Editing Navigation (section)

==Methods of navigation==
Most [[Navigation system|modern navigation]] relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on finding intersecting [[line of position|lines of position]] or LOP.<ref name="mal615">Maloney, 2003:615.</ref>

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.<ref name="mal614">Maloney, 2003:614</ref> A bearing is a measure of the direction to an object.<ref name="mal614"/> 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.<ref name="mal614"/>

In addition to bearings, navigators also often measure distances to objects.<ref name="mal615"/> On the chart, a distance produces a circle or arc of position.<ref name="mal615"/> 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.<ref name="mal615"/> A [[fix (position)|fix]] is the intersection of two or more LOPs.<ref name="mal615"/>

If only one line of position is available, this may be evaluated against the [[dead reckoning]] position to establish an estimated position.<ref name="mal618">Maloney, 2003:618.</ref>

Lines (or circles) of position can be derived from a variety of sources:
* celestial observation (a short segment of the [[circle 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,<ref name="mal622">Maloney, 2003:622.</ref>
* compass bearing to a charted object,
* radar range to a charted object,
* on certain coastlines, a depth sounding from [[Fathometer|echo sounder]] or hand [[Sounding line|lead line]].

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).<ref name="q471">{{cite book | last=Rousmaniere | first=John | title=The Annapolis Book of Seamanship: Third Edition | publisher=Simon and Schuster | publication-place=New York | date=1999 | isbn=978-0-684-85420-5 | page=214-215}}</ref>

Methods of navigation have changed through history.<ref name="bow1">Bowditch, 2002:1.</ref> Each new method has enhanced the mariner's ability to complete his voyage.<ref name="bow1"/> One of the most important judgments the navigator must make is the best method to use.<ref name="bow1"/> Some types of navigation are depicted in the table.

{| class="wikitable" style="font-size:95%"
|-
! Illustration !! Description !! Application
|- valign="top"
! colspan="3" | Traditional navigation methods include:
|- valign="top"
|[[File:Cruising sailor navigating.jpg|100px]]
|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 for [[leeway]], current effects, and steering error result in an estimated position or EP. An [[Inertial guidance system|inertial navigator]] develops an extremely accurate EP.<ref name="bow1"/>
|Used at all times.
|-valign="top"
|[[File:SplitPointLighthouse.jpg|100px]]
|In marine navigation, [[pilotage]] involves navigating in restricted/coastal waters with frequent determination of position relative to geographic and hydrographic features.<ref name="bow1"/>
|When within sight of land.
|-valign="top"
|[[File:Orienteering map.jpg|100px]]
|[[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.
|Used at all times.
|-valign="top"
|[[File:Moon-Mdf-2005.jpg|100px]]
|[[Celestial navigation]] involves reducing celestial measurements to lines of position using tables, [[spherical trigonometry]], and [[Nautical almanac|almanacs]]. It is primarily used at sea but can also be used on land.
|Used primarily as a backup to [[satellite navigation|satellite]] and other [[Radio navigation|electronic systems]] in the open ocean.<ref name="bow1"/>
|-valign="top"
! colspan="3" | [[Electronic navigation]] covers any method of [[position fixing]] using electronic means, including:
|-valign="top"
|[[File:Decca Navigator Mk 12.jpg|100px]]
|[[Radio navigation]] uses radio waves to determine position by either [[radio direction finder|radio direction finding systems]] or hyperbolic systems, such as [[Decca Navigator System|Decca]], [[OMEGA Navigation System|Omega]] and [[LORAN-C]].
| Availability has declined due to the development of accurate GNSS.
|-valign="top"
|[[File:Radar screen.JPG|100px]]
|[[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.<ref name="bow1"/>
| Primarily when within radar range of land.
|-valign="top"
|[[File:GPS Satellite NASA art-iif.jpg|100px]]
|[[Satellite navigation]] uses a Global Navigation Satellite System (GNSS) to determine position.<ref name="bow1"/>
|Used in all situations.
|}

