300 yachts, 158 chose to adopt storm tactics; 86 " lay ahull ", whereby the yacht adopts a "beam on" attitude to the wind and waves; 46 ran before the wind under bare poles or trailing warps/sea anchors, and 26 hove to. 100 yachts suffered knock downs; 77 rolled (that
428-431: A boat if possible, the use of oars or sails, as well as basic sail theory, sail terminology and markings on sails. One other aspect of traditional good seamanship is housekeeping on the vessel. This involves correct stowage of stores, supplies, crew personal effects, etc. It also involves keeping the decks, engine room and accommodation clean and free of debris or spills. This reduces the chances of fire at sea and reduces
535-469: A defined initial bearing. That is, upon taking an initial bearing, one proceeds along the same bearing, without changing the direction as measured relative to true or magnetic north. Most modern navigation relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on finding intersecting lines of position or LOP. A line of position can refer to two different things, either
642-548: A degree or so. Similar to latitude, the longitude of a place on Earth is the angular distance east or west of the prime meridian or Greenwich meridian . Longitude is usually expressed in degrees (marked with °) ranging from 0° at the Greenwich meridian to 180° east and west. Sydney , for example, has a longitude of about 151° east . New York City has a longitude of 74° west . For most of history, mariners struggled to determine longitude. Longitude can be calculated if
749-478: A distance produces a circle or arc of position. Circles, arcs, and hyperbolae of positions are often referred to as lines of position. If the navigator draws two lines of position, and they intersect he must be at that position. A fix is the intersection of two or more LOPs. If only one line of position is available, this may be evaluated against the dead reckoning position to establish an estimated position. Lines (or circles) of position can be derived from
856-612: A few meters using time signals transmitted along a line of sight by radio from satellites . Receivers on the ground with a fixed position can also be used to calculate the precise time as a reference for scientific experiments. As of October 2011, only the United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS are fully globally operational GNSSs. The European Union 's Galileo positioning system
963-418: A greater degree of seamanship may be necessary for some vessel types compared to others. Seamanship involves paying close attention to the stability of the vessel at all times. This involves calculation of the vessel and the effects of its cargo at various stages of the voyage (on departure, at sea and on arrival in port) to allow for safe passage and prevent capsizing (where a vessel turns on to its side or
1070-407: A hundred years, from about 1767 until about 1850, mariners lacking a chronometer used the method of lunar distances to determine Greenwich time to find their longitude. A mariner with a chronometer could check its reading using a lunar determination of Greenwich time. In navigation, a rhumb line (or loxodrome) is a line crossing all meridians of longitude at the same angle, i.e. a path derived from
1177-402: A line on a chart or a line between the observer and an object in real life. A bearing is a measure of the direction to an object. If the navigator measures the direction in real life, the angle can then be drawn on a nautical chart and the navigator will be somewhere on that bearing line on the chart. In addition to bearings, navigators also often measure distances to objects. On the chart,
SECTION 10
#17327873202621284-450: A number of stars in succession to give a series of overlapping lines of position. Where they intersect is the celestial fix. The Moon and Sun may also be used. The Sun can also be used by itself to shoot a succession of lines of position (best done around local noon) to determine a position. In order to accurately measure longitude, the precise time of a sextant sighting (down to the second, if possible) must be recorded. Each second of error
1391-399: A particularly good navigation system for ships and aircraft that might be flying at a distance from land. RDFs works by rotating a directional antenna and listening for the direction in which the signal from a known station comes through most strongly. This sort of system was widely used in the 1930s and 1940s. RDF antennas are easy to spot on German World War II aircraft, as loops under
1498-418: A radio time signal. Times and frequencies of radio time signals are listed in publications such as Radio Navigational Aids . The second critical component of celestial navigation is to measure the angle formed at the observer's eye between the celestial body and the sensible horizon. The sextant, an optical instrument, is used to perform this function. The sextant consists of two primary assemblies. The frame
1605-529: A ship. Larger ship types usually have a crane for cargo operations and for bringing on stores, provisions and supplies for the crew. Seamanship knowledge and experience is an integral part of Dry-docking . This includes careful planning (of all jobs, tasks and repairs), adequate preparations (eg or painting), dry-docking calculations (primarily stability and upthrust), safety within the dry-dock and checks upon departure (eg plugs returned and sealed). Lifeboat, rescue boat and survival craft maintenance and operation
1712-400: A single object," "two or more bearings," "tangent bearings," and "two or more ranges." Radar can also be used with ECDIS as a means of position fixing with the radar image or distance/bearing overlaid onto an Electronic nautical chart . Parallel indexing is a technique defined by William Burger in the 1957 book The Radar Observer's Handbook . This technique involves creating a line on
