Navigation[1] is a field of study that focuses on the process of monitoring and controlling themovement of a craft orvehicle from one place to another.[2] The field of navigation includes four general categories: land navigation,[3]marine navigation,aeronautic navigation, and space navigation.[1] For marine navigation, this involves the safe movement of ships, boats and other nautical craft either on or underneath the water using positions from navigation equipment with appropriate nautical charts (electronic and paper).[4] Navigation equipment for ships is mandated under the requirements of theSOLAS Convention, depending on ship size.[5] For aeronautic (air) navigation, this involves piloting an aircraft from one geographic position to another position while monitoring the position as the flight progresses.[6] For land navigation, this involves the movement of persons, animals and vehicles from one place to another by means of navigation equipment (such as a compass or GNSS receivers), maps and visual navigation marks across urban or rural environments.[7][8]
It is also the term of art used for the specialized knowledge used bynavigators to perform navigation tasks.[4] All navigational techniques involve locating the navigator'sposition compared to known locations or patterns. Navigation, in a broader sense, can refer to any skill or study that involves the determination of position anddirection.[1] In this sense, navigation includesorienteering andpedestrian navigation.[1]
The term stems from the 1530s, fromLatinnavigationem (nom.navigatio), fromnavigatus, pp. ofnavigare "to sail, sail over, go by sea, steer a ship," fromnavis "ship" and the root ofagere "to drive".[9]
In the European medieval period, navigation was considered part of the set ofseven 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 theMarshall Islands Stick Charts of Ocean Swells. Early Pacific Polynesians used 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.[citation needed]Maritime navigation using scientific instruments such as themariner's astrolabe first occurred in the Mediterranean during the Middle Ages. Althoughland astrolabes were invented in theHellenistic period and existed inclassical antiquity and theIslamic Golden Age, the oldest record of a sea astrolabe is that ofSpanish astronomerRamon Llull dating from 1295.[10] The perfecting of this navigation instrument is attributed toPortuguese navigators during earlyPortuguese discoveries in theAge of Discovery.[11][12] The earliest known description of how to make and use a sea astrolabe comes from Spanish cosmographerMartín Cortés de Albacar'sArte de Navegar (The Art of Navigation) published in 1551,[13] based on the principle of thearchipendulum used in constructing theEgyptian pyramids.
Open-seas navigation using the astrolabe and thecompass started during the Age of Discovery in the 15th century. The Portuguese began systematically exploring theAtlantic coast ofAfrica from 1418, under the sponsorship ofPrince Henry. In 1488Bartolomeu Dias reached theIndian Ocean by this route. In 1492 theSpanish monarchs fundedChristopher Columbus's expedition to sail west to reach theIndies by crossing the Atlantic, which resulted in theDiscovery of the Americas. In 1498, a Portuguese expedition commanded byVasco da Gama reachedIndia by sailing around Africa, opening up direct trade withAsia. Soon, the Portuguese sailed further eastward, to theSpice Islands in 1512, landing inChina one year later.
The first circumnavigation of the earth was completed in 1522 with theMagellan-Elcano expedition, a Spanish voyage of discovery led by Portuguese explorerFerdinand Magellan and completed by Spanish navigatorJuan Sebastián Elcano after the former's death in thePhilippines in 1521. The fleet of seven ships sailed fromSanlúcar de Barrameda in SouthernSpain in 1519, crossed the Atlantic Ocean and after several stopovers rounded the southern tip ofSouth America. Some ships were lost, but the remaining fleet continued across thePacific making a number of discoveries includingGuam and the Philippines. By then, only two galleons were left from the original seven. TheVictoria 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. TheTrinidad sailed east from the Philippines, trying to find a maritime path back to theAmericas, but was unsuccessful. The eastward route across the Pacific, also known as thetornaviaje (return trip) was only discovered forty years later, when Spanish cosmographerAndrés de Urdaneta sailed from the Philippines, north to parallel 39°, and hit the eastwardKuroshio Current which took its galleon across the Pacific. He arrived inAcapulco on October 8, 1565.
Lines of longitude appearvertical with varying curvature in this projection, but are actually halves of great ellipses, with identical radii at a given latitude.
Lines of latitude appearhorizontal with varying curvature in this projection; but are actually circular with different radii. All locations with a given latitude are collectively referred to as acircle of latitude.