The practice of navigation usually involves a combination of these different methods.<ref name="bow1"/>

===Mental navigation checks===
By mental navigation checks, a pilot or a navigator estimates tracks, distances, and altitudes which will then help the pilot avoid gross navigation errors.<ref>''The Handbook of the SAS and Elite Forces. How the Professionals Fight and Win''. Edited by Jon E. Lewis. p. 370 "Tactics And Techniques, Personal Skills And Techniques". Robinson Publishing Ltd 1997. {{ISBN|1854876759}}</ref>

===Piloting===
{{Further|Pilotage}}
[[File:Navigatie.jpg|thumb|Manual navigation through Dutch airspace]]
Piloting (also called pilotage) involves navigating an aircraft by visual reference to landmarks,<ref name="14cfr1">Federal Aviation Regulations Part 1 §1.1</ref> or a water vessel in restricted waters and fixing its position as precisely as possible at frequent intervals.<ref name="bow105">Bowditch, 2002:105.</ref> More so than in other phases of navigation, proper preparation and attention to detail are important.<ref name="bow105"/> Procedures vary from vessel to vessel, and between military, commercial, and private vessels.<ref name="bow105"/> As pilotage takes place in [[Waves and shallow water|shallow waters]], it typically involves following courses to ensure sufficient [[under keel clearance]], ensuring a sufficient depth of water below the [[Draft (hull)|hull]] as well as a consideration for [[Squat effect|squat]].<ref name="Gilardoni Presedo 2017">{{cite book | last1=Gilardoni | first1=Eduardo O. | last2=Presedo | first2=Juan P. | title=Navigation in Shallow Waters | publisher=[[Witherby Publishing Group]] | publication-place=Livingston, Scotland | date=2017 | isbn=978-1-85609-667-6}}</ref> It may also involve navigating a ship within a river, [[canal]] or [[Channel (geography)|channel]] in close proximity to land.<ref name="Gilardoni Presedo 2017"/>

A military navigation team will nearly always consist of several people.<ref name="bow105"/> 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.<ref name="bow105"/> 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.<ref name="bow105"/> If the ship is equipped with an [[ECDIS]], 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.<ref name="bow105"/> If a [[harbour pilot|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.<ref name="bow105"/> But should the ECDIS fail, the navigator will have to rely on his skill in the manual and time-tested procedures.<ref name="bow105"/>

===Celestial navigation===
{{Main|Celestial navigation}}
[[File:Sun-Moon path.PNG|thumb|upright=1.2|A celestial fix will be at the intersection of two or more circles.]]

Celestial navigation systems are based on observation of the positions of the [[Sun]], [[Moon]], [[planet]]s and [[list of selected stars for navigation|navigational stars]] using a [[sextant]] or similar navigation instrument.<ref name="s102">{{cite web | title=Celestial Navigation | website=Time and Navigation | url=https://timeandnavigation.si.edu/navigating-at-sea/navigating-without-a-clock/celestial-navigation | access-date=2025-02-24}}</ref> 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.<ref name="q565">{{cite book | last=Cunliffe | first=Tom | title=Celestial Navigation | publisher=*Wiley Nautical | publication-place=London | date=2010-09-28 | isbn=978-0-470-66633-3}}</ref> A [[nautical almanac]] and a source of time, typically 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.<ref name="q565"/> 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.<ref name="j728">{{cite book | last=Prinet | first=Dominique F. | title=Celestial Navigation | publisher=FriesenPress | date=2014-07-18 | isbn=978-1-4602-4212-4}}</ref> 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.<ref name="bow269"/> 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.<ref name="t697">{{cite book | last=Karl | first=John | title=Celestial navigation in the GPS age | publisher=Paradiese Cay Publ | publication-place=Arcata,CA | date=2007 | isbn=978-0-939837-75-5}}</ref><ref name="u717">{{cite web | last=Escobar | first=Lieutenant Juan J. | last2=Navy | first2=Chilean | title=Bring Celestial Navigation into the 21st Century | website=U.S. Naval Institute | date=2021-12-01 | url=https://www.usni.org/magazines/proceedings/2021/december/bring-celestial-navigation-21st-century | access-date=2025-02-24}}</ref>

