Navigation is the process of planning, reading, and controlling the movement of a craft or vehicle from one place to another.  The word navigate is derived from the Latin roots navis meaning "ship" and agere meaning "to move" or "to direct. " All navigational techniques involve locating the navigator's position compared to known locations or patterns.
|Map of Earth|
|Lines of longitude appear curved in this projection, but are actually halves of great circles. A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, Regions, and Themes EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement|
|Lines of latitude appear horizontal in this projection, but are actually circular with different radii. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the In Astronomy, Geography, Geometry and related sciences and contexts a plane is said to be horizontal at a given point if it is locally All locations with a given latitude are collectively referred to as a circle of latitude. A circle of latitude, on the Earth, is an imaginary East - West circle connecting all locations (not taking into account elevation that share a given|
|The equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0°. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball'|
The latitude of a place on the earth's surface is the angular distance north or south of the [equator]. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the  Latitude is usually expressed in degrees (marked with °) ranging from 0° at the Equator to 90° at the North and South poles. This article describes the unit of angle For other meanings see Degree. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the  The latitude of the North Pole is 90° N, and the latitude of the South Pole is 90° S. The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is subject to the caveats explained below defined as the point in the northern The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the southernmost point on the surface of the Earth.  Historically, mariners calculated latitude by sighting the sun with a sextant in conjunction with a compass. This article is about the sextant as used for Navigation. For the astronomer's sextant, see Sextant (astronomical. A compass, magnetic compass or mariner's compass is a navigational instrument for determining direction relative to the earth's Magnetic poles It consists
Similar to latitude, the longitude of a place on the earth's surface is the angular distance east or west of the prime meridian or Greenwich meridian. Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement The Prime Meridian is the meridian (line of Longitude) at which longitude is defined to be 0° The Prime Meridian is the meridian (line of Longitude) at which longitude is defined to be 0°  Longitude is usually expressed in degrees (marked with °) ranging from 0° at the Greenwich meridian to 180° east and west. This article describes the unit of angle For other meanings see Degree. Sydney, Australia, for example, has a longitude of about 151° east. Sydney (ˈsɪdniː is the most populous city in Australia, with a Metropolitan area population of approximately 4 New York City has a longitude of about 74° west. The City of New York For most of history, mariners struggled to determine precise longitude. The problem was solved with the invention of the marine chronometer. A marine chronometer is a timekeeper precise enough to be used as a portable Time standard; it can therefore be used to determine Longitude by means of Celestial Longitude can be calculated if the precise time of a sextant sighting is known.
Most modern navigation relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on crossing lines of position or LOP. A position line is a line that can be identified both on a Nautical chart or Aeronautical chart and by observation out on the surface of the Earth.  A line of position can refer to two different things: a line on a chart and 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 on that line on the chart. A nautical chart is a graphic representation of a maritime area and adjacent Coastal regions 
In addition to bearings, navigators also often measure distances to objects.  On the chart, a distance produces a circle or arc of position.  Circles, arcs, and hyperbolae of positions are often referred to as lines of position.
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 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 the table.