In terrestrial navigation, the location of a person, ship, plane, etc is defined as a position using a reference point/coordinates (seeCartesian coordinate system). Positions can either be referenced as latitude/longitude or a distance anddirection from a fixed reference point (bearing).[14] Lines of position can be derived from a variety of methods and equipment. By determining and monitoring positions it is possible to find and direct a person, ship, plane, etc in a scientific way from one place to another.[15] This often involves the use ofmaps orcharts from which if desired, courses can be calculated or followed depending on the projection or methods used (Rhumb line,Great circle, etc).[16]
Roughly, the latitude of a place on Earth is its angular distance north or south of theequator.[17] Latitude is usually expressed indegrees (marked with °) ranging from 0° at theEquator to 90° at the North and South poles.[17] The latitude of theNorth Pole is 90° N, and the latitude of theSouth Pole is 90° S.[17] Mariners calculated latitude in the Northern Hemisphere by sighting thepole star (Polaris) with asextant 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 a degree or so.
Similar to latitude, the longitude of a place on Earth is the angular distance east or west of theprime meridian orGreenwich meridian.[17] Longitude is usually expressed indegrees (marked with °) ranging from0° at the Greenwich meridian to180° east and west.Sydney, for example, has a longitude of about151° east.New York City has a longitude of74° west. For most of history, mariners struggled to determine longitude. Longitude can be calculated if the precise time of a sighting is known. Lacking that, one can use asextant to take alunar distance (also calledthe lunar observation, or "lunar" for short) that, with anautical almanac, can be used to calculate the time at zero longitude (seeGreenwich Mean Time).[18] Reliablemarine chronometers were unavailable until the late 18th century and not affordable until the 19th century.[19][20][21] For about a hundred years, from about 1767 until about 1850,[22] 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.[19][23]
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 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.
Mostmodern navigation relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on finding intersectinglines of position or LOP.[24]
A line of position can refer to two different things, either a line on a chart or a line between the observer and an object in real life.[25] A bearing is a measure of the direction to an object.[25] If the navigator measures the direction in real life, the angle can then be drawn on anautical chart and the navigator will be somewhere on that bearing line on the chart.[25]
In addition to bearings, navigators also often measure distances to objects.[24] On the chart, a distance produces a circle or arc of position.[24] 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.[24] Afix is the intersection of two or more LOPs.[24]
If only one line of position is available, this may be evaluated against thedead reckoning position to establish an estimated position.[26]
Lines (or circles) of position can be derived from a variety of sources:
celestial observation (a short segment of thecircle of equal altitude, but generally represented as a line),
terrestrial range (natural or man made) when two charted points are observed to be in line with each other,[27]
There are some methods seldom used today such as the maritime method of "dipping a light" to calculate the geographic range from observer to lighthouse, where the height of the lighthouse is known (from a list of lights or from a chart).[28]
Methods of navigation have changed through history.[29] Each new method has enhanced the mariner's ability to complete his voyage.[29] One of the most important judgments the navigator must make is the best method to use.[29] Some types of navigation are depicted in the table.
Illustration
Description
Application
Traditional navigation methods include:
In marine navigation,dead reckoning or DR, in which one advances a prior position using the ship's course and speed. The new position is called a DR position. It is generally accepted that only course and speed determine the DR position. Correcting the DR position forleeway, current effects, and steering error result in an estimated position or EP. Aninertial navigator develops an extremely accurate EP.[29]
Used at all times.
In marine navigation,pilotage involves navigating in restricted/coastal waters with frequent determination of position relative to geographic and hydrographic features.[29]
When within sight of land.
Land navigation is the discipline of following a route through terrain on foot or by vehicle, using maps with reference to terrain, a compass, and other basic navigational tools and/or using landmarks and signs.Wayfinding is the more basic form.
Availability has declined due to the development of accurate GNSS.
Radar navigation uses radar to determine the distance from or bearing of objects whose position is known. This process is separate from radar's use as a collision avoidance system.[29]
Primarily when within radar range of land.
Satellite navigation uses a Global Navigation Satellite System (GNSS) to determine position.[29]
Used in all situations.