====Marine chronometer====
{{main|Marine chronometer}}
[[File:Breguet marine clock-CnAM 16767-1-IMG 1525-white.jpg|thumb|right|Breguet marine chronometer]]
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.<ref name="bow269">Bowditch, 2002:269.</ref> 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.<ref name="bow269"/> 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.<ref name="bow269"/> The difference between GMT and chronometer time is carefully determined and applied as a correction to all chronometer readings.<ref name="bow269"/> Spring-driven chronometers must be wound at about the same time each day.<ref name="bow269"/>

[[Quartz clock#Accuracy enhancement|Quartz crystal marine chronometers]] have replaced spring-driven chronometers onboard modern ships because of their greater accuracy.<ref name="bow269"/> They are maintained on GMT directly from radio time signals.<ref name="bow269"/> This eliminates chronometer error and watch error corrections.<ref name="bow269"/> Should the second hand be in error by a readable amount, it can be reset electrically.<ref name="bow269"/> The basic element for time generation is a quartz crystal oscillator.<ref name="bow269"/> The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope.<ref name="bow269"/> A calibrated adjustment capability is provided to adjust for the aging of the crystal.<ref name="bow269"/>

The chronometer is typically designed to operate for a minimum of one year on a single set of batteries.<ref name="bow269"/> 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.<ref name="bow269"/> In practice, a wrist watch coordinated to the nearest second with the chronometer will be adequate.<ref name="bow269"/> A stop watch, either spring wound or digital, may also be used for celestial observations.<ref name="bow269"/> 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.<ref name="bow269"/> All chronometers and watches should be checked regularly with a radio time signal.<ref name="bow269"/> Times and frequencies of radio time signals are listed in publications such as [[Radio Navigational Aids]].<ref name="bow269"/>

====The marine sextant====
[[File:Marine sextant.svg|thumb|upright=1.2|The marine [[sextant]] is used to measure the elevation of celestial bodies above the horizon.]]
{{Further|Sextant}}
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").<ref name="q939">{{cite book | last=House | first=D.J. | title=Seamanship Techniques | publisher=Routledge | publication-place=London | date=2013-11-12 | isbn=978-1-135-08015-0 | page=350-252}}</ref> 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.<ref name="q939"/>

There are three main errors that must be corrected in order to each usage for navigation.<ref name="q939"/> The main errors are perpendicular error, side error and index error.<ref name="q939"/> 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.<ref name="q939"/> 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.<ref>{{Cite web |title=How Did Aviators "Shoot" the Sun and Stars? {{!}} Time and Navigation |url=http://timeandnavigation.si.edu/navigating-air/challenges/overcoming-challenges/celestial-navigation |access-date=2023-06-12 |website=timeandnavigation.si.edu |language=en}}</ref>

====Bubble octant====
Until the widespread usage of technologies such as inertial navigation systems, [[VHF omnidirectional range]] and GNSS, air navigators used the [[Bubble octant]] or bubble sextant.<ref name="t804">{{cite book | author=United States. Navy Department | title=Air Navigation: Flying Training | publisher=Air Training Command in accordance with AFR 5-6 | series=Air Force AFM | year=1983 | url=https://books.google.com/books?id=Te-mFCmtDOwC | access-date=2025-02-25 | page=16-1}}</ref> Using this instrument to take sights, mathematical calculations could then be carried out to determine the past position of the aircraft.<ref name="m792">{{cite book | last=Wolper | first=James S. | title=Understanding Mathematics for Aircraft Navigation | publisher=McGraw Hill Professional | date=2001-06-13 | isbn=978-0-07-163879-1 | page=109-150}}</ref>