|Modern navigation methods|
|Dead reckoning or DR, in which one advances a prior position using the ship's course and speed. Dead reckoning ( DR) is the process of estimating one's current position based upon a previously determined position or fix, and advancing that position based upon 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. Leeway is the lateral movement of a ship to the Leeward of her course drift An inertial navigator develops an extremely accurate EP. An Inertial Navigation System (INS is a Navigation aid that uses a Computer and motion sensors to continuously track the position orientation and Velocity ||Used at all times.|
|Pilotage involves navigating in restricted waters with frequent determination of position relative to geographic and hydrographic features. Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination sometimes with the help of a Map or Nautical ||When within sight of land.|
|Celestial navigation involves reducing celestial measurements to lines of position using tables, spherical trigonometry, and almanacs. Celestial navigation, also known as astronavigation, is a Position fixing technique that was devised to help sailors cross the featureless oceans without having to Spherical trigonometry is a part of Spherical geometry that deals with Polygons (especially Triangles on the Sphere and explains how to find relations A nautical almanac is a publication describing the positions and movements of Celestial bodies for the purpose of enabling navigators to use Celestial navigation||Used primarily as a backup to satellite and other electronic systems in the open ocean. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage |
|Electronic navigation covers any method of position fixing using electronic means, including:|
|Radio navigation uses radio waves to determine position by either radio direction finding systems or hyperbolic systems, such as Decca, Omega and LORAN-C. Radio navigation or radionavigation is the application of Radio frequencies to determining a position on the Earth. A radio direction finder ( RDF) is a device for finding the direction to a Radio source The Decca Navigator System was a hyperbolic Low frequency Radio navigation system (also known as Multilateration) that was first deployed during OMEGA was the first truly global Radio navigation system for aircraft operated by the United States in cooperation with six partner nations LORAN ( LO ng R ange A id to N avigation is a terrestrial Radio navigation system using Low frequency Radio transmitters||Losing ground to GPS.|
|Radar navigation uses radar to determine the distance from or bearing of objects whose position is known. See also Navigation, Radar radar systems can provide very useful navigation information in a variety of situations This process is separate from radar’s use as a collision avoidance system. ||Primarily when within radar range of land.|
|Satellite navigation uses artificial earth satellite systems, such as GPS, to determine position. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage ||Used in all situations.|
The practice of navigation usually involves a combination of these different methods. 
Dead reckoning is the process of estimating present position by projecting course and speed from a known past position.  It is also used to predict a future position by projecting course and speed from a known present position.  The DR position is only an approximate position because it does not allow for the effect of leeway, current, helmsman error, compass error, or any other external influences. 
The navigator uses dead reckoning in many ways, such as:
The most important use of dead reckoning is to project the position of the ship into the immediate future and avoid hazards to navigation. 
The navigator carefully tends the DR plot, updating it when required, and uses it to evaluate external forces acting on the ship. The navigator also consults the DR plot to avoid navigation hazards.  A fix taken at each DR position will reveal the effects of current, wind, and steering error, and allow the navigator to stay on track by correcting for them. 
The use of DR when an Electronic Charts Display and Information System (ECDIS) is the primary plotting method will vary with the type of system. An Electronic Chart Display and Information System (ECDIS is a specific form of computer-based navigation information system that complies with International Maritime Organization An ECDIS allows the display of the ship’s heading projected out to some future position as a function of time, the display of waypoint information, and progress toward each waypoint in turn. 
Until ECDIS is proven to provide the level of safety and accuracy required, the use of a traditional DR plot on paper charts is a prudent backup, especially in restricted waters. 
Before the development of the lunar distance method or the marine chronometer, dead reckoning was the primary method of determining longitude available to mariners such as Christopher Columbus and John Cabot on their trans-Atlantic voyages. In Celestial navigation, lunar distance is the angle between the Moon and another Celestial body. A marine chronometer is a timekeeper precise enough to be used as a portable Time standard; it can therefore be used to determine Longitude by means of Celestial Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement Christopher Columbus (1451 &ndash May 20 1506 was an Italian Navigator, colonizer Giovanni Caboto ( c 1450 - c 1498 known in English as John Cabot, was an Italian Navigator and explorer commonly credited as the
Piloting (also called pilotage) involves navigating a vessel in restricted waters and fixing its position as precisely as possible at frequent intervals. Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination sometimes with the help of a Map or Nautical  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. 
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 the civilian navigator must often take and plot them himself.  While the military navigator will have a bearing book and someone to record entries for each fix, the civilian navigator will simply plot the bearings on the chart as they are taken and not record them at all. 
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.  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. A pilot is a Mariner who guides Ships through dangerous or congested waters such as Harbours or River mouths Legally the master remains  But should the ECDIS fail, 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. The Sun (Sol is the Star at the center of the Solar System. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is The navigational stars are used in Celestial navigation because they are some of the brightest celesital objects due to their high luminosities and/or their proximity 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 the observer's horizon, the navigator can determine his distance from that subpoint. A Nautical almanac and a 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. A nautical almanac is a publication describing the positions and movements of Celestial bodies for the purpose of enabling navigators to use Celestial navigation A chronometer watch is a Watch tested and certified to meet certain precision standards This article is about the sextant as used for Navigation. For the astronomer's sextant, see Sextant (astronomical. That height can then be used to compute distance from the subpoint to create a circular line of position. 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. 