1819-483: A sloop sailing along normally, either of two maneuvers will render the sailboat to be hove to. First, the jib can be literally heaved to windward, using the windward sheet and releasing the other. Then the rudder would be put across so as to turn gently towards the wind. Without the drive of the jib, and allowing time for momentum to die down, the sailboat will be unable to tack and will stop hove to. This method may be preferable when broad reaching or running before
1926-540: A stage, rigging of a bosuns ladder, canvas work, use of chain blocks and pulleys, etc. Other traditional practices apply to life onboard, such as forms of address to the Captain and in use of marine flag, including courtesies and flag signalling. Specifically, these include items such as flag signalling terms, single and double letter meanings according to the International Code of Signals, flag maintenance,
2033-411: A strong wind in a heavy sea and the prospect of tacking through the wind in order to heave to may not appeal. Bearing away from the wind so that the headsail is blanketed by the mainsail can make it easier to haul in the windward sheet. Alternatively, the vessel can simply be turned normally to tack through the wind, without freeing the jibsheet. The mainsail should self-tack onto the other side, but
2140-404: A sufficient depth of water below the hull as well as a consideration for squat . It may also involve navigating a ship within a river, canal or channel in close proximity to land. A military navigation team will nearly always consist of several people. A military navigator might have bearing takers stationed at the gyro repeaters on the bridge wings for taking simultaneous bearings, while
2247-413: A variety of sources: There are some methods seldom used today such as "dipping a light" to calculate the geographic range from observer to lighthouse. Methods of navigation have changed through history. Each new method has enhanced the mariner's ability to complete his voyage. One of the most important judgments the navigator must make is the best method to use. Some types of navigation are depicted in
SECTION 20
#17327873202622354-453: Is Pulsar navigation , which compares the X-ray bursts from a collection of known pulsars in order to determine the position of a spacecraft. This method has been tested by multiple space agencies, such as NASA and ESA . A radio direction finder or RDF is a device for finding the direction to a radio source. Due to radio's ability to travel very long distances "over the horizon", it makes
2461-427: Is a next generation GNSS in the final deployment phase, and became operational in 2016. China has indicated it may expand its regional Beidou navigation system into a global system. Heaving to In sailing , heaving to (to heave to and to be hove to ) is a way of slowing a sailing vessel's forward progress, as well as fixing the helm and sail positions so that the vessel does not have to be steered. It
2568-436: Is a quartz crystal oscillator. The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope. A calibrated adjustment capability is provided to adjust for the aging of the crystal. The chronometer is designed to operate for a minimum of one year on a single set of batteries. Observations may be timed and ship's clocks set with a comparing watch, which is set to chronometer time and taken to
2675-425: Is a rigid triangular structure with a pivot at the top and a graduated segment of a circle, referred to as the "arc", at the bottom. The second component is the index arm, which is attached to the pivot at the top of the frame. At the bottom is an endless vernier which clamps into teeth on the bottom of the "arc". The optical system consists of two mirrors and, generally, a low power telescope. One mirror, referred to as
2782-568: Is a statutory requirement and considered good seamanship to regularly practice (drill) these skills when at sea. Other emergency skills include the Man overboard rescue turn . Historic or traditional seamanship skills are less frequently used on modern commercial ships, but are usually still practiced in training colleges and used on smaller ships, fishing vessels and leisure craft. These include ropework (included tying knots, rope splicing , wire splicing, lashings and whippings ), as well as rigging of
2889-434: 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. In
2996-429: Is an essential part of seamanship. This involves being able to operate survival craft in emergencies, but also to be able to maintain them effectively to operate in accordance with SOLAS requirements. The STCW Convention requires that modern seafarers be familiar with emergency operations, including fire fighting. Personnel at sea are required to undertake fire fighting training at shore based training establishments. It
3103-403: Is based on the nautical mile . Navigation also includes electronics such as GPS and Loran (Long Range Navigation). Celestial navigation involves taking sights by sextant on the planets, moon, stars, sun and using the data with a nautical almanac and sight reduction tables to determine positions. Accurate time information is also needed. After nautical dusk , navigation at sea referencing
3210-521: Is being able to manoeuvre a vessel safely with accuracy and precision both at sea and also in port and during pilotage . Unlike land based vehicles, a ship afloat is subject to the forces of the water in which it floats, as well as the resistance and effects of marine weather. A complicating factor is that the mass of a ship that has to be accounted for when stopping and starting, as the inertia of large vessels may take large distances to stop and therefore ship-handlers must be aware of basic Hydrodynamics and
