Marine navigation is the art and science of steering a ship from a starting point (sailing) to a destination, efficiently and responsibly. It is an art because of the skill that the navigator must have to avoid the dangers of navigation, and it is a science because it is based on physical, mathematical, oceanographic, cartographic, astronomical, and other knowledge.
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Marine navigation can be surface or submarine.
Navigation (from the Latin word navigatio) is the act of sailing or voyaging. Nautical (from Latin nautĭca, and this from Greek ναυτική [τέχνη] nautikḗ [téjne] "[art of] sailing" and from ναύτης nautes "sailor") is that pertaining to navigation and the science and art of sailing. Naval (from the Latin adjective navalis) is that relating to ships and navigation, or particularly to the navy.[1]
In Ancient Rome, the navicularii conducted long-distance trade by sea.
Coastal navigation was practiced since the most ancient times.[2] The biblical account of the great flood, where the Noah's Ark appears, is based both on myths and on the navigational practice of the Mesopotamian civilizations, who from the Sumerians onwards navigated their two rivers (Tigris and Euphrates) and the Persian Gulf. The ancient Egyptians did not limit themselves to inland navigation of the Nile either, and used the Mediterranean sea routes existing since the Neolithic — through which cultural phenomena such as megalithism or the metallurgy would have spread for millennia. The Cretans even established a true thalassocracy (government of the seas, attributed to King Minos) until the Mycenaean period (2nd millennium BC), when the events mythologized in the Homeric poems[Note 1] ought to be placed.
The Hittites, led by King Šuppiluliuma II faced the Cyprus in the first historically recorded naval battle (ca. BC); at the same time, all the civilizations of the Eastern Mediterranean suffered from the incursions of the denominated "Sea Peoples".
The Phoenicians — whom the Greeks considered their masters in navigation and who are also cited in the Bible —[Note 2][3] would have been the first Mediterranean civilization to sail the high seas by sculling and sailing, guided by the sun during the day and by the North Star at night. It is recorded that, crossing the Strait of Gibraltar — the "Rock of Gibraltar", the so-called "Pillars of Hercules" in the Greek myths — they sailed across the Atlantic Ocean reaching the south to some point on the west coast of Africa and the north to the British Isles (or even beyond, to the place that the texts call Thule), but it is unclear if they circumnavigated Africa or crossed the Atlantic reaching America, something most likely achieved by the Norsemen in the 10th century.
In the Indian and Pacific oceans, the oceanic navigations made it possible to populate all the archipelagoes (Polynesian navigation). However, the possibility of reaching South America is still a matter of debate — the settlement of the Americas through the Bering Strait would not have required navigation, or in any case, coastal navigation would have sufficed — as well as other possible pre-Columbian transoceanic contacts. In the first quarter of the 15th century, the Chinese expeditions led by Zheng He reached the African coasts of the Indian Ocean. It has been proposed that they might have reached the South Atlantic and even America and Europe, but this proposal has not been accepted beyond mere speculation.
Mediterranean navigation, which the Romans had come to control (undisputed Mare Nostrum since their victories over the Carthaginians in the Punic Wars [264-146 BC], the Egyptians during the Battle of Actium [31 BC], and pirates), was once again a contested environment in the Middle Ages, from the moment the Vandals managed to attack the Italian coasts from the sea. In the 6th century, the Byzantines managed to regain control, and in the 7th century it was the Arabs who ended up dividing the Mediterranean area,[5] which even the Vikings and Normans were able to access. Since the time of the Crusades, Venetian,[6] Genoese[7] and Crown of Aragon[8] navigators also had a strong presence. Knowledge of the compass, transmitted to the Europeans by the Arabs (who in turn had obtained it from the Chinese), together with other improvements in astronomical techniques (astrolabe, Jacob's staff, sextant, cartographic techniques (portulan and shipbuilding (caravel, nau, galleon), made the Age of Discovery — initially led by the Portuguese and Castilians — possible, especially after Henry the Navigator impulsed the school of Sagres. In , the first voyage of Christopher Columbus took place. In , Bartolomeu Dias rounded the Cape of Good Hope, which opened the route to the Indian Ocean — Vasco de Gama reached Calicut (India) in . Between and , the Magellan-Elcano expedition circumnavigated the world — measuring the geographical longitude with the method of its scientific organizer, Rui Faleiro. Until the 6th century, the Spanish-Portuguese hegemony in navigation was patent in fields such as geography and cosmography. Both English and French pilots learned to navigate from the texts of Pedro de Medina, Martín Fernández de Enciso and Martín Cortés, among others.[9][10] The conjunction of "cannons and sails" has been argued to have given European states the advantage to prevail over the rest,[11] launching the modern "world system".[12]
Since the 18th century, England exercised maritime hegemony, a fact that was confirmed in the early 19th century with the Battle of Trafalgar (). Among the main English expeditions of the time were Captain Cook's (-), also the second expedition of the Beagle (-) — which was of great importance for the later development of Charles Darwin's theory of evolution. Already fully in the age of steam navigation, techniques and vessels continued to be perfected in transoceanic sailing (clipper), that did not become obsolete for commercial navigation until the 20th century — especially after the opening of the Panama Canal. Even then, the unbridled optimism that characterized the naval design of the time suffered a severe blow with the sinking of the Titanic ().