In order to accurately measure longitude, the precise time of a sextant sighting (down to the second, if possible) must be recorded.
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 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 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 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 1 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 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. 
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").
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.
Adjustment of the sextant consists of checking and aligning all the optical elements to eliminate "index correction". Index correction should be checked, using 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 is a dead reckoning type of navigation system that computes its position based on motion sensors. An Inertial Navigation System (INS is a Navigation aid that uses a Computer and motion sensors to continuously track the position orientation and Velocity An Inertial Navigation System (INS is a Navigation aid that uses a Computer and motion sensors to continuously track the position orientation and Velocity Dead reckoning ( DR) is the process of estimating one's current position based upon a previously determined position or fix, and advancing that position based upon Once the initial latitude and longitude is established, the system receives impulses from motion detectors that measure the acceleration along three or more axes enabling it continually and accurately to calculate the current latitude and longitude. Its advantages over other navigation systems are that, once the starting position is set, it does not require outside information, it is not affected by adverse weather conditions and it cannot be detected or jammed by the enemy. The US Navy developed a Ships Inertial Navigation System (SINS) during the Polaris missile program to insure a safe, reliable and accurate navigation system for its missile submarines. The Polaris missile was a submarine-launched two-stage solid-fuel nuclear-armed ballistic missile ( SLBM) built during the Cold War by Lockheed for Inertial navigation systems were in wide use until satellite navigation systems (GPS) became available. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage
A radio direction finder or RDF is a device for finding the direction to a radio source. A radio direction finder ( RDF) is a device for finding the direction to a Radio source Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. 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 and listening for the direction in which the signal from a known station comes through most strongly. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into This sort of system was widely used in the 1930s and 1940s. The 1930s were described as an abrupt shift to more radical and conservative lifestyles as countries were struggling to find a solution to the Great Depression. The 1940s decade ran from 1940 to 1949 Events and trends The 1940s was a period between the radical 1930s and the conservative 1950s which also leads the period to be RDF antennas are easy to spot on German World War II aircraft, as loops under the rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including The United States of America —commonly referred to as the
In navigational applications, RDF signals are provided in the form of radio beacons, the radio version of a lighthouse. A lighthouse is a Tower, building or framework designed to emit light from a system of lamps and lenses or in older times from a fire and used as an 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". Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals 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, and LORAN-C are three similar hyperbolic navigation systems. The Decca Navigator System was a hyperbolic Low frequency Radio navigation system (also known as Multilateration) that was first deployed during OMEGA was the first truly global Radio navigation system for aircraft operated by the United States in cooperation with six partner nations LORAN ( LO ng R ange A id to N avigation is a terrestrial Radio navigation system using Low frequency Radio transmitters 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. In Geometry, a hyperbola ( Greek, "over-thrown" has several equivalent definitions Low Frequency or LF refers to Radio Frequencies (RF in the range of 30 kHz&ndash300 kHz Radio navigation or radionavigation is the application of Radio frequencies to determining a position on the Earth. Multilateration, also known as hyperbolic positioning, is the process of locating an object by accurately computing the time difference of arrival ( TDOA World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including As was the case with Loran C, its primary use was for ship navigation in coastal waters. LORAN ( LO ng R ange A id to N avigation is a terrestrial Radio navigation system using Low frequency Radio transmitters 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. An oil platform or oil rig is a large structure used to house workers and machinery needed to drill and/or extract oil and Natural gas through wells After being shut down in the spring of 2000, it has been superseded by systems such as the American GPS and the planned European Galileo positioning system. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Galileo is a Global navigation satellite system currently being built by the European Union (EU and European Space Agency (ESA
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. Radio navigation or radionavigation is the application of Radio frequencies to determining a position on the Earth. The United States of America —commonly referred to as the 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 accuracy when fixing a position. Year 1968 ( MCMLXVIII) was a Leap year starting on Monday (link will display full calendar of the Gregorian calendar. Initially, the system was to be used for navigating nuclear bombers across 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. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Omega was terminated on September 30, 1997 and all stations ceased operation. Events 1399 - Henry IV is proclaimed King of England. 1744 - France and Spain defeat the Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar
LORAN is a terrestrial 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. Radio navigation or radionavigation is the application of Radio frequencies to determining a position on the Earth. Low Frequency or LF refers to Radio Frequencies (RF in the range of 30 kHz&ndash300 kHz 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. Low Frequency or LF refers to Radio Frequencies (RF in the range of 30 kHz&ndash300 kHz The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. Many nations are users of the system, including the United States, Japan, and several European countries. The United States of America —commonly referred to as the For a topic outline on this subject see List of basic Japan topics. Russia uses a nearly exact system in the same frequency range, called CHAYKA. Chayka (Чайка lit seagull) is a Russian terrestrial Radio navigation system similar to LORAN-C. LORAN use is in steep decline, with GPS being the primary replacement. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth However, there are attempts to enhance and re-popularize LORAN.