===Inertial navigation===
{{Further|Inertial navigation system}}

[[Inertial navigation system]] (INS) is a [[dead reckoning]] type of navigation system that computes its position based on motion sensors.<ref name="k075">{{cite book | last=Jekeli | first=Christopher | title=Inertial Navigation Systems with Geodetic Applications | publisher=Walter de Gruyter | publication-place=Berlin | date=2012-10-25 | isbn=978-3-11-080023-4 | page=113}}</ref> 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.<ref name="Tazartes">"An historical perspective on inertial navigation systems", Daniel Tazartes, ''2014 International Symposium on Inertial Sensors and Systems (ISISS)'',  Laguna Beach, CA</ref> 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 but are not now widely found elsewhere.<ref name="Jek296">{{cite book | last=Jekeli | first=Christopher | title=Inertial Navigation Systems with Geodetic Applications | publisher=Walter de Gruyter | publication-place=Berlin | date=2012-10-25 | isbn=978-3-11-080023-4 | page=296}}</ref>

==== Space navigation ====
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 the [[Apollo program]]) via a [[Apollo Guidance Computer|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. 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).<ref name="r120">{{cite web | title=Chapter 13: Navigation | website=NASA Science | date=2023-07-20 | url=https://science.nasa.gov/learn/basics-of-space-flight/chapter13-1/ | access-date=2025-02-24}}</ref>

Another possibility that has been explored for deep space navigation is [[Pulsar-based navigation|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 [[European Space Agency|ESA]].<ref>{{Cite web |title=GSP Executive Summary |url=https://gsp.esa.int/documents/10192/43064675/C4000106174ExS.pdf/8a26a304-9d5f-447d-aa75-bc0c955a4b78 |url-status=dead |website=gsp.esa.int |access-date=2022-12-07 |archive-date=2017-03-16 |archive-url=https://web.archive.org/web/20170316044511/http://gsp.esa.int/documents/10192/43064675/C4000106174ExS.pdf/8a26a304-9d5f-447d-aa75-bc0c955a4b78 }}</ref><ref>{{Cite web |author1=Rafi Letzter |date=2018-04-16 |title=NASA's Got a Plan for a 'Galactic Positioning System' to Save Astronauts Lost in Space |url=https://www.livescience.com/62309-galactic-positioning-system-nasa.html |access-date=2022-12-07 |website=livescience.com |language=en}}</ref>

===Electronic navigation===
[[File:Navigation_system_on_a_merchant_ship_2.jpg|thumb|right|Radar ranges and bearings can be used to determine a position.]]
====Radar navigation====
{{Further|Radar navigation|Doppler radar#navigation}}

Radars can be used for navigation and [[Marine radar|marine radars]] are commonly fitted to ships for navigation at sea.<ref name="e303">{{cite book | title=Safe Nav Watch | publisher=[[Witherby Publishing Group]] | publication-place=Livingston, Scotland | date=2023 | isbn=978-1-914993-46-6 | page=37}}</ref> Radar is an effective aid to navigation because it provides ranges and bearings to objects within range of the radar scanner.<ref name="Anwar133">{{cite book | last = Anwar | first = Nadeem | title = Navigation Advanced for Mates and Masters | edition = 2nd | date = 2015 | publisher = [[Witherby Publishing Group]] | location = Edinburgh | pages=133–139 |isbn = 978-1-85609-627-0}}</ref> 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.<ref name="chap744">Maloney, 2003:744.</ref> A fix consisting of only radar information is called a radar fix.<ref name="bow816">Bowditch, 2002:816.</ref> Types of radar fixes include "range and bearing to a single object,"<ref name="nima163">National Imagery and Mapping Agency, 2001:163.</ref> "two or more bearings,"<ref name="nima163"/> "tangent bearings,"<ref name="nima163"/> and "two or more ranges."<ref name="nima163"/> Radar can also be used with [[ECDIS]] as a means of position fixing with the radar image or distance/bearing overlaid onto an [[Electronic navigational chart|Electronic nautical chart]].<ref name="Anwar133"/>