3317-423: Is commonly used for a "break"; this may be to wait for the tide before proceeding, or to wait out a strong or contrary wind. For a solo or shorthanded sailor it can provide time to go below deck, to attend to issues elsewhere on the boat or to take a meal break. Heaving to can make reefing a lot easier, especially in traditional vessels with several sails. It is also used as a storm tactic. A sailing vessel that
Seamanship - Misplaced Pages Continue
3424-1053: Is considered to be the V-2 guidance system deployed by the Germans in 1942. However, inertial sensors are traced to the early 19th century. The advantages INSs led their use in aircraft, missiles, surface ships and submarines. For example, the U.S. Navy developed the Ships Inertial Navigation System (SINS) during the Polaris missile program to ensure a reliable and accurate navigation system to initial its missile guidance systems. Inertial navigation systems were in wide use until satellite navigation systems (GPS) became available. INSs are still in common use on submarines (since GPS reception or other fix sources are not possible while submerged) and long-range missiles. Not to be confused with satellite navigation, which depends upon satellites to function, space navigation refers to
3531-460: Is dependent upon the nature of the work and the type of vessel employed by a seafarer . Seamanship on a commercial level involves a knowledge of all the different ship types (such as bulk carriers , container ships , oil tankers , cruise ships , platform supply vessels , and others), including a basic knowledge of ship recognition, a basic understanding of nautical terms, ship structure and naval architecture and cargo operations, specific to
3638-441: Is equivalent to 15 seconds of longitude error, which at the equator is a position error of .25 of a nautical mile, about the accuracy limit of manual celestial navigation. The spring-driven marine chronometer is a precision timepiece used aboard ship to provide accurate time for celestial observations. A chronometer differs from a spring-driven watch principally in that it contains a variable lever device to maintain even pressure on
3745-409: Is hove to is still, for the purposes of the collision regulations , on a defined tack. Therefore, unless other considerations dictate differently, it is helpful to heave to on the starboard tack, in order to be a "stand-on vessel", as per the regulations. The term is also used in the context of vessels under power and refers to bringing the vessel to a complete stop. For example, in waters over which
3852-519: Is important because when a pilot is in command, the master can not take any action, but is limited to advising the pilot on any circumstance that creates what he considers a dangerous situation. A working knowledge of the relevant rules and regulations, including those of the International Maritime Organization is good seamanship as it ensures compliance with international, flag and port State requirements. For example,
3959-470: Is important when choosing the tack, heaving to, and remaining hove to, in a confined space that adequate room is allowed for these maneuvers. Heaving to has been used by a number of yachts to survive storm conditions (winds greater than Force 10 , 48–55 knots, 89–102 km/h, 55–63 mph). During the June 1994 Queen's Birthday Storm, all yachts that hove to survived the storm. This included Sabre ,
4066-503: Is little or no specialisation. Deck crew perform all boat handling functions. The officers of the ship are responsible for navigation, communication, and watch supervision. Navigation 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. The field of navigation includes four general categories: land navigation, marine navigation , aeronautic navigation, and space navigation. It
4173-478: Is not affected by adverse weather conditions and it cannot be detected or jammed. Its disadvantage is that since the current position is calculated solely from previous positions and motion sensors, its errors are cumulative, increasing at a rate roughly proportional to the time since the initial position was input. Inertial navigation systems must therefore be frequently corrected with a location 'fix' from some other type of navigation system. The first inertial system
4280-443: Is only the jib and the mainsail . A cutter may have more than one headsail, and a ketch , yawl or schooner may have more than one sail on a boom . In what follows, the jibs and boomed sails on such craft can either be treated as one of each, or lowered for the purposes of reduced windage, heel or complexity when heaving to for any length of time. When a sloop is hove to, the jib is backed. This means that its windward sheet
4387-453: Is particularly useful due to their high power and location near major cities. Decca , OMEGA , and LORAN-C are three similar hyperbolic navigation systems. Decca was a hyperbolic low frequency radio navigation system (also known as multilateration ) that was first deployed during World War II when the Allied forces needed a system which could be used to achieve accurate landings. As
Seamanship - Misplaced Pages Continue
4494-459: Is reasonable for the navigator to simply monitor the progress of the ship along the chosen track, visually ensuring that the ship is proceeding as desired, checking the compass, sounder and other indicators only occasionally. If a pilot is aboard, as is often the case in the most restricted of waters, his judgement can generally be relied upon, further easing the workload. But should the ECDIS fail,