The practice of navigation usually involves a combination of these different methods.[29]
By mental navigation checks, a pilot or a navigator estimates tracks, distances, and altitudes which will then help the pilot avoid gross navigation errors.[30]
Piloting (also called pilotage) involves navigating an aircraft by visual reference to landmarks,[31] or a water vessel in restricted waters and fixing its position as precisely as possible at frequent intervals.[32] More so than in other phases of navigation, proper preparation and attention to detail are important.[32] Procedures vary from vessel to vessel, and between military, commercial, and private vessels.[32] As pilotage takes place inshallow waters, it typically involves following courses to ensure sufficientunder keel clearance, ensuring a sufficient depth of water below thehull as well as a consideration forsquat.[33] It may also involve navigating a ship within a river,canal orchannel in close proximity to land.[33]
A military navigation team will nearly always consist of several people.[32] A military navigator might have bearing takers stationed at the gyro repeaters on the bridge wings for taking simultaneous bearings, while 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.[32] 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.[32] If the ship is equipped with anECDIS, it 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.[32] If apilot is aboard, as is often the case in the most restricted of waters, his judgement can generally be relied upon, further easing the workload.[32] But should the ECDIS fail, the navigator will have to rely on his skill in the manual and time-tested procedures.[32]
A celestial fix will be at the intersection of two or more circles.
Celestial navigation systems are based on observation of the positions of theSun,Moon,planets andnavigational stars using asextant or similar navigation instrument.[34] By knowing which point on the rotating Earth a celestial object is above and measuring its height above the observer's horizon, the navigator can determine his distance from that subpoint using mathematical calculation.[35] Anautical almanac and a source of time, typically amarine chronometer are used to compute the subpoint on Earth a celestial body is over, and asextant is used to measure the body's angular height above the horizon.[35] That height can then be used to compute distance from the subpoint to create a circular line of position. Alternatively sight reduction tables can be used.[36] A navigator shoots 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.[37] Since the advent of GNSS, celestial navigation is less used for marine and air navigation, though it remains useful as a backup or as another method to cross-check the accuracy of electronic systems, particularly in the open ocean.[38][39]
In order to accurately measure longitude, the precise time is required of a sextant sighting (down to the second, if possible) which is then recorded for subsequent calculation. Each second of error 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.[37] A chronometer differs from a spring-driven watch principally in that it contains a variable lever device to maintain even pressure on the mainspring, and a special balance designed to compensate for temperature variations.[37] 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.[37] The difference between GMT and chronometer time is carefully determined and applied as a correction to all chronometer readings.[37] Spring-driven chronometers must be wound at about the same time each day.[37]
Quartz crystal marine chronometers have replaced spring-driven chronometers onboard modern ships because of their greater accuracy.[37] They are maintained on GMT directly from radio time signals.[37] This eliminates chronometer error and watch error corrections.[37] Should the second hand be in error by a readable amount, it can be reset electrically.[37] The basic element for time generation is a quartz crystal oscillator.[37] The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope.[37] A calibrated adjustment capability is provided to adjust for the aging of the crystal.[37]
The chronometer is typically designed to operate for a minimum of one year on a single set of batteries.[37] Observations may be timed and ship's clocks set with a comparing watch, which is set to chronometer time and taken to the bridge wing for recording sight times.[37] In practice, a wrist watch coordinated to the nearest second with the chronometer will be adequate.[37] A stop watch, either spring wound or digital, may also be used for celestial observations.[37] 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.[37] All chronometers and watches should be checked regularly with a radio time signal.[37] Times and frequencies of radio time signals are listed in publications such asRadio Navigational Aids.[37]
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 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 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").[40] 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 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.[40]
There are three main errors that must be corrected in order to each usage for navigation.[40] The main errors are perpendicular error, side error and index error.[40] Adjustment of the sextant consists of checking and aligning all the optical elements to eliminate the overall "index error" (or index correction). Index correction should be checked, using the horizon or more preferably a star, each time the sextant is used.[40] 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.[41]
Until the widespread usage of technologies such as inertial navigation systems,VHF omnidirectional range and GNSS, air navigators used theBubble octant or bubble sextant.[42] Using this instrument to take sights, mathematical calculations could then be carried out to determine the past position of the aircraft.[43]