Parallel indexing is a technique defined by William Burger in the 1957 book ''The Radar Observer's Handbook''.<ref name="nima169">National Imagery and Mapping Agency, 2001:169.</ref> 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.<ref name="nima169"/> This parallel line allows the navigator to maintain a given distance away from [[navigational hazard|hazards]].<ref name="nima169"/> 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.<ref name="Victor">{{cite book | last = Victor| first = Alain| title = Parallel Index Techniques in Restricted Waters -| edition = 2nd | date = 2020 | publisher = [[Witherby Publishing Group]] | location = Edinburgh |isbn = 9781856099165}}</ref>

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.<ref name="nima164">National Imagery and Mapping Agency, 2001:164.</ref> 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.<ref name="nima182">National Imagery and Mapping Agency, 2001:182.</ref> During the transit, the navigator can check that the ship is on track by checking that the pip lies on the drawn line.<ref name="nima182"/>

====Radio navigation====
{{main|Radio navigation|Radio direction finder}}
[[File:Accuracy of Navigation Systems.svg|thumb|upright=1.2]]
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 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 (electronics)|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 [[Germany|German]] [[World War II]] aircraft, as loops under the rear section of the fuselage, whereas most [[United States|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 [[Amplitude modulation|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 is particularly useful due to their high power and location near major cities.

[[Decca Navigator System|Decca]], [[OMEGA Navigation System|OMEGA]], and [[LORAN-C]] are three similar hyperbolic navigation systems. Decca was a [[hyperbola|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 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 platform]]s.

The OMEGA Navigation System was the first truly global [[radio navigation]] system for aircraft, operated by 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&nbsp;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.<ref>{{Cite web |last=Proc |first=Jerry |title=Omega |url=http://www.jproc.ca/hyperbolic/omega.html |access-date=2024-11-22 |website=www.jproc.ca}}</ref> 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 [[radio-navigation|navigation]] system using [[low 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 the [[low frequency]] portion of the EM spectrum from 90 to 110 [[Hertz|kHz]]. Many nations are users of the system, including the [[United States]], [[Japan]], and several European countries. Russia uses a nearly exact system in the same frequency range, called [[CHAYKA]]. LORAN use is in steep decline, with [[Global Positioning System|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.

====Satellite navigation====
{{Further|Satellite navigation}}
[[File:Furuno Electric GPS Navigator GP-80 at Greenpeace's Rainbow Warrior II 20110108.jpg|thumb|right|A ship's Furuno GNSS receiver showing a GPS position]]
A GNSS allow small [[electronics|electronic]] receivers to determine their location ([[longitude]], [[latitude]], and [[altitude]]) within a few meters using [[time signal]]s transmitted along a [[Line-of-sight propagation|line of sight]] by [[radio]] from [[satellite]]s.<ref name="SafeNavWatchGNSS"/> Positions derived can then be used with maps and charts for [[satellite 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 for [[cartography|map-making]] and [[surveying|land surveying]]. GNSS also provides a precise [[time transfer|time reference]] used in many applications including scientific study of [[earthquake]]s, and [[synchronization]] of telecommunications networks. Global Navigation Satellite System or GNSS is the term for satellite navigation systems that provide positioning with global coverage.<ref name="SafeNavWatchGNSS">{{cite book | title=Safe Nav Watch | publisher=[[Witherby Publishing Group]] | publication-place=Livingston, Scotland | date=2023 | isbn=978-1-914993-46-6 | page=34-36}}</ref>  The first system, GPS was developed by the [[United States Department of Defense]] and officially named NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System). The [[satellite constellation]] is managed by the [[United States Air Force]] [[50th Space Wing]]. The cost of maintaining the system is approximately [[United States dollar|US$]]750 million per year,<ref name="GPS overview from JPO">[http://gps.losangeles.af.mil/jpo/gpsoverview.htm GPS Overview from the NAVSTAR Joint Program Office] {{webarchive|url=https://web.archive.org/web/20060928042828/http://gps.losangeles.af.mil/jpo/gpsoverview.htm |date=2006-09-28 }}. Accessed December 15, 2006.</ref> including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as a [[Public good (economics)|public 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 the [[United States]] NAVSTAR [[Global Positioning System]] (GPS), the [[Russia]]n [[GLONASS]], the [[European Union]]'s [[Galileo positioning system]] and the [[Beidou navigation system]] of [[China]].<ref name="SafeNavWatchGNSS"/> 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.<ref name="SafeNavWatchGNSS"/> As a result over 100 satellites are in [[medium Earth orbit]], transmitting signals allowing GNSS receivers to determine the receiver's [[geographic location|location]], speed and direction.<ref name="SafeNavWatchGNSS"/> There are also several regional GNSS systems available for navigation, including the [[Indian Regional Navigation Satellite System]] and the [[Quasi-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.<ref name="SafeNavWatchGNSS"/>