4601-447: Is the art and science of safely and efficiently directing the movements of a vessel from one point to another. Piloting uses water depth and visible references, while dead reckoning uses courses and distances from the last known position. More than just finding a vessel's present location, safe navigation includes predicting future location, route planning and collision avoidance. Nautical navigation in western nations, like air navigation ,
4708-406: Is tight holding the sail to windward. The mainsail sheet is often eased, or the mainsail reefed , to reduce forward movement, or "fore-reaching". The rudder is placed so that, should the boat make any forward movement, it will be turned into the wind, so as to prevent forward momentum building up. In a centerboard boat the centerboard will be partially raised and the tiller held down hard. For
4815-773: Is upside down). This includes familiarity and application of the Load Line Convention , where a vessel can only be safely loaded to its markings to ensure residual stability for the likely weather conditions. Seafarers should regularly inspect their vessel and ensure the hull is in good condition for navigation. Seamanship skills apply to the safe use of different types of lifting gear, whether for cargo operations or for bringing on stores, supplies and provisions. These example Derricks , Union purchase arrangements, midship or aft cranes , heavy lifting gear, rigging other sheer legs etc. This should include knowledge of calculations of stresses and effects on stability. Navigation
4922-499: The International Regulations for Preventing Collisions at Sea are the principal international rules for navigation between vessels at sea. Rule 2 sets out responsibility for safe navigation by stating “Nothing in these Rules shall exonerate any vessel or the owner, master or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution, which may be required by
5029-909: The Spanish monarchs funded Christopher Columbus 's expedition to sail west to reach the Indies by crossing the Atlantic, which resulted in the Discovery of the Americas . In 1498, a Portuguese expedition commanded by Vasco da Gama reached India by sailing around Africa, opening up direct trade with Asia . Soon, the Portuguese sailed further eastward, to the Spice Islands in 1512, landing in China one year later. The first circumnavigation of
5136-498: The Suez canal . Crew should be able to keep the vessel from collisions, moor the vessel during canal lockgate operations and also respond to local currents and river conditions while on passage. Two other types of operations, berthing alongside another ship (usually for Ship-to-ship cargo transfer and replenishment at sea, are occasionally included in ship-handling seamanship for some vessel types. In addition to being fully conversant with
5243-703: The United Kingdom and the United States of America ), the pilot's role is as an advisor. However, in practice, they are likely to have the conduct of the vessel, especially on larger ships using tug boats to assist. In some places, specifically in the Panama Canal , a pilot assumes command of a vessel and is not classed as "an advisor". Other instances may be crossing the sill of a drydock , or in any port in Russia (or ex-Soviet States). This distinction
5350-490: The United States in cooperation with six partner nations. OMEGA was developed by the United States Navy for military aviation users. It was approved for development in 1968 and promised a true worldwide oceanic coverage capability with only eight transmitters and the ability to achieve a four-mile (6 km) accuracy when fixing a position. Initially, the system was to be used for navigating nuclear bombers across
5457-416: The charted area , including the depth of water in which their ship is navigating. Ship-handling in coastal areas may involve arriving and departing a berth, anchorage or buoy , maneuvering in confined channels and harbours and in proximity to other ships, whilst at all times navigating safely. Seamanship also involves safe navigation in restricted waterways, for example in river and canal transits eg along
SECTION 50
#17327873202625564-400: The "index mirror" is fixed to the top of the index arm, over the pivot. As the index arm is moved, this mirror rotates, and the graduated scale on the arc indicates the measured angle ("altitude"). The second mirror, referred to as the "horizon glass", is fixed to the front of the frame. One half of the horizon glass is silvered and the other half is clear. Light from the celestial body strikes
5671-456: The 1530s, from Latin navigationem (nom. navigatio ), from navigatus , pp. of navigare "to sail, sail over, go by sea, steer a ship," from navis "ship" and the root of agere "to drive". Roughly, the latitude of a place on Earth is its angular distance north or south of the equator . Latitude is usually expressed in degrees (marked with °) ranging from 0° at the Equator to 90° at
5778-543: 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 based on memory and observation recorded on scientific instruments like the Marshall Islands Stick Charts of Ocean Swells . Early Pacific Polynesians used
5885-553: The North Pole to Russia. Later, it was found useful for submarines. Due to the success of the Global Positioning System the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was terminated on September 30, 1997, and all stations ceased operation. LORAN is a terrestrial navigation system using low frequency radio transmitters that use
5992-651: The North and South poles. The latitude of the North Pole is 90° N, and the latitude of the South Pole is 90° S. Mariners calculated latitude in the Northern Hemisphere by sighting the pole star ( Polaris ) with a sextant and using sight reduction tables to correct for height of eye and atmospheric refraction. The height of Polaris in degrees above the horizon is the latitude of the observer, within