Inertial navigation system (INS) is adead reckoning type of navigation system that computes its position based on motion sensors.[44] Before actually navigating, 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 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 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.[45] 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 thePolaris missile program to ensure a reliable and accurate navigation system to initial its missile guidance systems. Inertial navigation systems were in wide use untilsatellite 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 but are not now widely found elsewhere.[46]
Not to be confused with satellite navigation, which depends upon satellites to function, space navigation refers to the navigation of spacecraft themselves. This has historically been achieved (during theApollo program) via anavigational 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. Navigation in space has three main components: the use of a suitable reference trajectory which describes the planned flight path of the spacecraft, monitoring the actual spacecraft position while the mission is in flight (orbit determination) and creating maneuvers to bring the spacecraft back to the reference trajectory as required (flight path control).[47]
Another possibility that has been explored for deep space navigation isPulsar 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 asNASA andESA.[48][49]
Radars can be used for navigation andmarine radars are commonly fitted to ships for navigation at sea.[50] Radar is an effective aid to navigation because it provides ranges and bearings to objects within range of the radar scanner.[51] 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.[52] A fix consisting of only radar information is called a radar fix.[53] Types of radar fixes include "range and bearing to a single object,"[54] "two or more bearings,"[54] "tangent bearings,"[54] and "two or more ranges."[54] Radar can also be used withECDIS as a means of position fixing with the radar image or distance/bearing overlaid onto anElectronic nautical chart.[51]
Parallel indexing is a technique defined by William Burger in the 1957 bookThe Radar Observer's Handbook.[55] This technique involves creating a line on the screen that is parallel to the ship's course, but offset to the left or right by some distance.[55] This parallel line allows the navigator to maintain a given distance away fromhazards.[55] 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 the ship is on or off its intended course for navigation.[56]
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.[57] Another special technique, known as the Franklin Continuous Radar Plot Technique, involves drawing the path a radar object should follow on the radar display if the ship stays on its planned course.[58] During the transit, the navigator can check that the ship is on track by checking that the pip lies on the drawn line.[58]
A radio direction finder or RDF is a device for finding the direction to aradio source. Due to radio's ability to travel very long distances "over the horizon", it makes a particularly good navigation system for ships and aircraft that might be flying at a distance from land. RDFs works by rotating a directionalantenna 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 onGermanWorld War II aircraft, as loops under the rear section of the fuselage, whereas mostUS aircraft enclosed the antenna in a small teardrop-shaped fairing.
In navigational applications, RDF signals are provided in the form ofradio beacons, the radio version of alighthouse. The signal is typically a simpleAM broadcast of amorse 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 is particularly useful due to their high power and location near major cities.
Decca,OMEGA, andLORAN-C are three similar hyperbolic navigation systems. Decca was ahyperboliclow frequencyradio navigation system (also known asmultilateration) that was first deployed duringWorld War II when the Allied forces needed a system which could be used to achieve accurate landings. As was the case withLoran 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 tooil platforms.
The OMEGA Navigation System was the first truly globalradio navigation system for aircraft, operated by theUnited 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 the North Pole to Russia. Later, it was found useful for submarines.[59] Due to the success of theGlobal 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 terrestrialnavigation system usinglow frequency radio transmitters that use 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 thelow frequency portion of the EM spectrum from 90 to 110kHz. Many nations are users of the system, including theUnited States,Japan, and several European countries. Russia uses a nearly exact system in the same frequency range, calledCHAYKA. LORAN use is in steep decline, withGPS 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.
A ship's Furuno GNSS receiver showing a GPS position
A GNSS allow smallelectronic receivers to determine their location (longitude,latitude, andaltitude) within a few meters usingtime signals transmitted along aline of sight byradio fromsatellites.[60] Positions derived can then be used with maps and charts forsatellite navigation. Since the first experimental satellite was launched in 1978, GNSS have become an indispensable aid to navigation around the world, and an important tool formap-making andland surveying. GNSS also provides a precisetime reference used in many applications including scientific study ofearthquakes, andsynchronization of telecommunications networks. Global Navigation Satellite System or GNSS is the term for satellite navigation systems that provide positioning with global coverage.[60] The first system, GPS was developed by theUnited States Department of Defense and officially named NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System). Thesatellite constellation is managed by theUnited States Air Force50th Space Wing. The cost of maintaining the system is approximatelyUS$750 million per year,[61] including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as apublic good.