When a vessel is within radar range of land or special radar aids to navigation, 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. 
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 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. 
Some techniques 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 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. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage A GNSS allow small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line of sight by radio from satellites. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the Altitude is the Elevation of a point or object from a known level or datum (plural data The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International A time signal is a visible audible mechanical or electronic signal used as a reference to determine the time of day Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. 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 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The United States of America —commonly referred to as the Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth The Russian GLONASS is a GNSS in the process of being restored to full operation. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending The European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in Galileo is a Global navigation satellite system currently being built by the European Union (EU and European Space Agency (ESA China has indicated it may expand its regional Beidou navigation system into a global system. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Beidou Navigation System ( or Beidou Satellite Navigation and Positioning System ( is a project by China to develop an independent Satellite navigation
More than two dozen GPS satellites are in medium Earth orbit, transmitting signals allowing GPS receivers to determine the receiver's location, speed and direction. Medium Earth Orbit (MEO, sometimes called Intermediate Circular Orbit (ICO is the region of space around the Earth above low Earth orbit ( and below Geostationary orbit A geographic coordinate system enables every location on the Earth to be specified in three coordinates using mainly a spherical coordinate system.
Since the first experimental satellite was launched in 1978, GPS has become an indispensable aid to navigation around the world, and an important tool for map-making and land surveying. Surveying is the technique and science of accurately determining the terrestrial or three-dimensional space Position of points and the distances and angles between GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks. Time transfer describes methods for transferring reference clock Synchronization from one point to another often over long distances An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer
Developed by the United States Department of Defense, GPS is officially named NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System). The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government The satellite constellation is managed by the United States Air Force 50th Space Wing. A group of electronic Satellites working in concert is known as a satellite constellation. The 50th Space Wing ( 50 SW) is a wing of the United States Air Force under the major command of Air Force Space Command (AFSPC The cost of maintaining the system is approximately US$750 million per year, including the replacement of aging satellites, and research and development. The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been Despite this fact, GPS is free for civilian use as a public good. In Economics, a public good is a good that is non-rivaled and non-excludable.
The Day's work in navigation is a minimal set of tasks consistent with prudent navigation. The definition will vary on military and civilian vessels, and from ship to ship, but takes a form resembling:
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 enroute portion of a voyage, approaching the destination, and mooring. vessel is said to be moored when it is fastened to a fixed object such as a Pier, Quay or the seabed or to a floating object such as an anchor buoy According to international law, a vessel's captain is legally responsible for passage planning, however on larger vessels, the task will be delegated to the ship's navigator. Captain is the traditional customary title given to the person in charge in command of a Ship at sea A navigator is the person onboard a ship or aircraft responsible for its Navigation. 
Studies show that human 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.  The practice of voyage planning has evolved from penciling lines on nautical charts to a process of risk management. A nautical chart is a graphic representation of a maritime area and adjacent Coastal regions For non-business risks see Risk or the disambiguation page Risk analysis. 
Passage planning consists of four stages: appraisal, planning, execution, and monitoring, which are specified in International Maritime Organization Resolution A. The International Maritime Organization ( IMO) formerly known as the Inter-Governmental Maritime Consultative Organization ( IMCO) is a late 20th century 893(21), Guidelines For Voyage Planning, 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 and publications. The Code of Federal Regulations (CFR is the codification of the general and permanent rules and regulations (sometimes called administrative law) published in the 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. 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.
Electronic integrated bridge concepts are driving future navigation system planning.  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.  The navigator becomes a system manager, choosing system presets, interpreting system output, and monitoring vessel response.