6099-690: The Philippines, trying to find a maritime path back to the Americas , but was unsuccessful. The eastward route across the Pacific, also known as the tornaviaje (return trip) was only discovered forty years later, when Spanish cosmographer Andrés de Urdaneta sailed from the Philippines, north to parallel 39°, and hit the eastward Kuroshio Current which took its galleon across the Pacific. He arrived in Acapulco on October 8, 1565. The term stems from
6206-575: The U.S., the progression begins with what is known as "the six pack", a license that allows fishing guides to operate with up to six passengers . In the United Kingdom , all seafarers, both deck officers and crew, must complete an Efficient Deck Hand (EDH Course) at an approved training provider under direction of the UK Merchant Navy Training Board . The crew of a large ship will typically be organized into "divisions" or "departments", each with its own specialty. For example,
6313-527: The United States has jurisdiction the Coast Guard may, under 14 U.S.C. §522 , demand that a boat "heave to" in order to enforce federal laws. A sailing vessel is "hove to" when it is at or nearly at rest because the driving action from one or more sails is approximately balanced by the drive from the other(s). This always involves "backing" one or more sails, so that the wind is pressing against
6420-495: The bridge wing for recording sight times. In practice, a wrist watch coordinated to the nearest second with the chronometer will be adequate. A stop watch, either spring wound or digital, may also be used for celestial observations. In this case, the watch is started at a known GMT by chronometer, and the elapsed time of each sight added to this to obtain GMT of the sight. All chronometers and watches should be checked regularly with
6527-414: The casualty. Finally, in either case, the tiller or wheel should be lashed so that the rudder cannot move again, and the mainsheet adjusted so that the boat lies with the wind ahead of the beam with minimal speed forward. Usually this involves easing the sheet slightly compared to a closehauled position, but depending on the relative sizes of the sails, the shape and configuration of the keel and rudder and
SECTION 60
#17327873202626634-496: The change of injury eg due to slips, trips and falls. Officers and Masters must pass formal examinations to demonstrate their knowledge at various levels, in accordance with national laws and the STCW Convention . These examinations have a progression based on the size and complexity of the ship, including its sailing area as well as by rank. Globally, most seafarers are required to possess a basic seamanship certificate. In
6741-421: The civilian navigator on a merchant ship or leisure craft must often take and plot their position themselves, typically with the aid of electronic position fixing. While the military navigator will have a bearing book and someone to record entries for each fix, the civilian navigator will simply pilot the bearings on the chart as they are taken and not record them at all. If the ship is equipped with an ECDIS , it
6848-462: The deck department is responsible for navigation, ship handling and general maintenance, while the engineering division are responsible for propulsion and other mechanical systems. Crew start on the most basic duties and as they gain experience and expertise advance within their area. Crew who have gained proficiency become "able seamen", "petty officers", "rated", or "mates" depending on the ship type and organisation. On smaller commercial craft, there
6955-666: The earth was completed in 1522 with the Magellan-Elcano expedition , a Spanish voyage of discovery led by Portuguese explorer Ferdinand Magellan and completed by Spanish navigator Juan Sebastián Elcano after the former's death in the Philippines in 1521. The fleet of seven ships sailed from Sanlúcar de Barrameda in Southern Spain in 1519, crossed the Atlantic Ocean and after several stopovers rounded
7062-725: The first opportunity. Training is more formal in the merchant navy and naval forces, but still covers the basics of traditional seamanship. Smaller vessel types may have traditional methods of seamanships unique to their vessel types, for example turtling on dinghies and small sailing boats. Boatwork is a traditional seamanship skill. On commercial ships, this is usually limited to rescue boats and lifeboats, however yachts and other vessels such as passenger ships may have tenders and small boats for transporting people between ship/shore. boatwork includes knowledge and operation of different types of boat, launching procedures, recovery of boats (in normal and in heavy weather conditions), how to beach
7169-421: The forward side of the cloth, rather than the aft side as it normally would for the sail to drive the vessel forwards. On a square rigged vessel with more than one mast, a number of options are available; these generally involve bracing round the square topsail on one or more masts to an aback position to counterbalance the sails that remain set in their normal position. On a modern two-sailed sloop , there
7276-431: The geographical areas they work. In most countries, the pilot takes over the 'conduct' of the navigation from the ship master. This means that the master and crew should adhere to the pilot's orders in respect of the safe navigation of the vessel when in a compulsory pilotage area. However, the master may with good cause resume 'conduct' of the vessel's navigation but this is not done lightly. In some countries and areas (eg