With improvements in technology and developments globally, as of 2024, there are several different operational GNSS now available for navigation by the public. These include theUnited States NAVSTARGlobal Positioning System (GPS), theRussianGLONASS, theEuropean Union'sGalileo positioning system and theBeidou navigation system ofChina.[60] The different global systems have varying differences in accuracy but stated positions are normally in the range of between 1 and 10 metres accuracy depending on system and on that system's satellite coverage.[60] As a result over 100 satellites are inmedium Earth orbit, transmitting signals allowing GNSS receivers to determine the receiver'slocation, speed and direction.[60] There are also several regional GNSS systems available for navigation, including theIndian Regional Navigation Satellite System and theQuasi-Zenith Satellite System. However, not all GNSS receivers are capable of operating with these systems and older GNSS receivers, such as on old ships may not be capable of receiving all of the GNSS now available to users.[60]
Modernsmartphones act as personalGNSS navigators for civilians who own them. Overuse of these devices, whether in the vehicle or on foot, can lead to a relative inability to learn about navigated environments, resulting in sub-optimal navigation abilities when and if these devices become unavailable.[62][63][64] Typically acompass is also provided to determine direction when not moving.
Poor passage planning and deviation from the plan can lead to groundings, ship damage and cargo loss.
Passage planning or voyage planning is a procedure to develop a complete description of vessel's voyage from start to finish. The plan includes leaving the dock and harbor area, the en route portion of a voyage, approaching the destination, andmooring. According to international law, a vessel'scaptain is legally responsible for passage planning,[68] however on larger vessels, the task will be delegated to the ship'snavigator.[69]
Studies show thathuman error is a factor in 80 percent of navigational accidents and that in many cases the human making the error had access to information that could have prevented the accident.[69] The practice of voyage planning has evolved from penciling lines onnautical charts to a process ofrisk management.[69]
Passage planning consists of four stages: appraisal, planning, execution, and monitoring,[69] which are specified inInternational Maritime Organization Resolution A.893(21), Guidelines For Voyage Planning,[70] and these guidelines are reflected in the local laws of IMO signatory countries (for example, Title 33 of the U.S.Code of Federal Regulations), and a number of professional books or publications. There are some fifty elements of a comprehensive passage plan depending on the size and type of vessel.
The appraisal stage deals with the collection of information relevant to the proposed voyage as well as ascertaining risks and assessing the key features of the voyage. This will involve considering the type of navigation required e.g.Ice navigation, the region the ship will be passing through and thehydrographic information on the route. In the next stage, the written plan is created. The third stage is the execution of the finalised voyage plan, taking into account any special circumstances which may arise such as changes in the weather, which may require the plan to be reviewed or altered. The final stage of passage planning consists of monitoring the vessel's progress in relation to the plan and responding to deviations and unforeseen circumstances.
Integrated Bridge System, integrated on an Offshore Service Ship
Electronic integrated bridge concepts are driving future navigation system planning.[29] Integrated systems take inputs from various ship sensors, electronically display positioning information, and provide control signals required to maintain a vessel on a preset course.[29] The navigator becomes a system manager, choosing system presets, interpreting system output, and monitoring vessel response.[29]
Two ship's officers practicing traditional celestial navigation taking a sunsight by sextant
In traditional marine navigation, one day's work in navigation is a minimal set of tasks consistent with prudent celestial navigation. The definition and processes vary on military and civilian vessels, and from ship to ship, but the traditional method takes a form resembling:[71]
Maintain a continuous dead reckoning plot.
Take two or more star observations at morning twilight for a celestial fix (prudent to observe six stars).
Morning Sun observation. Can be taken on or nearprime vertical for longitude, or at any time for a line of position.
Determine compass error by azimuth observation of the Sun.
Computation of the interval to noon, watch time of local apparent noon, and constants for meridian or ex-meridian sights.
Noontime meridian or ex-meridian observation of the Sun for noon latitude line. Running fix or cross with Venus line for noon fix.
Noontime determination the day's run and day's set and drift.
At least one afternoon Sun line, in case the stars are not visible at twilight.
Determine compass error by azimuth observation of the Sun.
Take two or more star observations at evening twilight for a celestial fix (prudent to observe six stars).
Navigation on ships is usually always conducted on thebridge. It may also take place in adjacent space, where chart tables and publications are available. However, increasingly traditional navigation processes have been replaced with technological processes for marine navigation using GNSS and marine radar.
Navigation for cars and other land-based travel typically usesmaps,landmarks, and in recent timescomputer navigation ("satnav", short for satellite navigation), as well as any means available on water.