Modern [[smartphones]] act as personal [[GNSS]] 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.<ref>{{Cite journal|last=Gardony|first=Aaron L|date=April 2013|title=How Navigational Aids Impair Spatial Memory: Evidence for Divided Attention|journal=Spatial Cognition & Computation|volume=13|issue=4|pages=319–350|doi=10.1080/13875868.2013.792821|bibcode=2013SpCC...13..319G |s2cid=7905481}}</ref><ref>{{Cite journal|last=Gardony|first=Aaron L.|date=June 2015|title=Navigational Aids and Spatial Memory Impairment: The Role of Divided Attention|journal=Spatial Cognition & Computation|volume=15|issue=4|pages=246–284|doi=10.1080/13875868.2015.1059432|bibcode=2015SpCC...15..246G |s2cid=42070277}}</ref><ref>{{Cite book|title=Spatial Information Theory|last=Winter|first=Stephen|publisher=Springer Berlin|year=2007|isbn=978-3540747888|location=Heidelberg, Germany|pages=238–254}}</ref> Typically a [[compass]] is also provided to determine direction when not moving.

==== Acoustic navigation ====
{{main|Sonar|Acoustic location}}

[[Acoustic location]] is a method of navigation by the use of acoustic positioning systems which determine the position of an object by using [[sound waves]]. It is primarily used by [[submarines]] and ships fitted with [[sonar]] and similar transducer based technologies.<ref name="l124">{{cite book | last1=Christ | first1=Robert D. | last2=Wernli | first2=Robert L. | title=The ROV Manual | chapter=Practical Applications | publisher=Elsevier | year=2014 | isbn=978-0-08-098288-5 | doi=10.1016/b978-0-08-098288-5.00021-x | pages=561–599}}</ref><ref name="k448">{{cite web | title=Long Range Acoustic Communications and Navigation in the Arctic | url=https://acomms.whoi.edu/wp-content/uploads/sites/20/2016/11/FreitagBallPartanKoskiSingh_Arctic_2015.pdf | publisher=Woods Hole Oceanographic Institution |access-date=2025-02-24}}</ref> [[Underwater acoustic positioning system]]s are also commonly used by divers and [[Remotely operated underwater vehicle]]s, specifically the [[Long baseline acoustic positioning system]], the [[Short baseline acoustic positioning system]] and the [[Ultra-short baseline acoustic positioning system]].<ref name="l124"/><ref name="c798">{{cite web | title=Precision acoustic navigation for remotely operated vehicles (ROV) | url=https://bibliotekanauki.pl/articles/985799.pdf | publisher=Hydroacoustics, 2005 - bibliotekanauki.pl| access-date=2025-02-24}}</ref>