7383-418: The horizon is no longer possible, and after nautical dawn such navigation again becomes possible. Ice navigation involves navigating and operating a ship within sea ice conditions. Along with general navigation, seamanship involves being able to respond to weather at sea. For example, the onset of heavy or rough weather may require an alternative passage plan (or weather routeing) for the ship, as well as
7490-426: The horizon or more preferably a star, each time the sextant is used. The practice of taking celestial observations from the deck of a rolling ship, often through cloud cover and with a hazy horizon, is by far the most challenging part of celestial navigation. Inertial navigation system (INS) is a dead reckoning type of navigation system that computes its position based on motion sensors. Before actually navigating,
7597-480: The index mirror and is reflected to the silvered portion of the horizon glass, then back to the observer's eye through the telescope. The observer manipulates the index arm so the reflected image of the body in the horizon glass is just resting on the visual horizon, seen through the clear side of the horizon glass. Adjustment of the sextant consists of checking and aligning all the optical elements to eliminate "index correction". Index correction should be checked, using
7704-669: The initial latitude and longitude and the INS's physical orientation relative to the Earth (e.g., north and level) are established. After alignment, an INS receives impulses from motion detectors that measure (a) the acceleration along three axes (accelerometers), and (b) rate of rotation about three orthogonal axes (gyroscopes). These enable an INS to continually and accurately calculate its current latitude and longitude (and often velocity). Advantages over other navigation systems are that, once aligned, an INS does not require outside information. An INS
7811-463: The jib is held aback. Finally the rudder is put the other way, as if trying to tack back again. Without the drive of the jib, she cannot do this and will stop hove to. This method is fast to implement and is recommended by sail training bodies such as the RYA as a "quick stop" reaction to a man overboard emergency, for sailing boats that have an engine available for further maneuvers to approach and pick up
7918-448: The mainspring, and a special balance designed to compensate for temperature variations. A spring-driven chronometer is set approximately to Greenwich mean time (GMT) and is not reset until the instrument is overhauled and cleaned, usually at three-year intervals. The difference between GMT and chronometer time is carefully determined and applied as a correction to all chronometer readings. Spring-driven chronometers must be wound at about
8025-667: The motion of stars, weather, the position of certain wildlife species, or the size of waves to find the path from one island to another. Maritime navigation using scientific instruments such as the mariner's astrolabe first occurred in the Mediterranean during the Middle Ages. Although land astrolabes were invented in the Hellenistic period and existed in classical antiquity and the Islamic Golden Age ,
8132-544: The navigation of spacecraft themselves. This has historically been achieved (during the Apollo program ) via a navigational computer , an Inertial navigation system, and via celestial inputs entered by astronauts which were recorded by sextant and telescope. Space rated navigational computers, like those found on Apollo and later missions, are designed to be hardened against possible data corruption from radiation. Another possibility that has been explored for deep space navigation
8239-462: The navigator will have to rely on his skill in the manual and time-tested procedures. Celestial navigation systems are based on observation of the positions of the Sun , Moon , planets and navigational stars . Such systems are in use as well for terrestrial navigating as for interstellar navigating. By knowing which point on the rotating Earth a celestial object is above and measuring its height above
8346-484: The nozzle are the ship can be steered astern which a conventional rudder cannot, and the ship can be steered fully under control to a standstill switching between ahead and astern mode to give complete control over speed. Seamanship applies to general Mooring practices and anchoring (anchors are a device used to secure a vessel to the bed of a body of water to prevent the craft from drifting) and established marine procedures for anchoring (anchorwork). This also includes
8453-405: The observer's horizon, the navigator can determine his distance from that subpoint. A nautical almanac and a marine chronometer are used to compute the subpoint on Earth a celestial body is over, and a sextant is used to measure the body's angular height above the horizon. That height can then be used to compute distance from the subpoint to create a circular line of position. A navigator shoots
8560-506: The oldest record of a sea astrolabe is that of Spanish astronomer Ramon Llull dating from 1295. The perfecting of this navigation instrument is attributed to Portuguese navigators during early Portuguese discoveries in the Age of Discovery . The earliest known description of how to make and use a sea astrolabe comes from Spanish cosmographer Martín Cortés de Albacar 's Arte de Navegar ( The Art of Navigation ) published in 1551, based on
8667-479: The ordinary practice of seamen, or by the special circumstances of the case.” The ordinary practice of seaman is seen as equivalent wording for seamanship. Other accepted practices of seamanship relating to the COLREGs include maintaining a proper look-out (Rule 5), proceeding at a safe speed (Rule 6) and taking correct actions to avoid collision (Rule 8). Seamanship involves the correct and adequate maintenance of