Contemporary shipping has massively ceased to perform one of its traditional functions and has been replaced by aviation, such as passenger transport, although with two important exceptions: leisure travel (tourism by cruise ships) and irregular traffic of people (irregular immigration). Since the Second Industrial Revolution, the main volume of freight transport has been hydrocarbons (oil tankers and gas tankers). Other raw materials are also transported in bulk on cargo ships, but from onward, a large part of goods of all kinds were adapted to standardized containers that speed up loading and unloading, allowing a combination with land transport (hub). Highly technological navigation has reduced crews and increased the size of ships. For example, in deep-sea fishing, which locates its prey with sophisticated means and lasts indefinitely in time — freezer ships or factory ships — which in some circumstances has made them vulnerable to new forms of piracy.
These are the methods used in maritime navigation to solve the three problems of the navigator:
Navigation and location of the ship by positioning techniques based on the observation of bearings and distances to notable points on the coast (lighthouses, capes, buoys, etc.) by visual means (pelorus), observation of horizontal angles (sextant) or electronic methods (bearings from radar to racons, transponders, etc.)
Navigation and location of the ship by analytical means, after considering the following elements: initial location, bearing(s) — whether absolute bearings, surface bearings, or relative bearings. Also velocity as well as the external factors that have influenced the course either partially or entirely, such as the wind (leeway) and/or the current (bearing of the current and hourly current intensity). The point obtained from the calculations is called the "Dead reckoning location", with its corresponding latitude and longitude. This point is also known as Fantasy point.
Navigation that follows a rhumb line — that is, all meridians are cut at the same angle. On a nautical chart following the Mercator projection, a loxodromic is represented by a straight line.
This type of navigation is useful for not too long distances, as it allows the course to remain steady,[16] but it does not offer the shortest distance.
Navigation that follows the shortest distance between two points, i.e., that which follows a great circle. Such routes yield the shortest distance between two points on the globe.[16] To calculate the bearing and distance between two points it is necessary to solve a spherical triangle whose vertices are the origin, the destination, and the pole.[17]
Navigation and location of the ship by geopositioning techniques based on the observation of the stars and other celestial bodies. The variables measured to find the location are: the observed angular height of the stars above the horizon, measured with the sextant (formerly with the astrolabe or other instrument), and the time, measured with the chronometer.
Conceptually, the process is not complex to understand:
In practice, the mathematical process, called "reduction" of the observation, can be complex for the uninitiated. To the height observed with the sextant, it is necessary to apply a series of corrections to compensate for atmospheric refraction, parallax and other errors. Once this is done, it is necessary to solve a spherical triangle by mathematical and trigonometric methods.
There are many methods to do this. The manual methods use tables (trigonometric, logarithms, etc.) to facilitate the calculations. The introduction of calculators and electronic computers at the end of the 20th century greatly facilitated the calculation, but the creation of GPS made celestial navigation no longer important, relegating it to the background as an alternative method in case of failure of the on-board electronics or as a hobby of scientific interest.
Navigation and location of the ship by positioning techniques based on the aids provided by global positioning systems, such as GPS, GLONASS, or GALILEO. It is the system most widely spread and easiest to use, in spite of the errors that may arise.