Submariners, divers,remotely operated underwater vehicles (ROVs) and other underwater craft carry out underwater navigation by a variety of methods and processes including GNSS, radar navigation and sonar/acoustic position fixing.[72][73]
Artificial intelligence can be utilised to assist with planning, problem-serving and decision-making processes in navigation.[74][75] This includes using AI in navigation systems such as GNSS as well as in general computing to assist with position fixing and monitoring from one position to another such as in vehicles, planes and cars.[76][77]
Professional standards for navigation depend on the type of navigation and vary by country. For marine navigation,Merchant Navydeck officers are trained and internationally certified according to theSTCW Convention.[78] Leisure and amateur mariners may undertake lessons in navigation at local/regional training schools.Naval officers receive navigation training as part of their naval training.
In land navigation, courses and training is often provided to young persons as part of general or extra-curricular education. Land navigation is also an essential part of army training. Additionally, organisations such as theScouts andDoE programme teach navigation to their students.Orienteering organisations are a type of sports that require navigational skills using a map and compass to navigate from point to point in diverse and usually unfamiliar terrain whilst moving at speed.[79]
In aviation, pilots undertakeair navigation training as part of learning to fly.
Professional organisations also assist to encourage improvements in navigation or bring together navigators in learned environments. TheRoyal Institute of Navigation (RIN) is alearned society with charitable status, aimed at furthering the development of navigation on land and sea, in the air and in space. It was founded in 1947 as a forum for mariners, pilots, engineers and academics to compare their experiences and exchange information.[80] In the US, theInstitute of Navigation (ION) is a non-profit professional organisation advancing the art and science of positioning, navigation and timing.[81]
Navigation is an essential everyday activity that involves a series of abilities that help humans and animals to locate, track, and follow paths in order to arrive at different destinations.[85][86] Navigation, inspatial cognition, allows for acquiring information about the environment by using the body andlandmarks of the environment asframes of references to createmental representations of our environment, also known as acognitive map. Humans navigate by transitioning between different spaces and coordinating bothegocentric and allocentric frames of reference.
Navigation can be distinguished into two sptial components: locomotion and wayfinding.[87] Locomotion is the process of movement from one place to another, both in humans and in animals. Locomotion helps you understand an environment by moving through a space in order to create a mental representation of it.[88]Wayfinding is defined as an active process of following or deciding upon a path between one place to another through mental representations.[89] It involves processes such as representation, planning and decision which help to avoid obstacles, to stay on course or to regulate pace when approaching particular objects.[87][90]
Navigation and wayfinding can be approached in theenvironmental space. According toDan Montello’sspace classification, there are four levels of space with the third being the environmental space. The environmental space represents a very large space, like a city, and can only be fully explored through movement since all objects and space are not directly visible.[91] AlsoBarbara Tversky systematized the space, but this time taking into consideration the three dimensions that correspond to theaxes of the human body and its extensions: above/below, front/back and left/right. Tversky ultimately proposed a fourfold classification of navigable space: space of the body, space around the body, space of navigation and space of graphics.[92]
There are two types of wayfinding in navigation: aided and unaided.[91] Aided wayfinding requires a person to use various types ofmedia, such asmaps,GPS,directional signage, etc., in their navigation process which generally involves low spatial reasoning and is less cognitively demanding. Unaided wayfinding involves no such devices for the person who is navigating.[91] Unaided wayfinding can be subdivided into ataxonomy of tasks depending on whether it is undirected or directed, which basically makes the distinction of whether there is a precise destination or not: undirected wayfinding means that a person is simplyexploring an environment for pleasure without any set destination.[93]
Directed wayfinding, instead, can be further subdivided into search vs. target approximation.[93] Search means that a person does not know where the destination is located and must find it either in an unfamiliar environment, which is labeled as an uninformed search, or in a familiar environment, labeled as an informed search. In target approximation, on the other hand, the location of the destination is known to the navigator but a further distinction is made based on whether the navigator knows how to arrive or not to the destination. Path following means that the environment, the path, and the destination are all known which means that the navigator simply follows the path they already know and arrive at the destination without much thought. For example, when you are in your city and walking on the same path as you normally take from your house to your job or university.[93] However, path finding means that the navigator knows where the destination is but does not know the route they have to take to arrive at the destination: you know where a specific store is but you do not know how to arrive there or what path to take. If the navigator does not know the environment, it is called path search which means that only the destination is known while neither the path nor the environment is: you are in a new city and need to arrive at the train station but do not know how to get there.[93] Path planning, on the other hand, means that the navigator knows both where the destination is and is familiar with the environment so they only need to plan the route or path that they should take to arrive at their target. For example, if you are in your city and need to get to a specific store that you know the destination of but do not know the specific path you need to take to get there.[93]
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