8774-476: The path a radar object should follow on the radar display if the ship stays on its planned course. During the transit, the navigator can check that the ship is on track by checking that the pip lies on the drawn line. Global Navigation Satellite System or GNSS is the term for satellite navigation systems that provide positioning with global coverage. A GNSS allow small electronic receivers to determine their location ( longitude , latitude , and altitude ) within
8881-443: The pitch and not the direction of rotation was reversed to go astern. These propellers rotate counterclockwise at all times and so the "walk" is "normal". Other variations on propulsion include what are known as bucket rudders and Kort Nozzles where instead of a conventional rudder a pair of dish-shaped rudders, one either side of the propeller can be swivelled vertically to direct the propeller thrust through 360 degrees. Thus to put
8988-412: The precise time of a sighting is known. Lacking that, one can use a sextant to take a lunar distance (also called the lunar observation , or "lunar" for short) that, with a nautical almanac , can be used to calculate the time at zero longitude (see Greenwich Mean Time ). Reliable marine chronometers were unavailable until the late 18th century and not affordable until the 19th century. For about
9095-626: The principle of the archipendulum used in constructing the Egyptian pyramids . Open-seas navigation using the astrolabe and the compass started during the Age of Discovery in the 15th century. The Portuguese began systematically exploring the Atlantic coast of Africa from 1418, under the sponsorship of Prince Henry . In 1488 Bartolomeu Dias reached the Indian Ocean by this route. In 1492
9202-445: The principles of ship-handling, a good shiphandler or pilot will have developed their sense of 'situational awareness' to a point well beyond that of an ordinary member of a ship's crew; their reactions will appear to be instinctive, positive and at all times safe. A key ability for a ship-handler with good seamanship is to possess an understanding of how wind , tide and swell influence vessel movement, along with passing vessels and
9309-410: The propeller would turn counterclockwise when going astern and the stern would walk to port. This aided in docking operations, where "port side to" was the preferred situation and the vessel would be brought to the dock with a small bow-in angle and backing would flatten the angle, slow or stop the vessel and walk it alongside. An exception to this is vessels which use a controllable-pitch propeller, where
9416-429: The radar scanner. When a vessel (ship or boat) is within radar range of land or fixed objects (such as special radar aids to navigation and navigation marks) the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a chart. A fix consisting of only radar information is called a radar fix. Types of radar fixes include "range and bearing to
9523-517: The rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing. In navigational applications, RDF signals are provided in the form of radio beacons , the radio version of a lighthouse . The signal is typically a simple AM broadcast of a morse code series of letters, which the RDF can tune in to see if the beacon is "on the air". Most modern detectors can also tune in any commercial radio stations, which
9630-409: The same frequency range, called CHAYKA . LORAN use is in steep decline, with GPS being the primary replacement. However, there are attempts to enhance and re-popularize LORAN. LORAN signals are less susceptible to interference and can penetrate better into foliage and buildings than GPS signals. Radar is an effective aid to navigation because it provides ranges and bearings to objects within range of
9737-412: The same time each day. Quartz crystal marine chronometers have replaced spring-driven chronometers aboard many ships because of their greater accuracy. They are maintained on GMT directly from radio time signals. This eliminates chronometer error and watch error corrections. Should the second hand be in error by a readable amount, it can be reset electrically. The basic element for time generation
9844-400: The screen that is parallel to the ship's course, but offset to the left or right by some distance. This parallel line allows the navigator to maintain a given distance away from hazards . The line on the radar screen is set to a specific distance and angle, then the ship's position relative to the parallel line is observed. This can provide an immediate reference to the navigator as to whether
9951-409: The shape of the nearby seabed (the interaction effect). These must also be combined with an understanding of a specific vessel's performance, including its propulsion and stopping distance to allow safe handling. Fundamental to low-speed maneuvering of most vessel types is an understanding of the configuration and handedness of the propeller (s). An effect known as propeller walk will kick the stern of
10058-511: The ship is on or off its intended course for navigation. Other techniques that are less used in general navigation have been developed for special situations. One, known as the "contour method," involves marking a transparent plastic template on the radar screen and moving it to the chart to fix a position. Another special technique, known as the Franklin Continuous Radar Plot Technique, involves drawing
10165-482: The ship’s structure and equipment to keep the vessel seaworthy . This involves knowledge of tasks such as painting, greasing, renewing ropes, wires and other equipment items. Seamanship also involves a working knowledge of the relevant wires, ropes, chains, shackles and slings onboard. This includes mooring ropes using to keep the vessel secure in port. Seamanship on some vessel types may involves being able to maintain and use marine cranes and lifting equipment if fitted on
10272-609: The southern tip of South America . Some ships were lost, but the remaining fleet continued across the Pacific making a number of discoveries including Guam and the Philippines. By then, only two galleons were left from the original seven. The Victoria led by Elcano sailed across the Indian Ocean and north along the coast of Africa, to finally arrive in Spain in 1522, three years after its departure. The Trinidad sailed east from
10379-402: The state of the wind and sea, each skipper will have to experiment. After this the boat can be left indefinitely, only keeping a lookout for other approaching vessels. When hove to, the boat will heel, there will be some drift to leeward and some tendency to forereach, so adequate seaway must be allowed for. In rough weather, this leeway can actually leave a "slick" effect to windward, in which
10486-809: The table. The practice of navigation usually involves a combination of these different methods. By mental navigation checks, a pilot or a navigator estimates tracks, distances, and altitudes which will then help the pilot avoid gross navigation errors. Piloting (also called pilotage) involves navigating an aircraft by visual reference to landmarks, or a water vessel in restricted waters and fixing its position as precisely as possible at frequent intervals. More so than in other phases of navigation, proper preparation and attention to detail are important. Procedures vary from vessel to vessel, and between military, commercial, and private vessels. As pilotage takes place in shallow waters , it typically involves following courses to ensure sufficient under keel clearance , ensuring
10593-462: The time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. The current version of LORAN in common use is LORAN-C, which operates in the low frequency portion of the EM spectrum from 90 to 110 kHz . Many nations are users of the system, including the United States , Japan , and several European countries. Russia uses a nearly exact system in
10700-557: The use of drogues as applicable. Anchor work includes an understanding and awareness of types of anchors, marks on anchors and cable and shackles. It includes learning established procedures for securing anchors and cable, use of windlasses, how to prepare the anchors/clearing away anchors for letting go, letting-go (dropping) the anchor, keeping an anchor watch, clearing a foul Hawse , weighing anchor and securing anchors for sea. Most commercial vessels in excess of size limits determined by local authorities are handled in confined areas by
10807-755: The use of an alternative heading to keep the vessel from rolling ( Heaving to ). Additionally, heavy weather precautions onboard such as lashing furniture in the accommodation or keeping crew off the deck is considered good seamanship when navigating in heavy weather. Navigation and seamanship also involves a working knowledge of correct marine communications and the Global Maritime Distress and Safety System . Seamanship also involves recognition of and navigation with Buoys including IALA maritime buoyage such as Lateral marks , Cardinal marks , Safe water marks , Special marks and Isolated danger marks . A fundamental skill of professional seamanship
10914-403: The use of ensigns and also Morse code procedure and practice. In the days of sailing ships , an able seaman was expected to be able to "hand, and reef, and steer" and to "know the ropes" , the basic knowledge on the identity of the many ropes with different functions. This latter knowledge was essential for both safety and efficient working - those without it would be dismissed or dis-rated at
11021-462: The vessel into astern mode the rudder can be rotated through 180 degrees without altering the speed and direction of the engine. Since with the conventional propeller or rudder configuration the propeller is designed to operate at maximum efficiency when going ahead, it produces far less thrust when going astern. But with the Kort Nozzle, the ahead and astern thrust is the same. Other advantages of
11128-417: The vessel the seafarer is working on. Some ship types will have specialist cargo equipment and tools; for example, a bulk carrier may have gantry cranes or grabs for cargo or a container ship may have container lashings. Cargoes should be properly stowed and secured to prevent shifting while at sea. Oil tankers and gas carriers can be somewhat complex due to the hazardous nature of their cargoes, and therefore
11235-399: The vessel to port or starboard depending on the configuration and the type of propeller, when large variations on propeller rotation speed or changes of propeller rotation direction take place. (In single-screw vessels where the rotation of the propeller is reversed on an astern bell, a standard was established that the propeller would turn clockwise when viewed from astern. This would mean that
11342-403: The waves are smaller than elsewhere. This can make a rest or meal break a little more comfortable at times. To come out from the hove-to position and get under way again, the tiller or wheel is unlashed and the windward jibsheet is released, hauling in the normal leeward one. Bearing off the wind using the rudder will get the boat moving and then she can be maneuvered onto any desired course. It
11449-495: Was the case with Loran C , its primary use was for ship navigation in coastal waters. Fishing vessels were major post-war users, but it was also used on aircraft, including a very early (1949) application of moving-map displays. The system was deployed in the North Sea and was used by helicopters operating to oil platforms . The OMEGA Navigation System was the first truly global radio navigation system for aircraft, operated by
#261738