Navigation and location of the ship by means of the analysis of the data provided by accelerometers and/or gyroscopes located on board, which integrate the accelerations experienced in complex electronic systems, that converted into velocities (in the 3 possible axes of displacement) and according to the observed courses, make it possible to obtain the location of the ship.
The harbinger of a successful navigation was the dolphin, which is why its representation became the symbol carried by all ships.
More recently, navigation was represented as a woman crowned with ship's sterns whose clothes are agitated by the winds. She rests one hand on a rudder and the other holds the instrument for measuring height. At her feet, the ampoule, the compass, the trident of Neptune and the riches of commerce, while the sea can be seen on the horizon, completed by a lighthouse and traversed by ships at full sail.[10]
The navigation equipment of the vessel consists of a set of devices that determine the ship's position, speed, course, and also ensure safety during navigation in shallow waters or when meeting other vessels. Some of them have been used by seafarers for a long time, while others represent new technologies.
All bridge equipment should be regularly checked and tested. The list of the minimum shipborne navigational equipment depends on the tonnage of the vessel, its destination and date of construction. It is defined by SOLAS Chapter V, Regulation 19.
So, an overview of the navigation equipment used on merchant ships today.
The oldest and most commonly used type of compass. In navigation, this tool is applied to determine the northern direction by the Earth's magnetic field.
The gyro compass is the prime navigational device used on ships and submarines. Its principle of operation is based on the use of the properties of the gyroscope and the daily rotation of the Earth.
The gyro compass is superior to the magnetic one, because there can be no errors caused by magnetic fields: it finds the true North Pole of the Earth (navigationally more useful), while the magnetic compass finds the magnetic North Pole.
Rapid changes in course, speed or latitude cause deviations in the measurements after which the gyro adjusts itself. Most modern ships have satellite navigation systems (such as GPS) or other navigation tools that transmit data to the built-in gyro compass computer for correction.
ECDIS (Electronic Chart Display and Information System) is the pinnacle of modern navigation computer technologies, a digital alternative to paper nautical charts.
The system is connected to other navigational equipment on ship such as the GNSS (GPS), AIS, gyro compass, autopilot, speed log, radar/ARPA, NAVTEX, echo sounder and others. Based on the processed data, ECDIS displays maps and the location of the vessel, plots the route and monitors deviations from the planned route, calculates safe courses, warns the navigation officer about danger, keeps a ship's log and provides many other sophisticated navigation and safety functions. Thus, ECDIS significantly reduces the burden on the navigator, which frees up time for better monitoring of the surrounding circumstances and making informed decisions on ship management.
With the help of radar, any target around the vessel can be detected: ships, land obstacles, icebergs, etc. For this purpose, a rotating antenna is used. The picture of the ship’s surroundings is displayed on the device screen. This data can be used to avoid collisions and is especially useful in adverse weather conditions.
There are 2 types of radars used on ships: X-band and S-band radars. X-band radar operates at a frequency of about 10 GHz and with a wavelength of 3 cm (smaller antennas in weight and size). Being of higher frequency, this band provides a better target resolution.
The S-band radar operates at a frequency of 3 GHz with a wavelength of 10 cm (a larger antenna on the mast). This band is more resistant to interference than the X-band, and provides more accurate data during heavy rain or snow.
ARPA (Automatic Radar Plotting Aid) is a computer system that processes radar data and creates tracks for vessels within the radar coverage of the ship.
Using advanced technologies, ARPA not only represents the current situation, but also predicts future situations. The system calculates the course of the tracked objects, their speed, time and distance necessary for safe passage with other vessels. If necessary, the user can get more detailed information on selected targets.
Like ARPA, the ATA (Automatic Tracking Aid) device displays information about the tracked target in graphical and numerical form using radar contacts. This allows the officer of the watch to plan a safer course without collisions.
At the time, this device made a technological breakthrough in maritime navigation.
Autopilot is a truly indispensable component of the bridge’s navigational equipment. This is a system (electronic or hydraulic) designed to automatically control the steering mechanism of a vessel and maintain it on a set course. By holding the steering in autopilot mode, the navigator can focus on other critical tasks such as collision risk assessment and avoidance.
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The device is synchronized with the gyro compass. If the latter has any malfunctions, they will affect the steering of the vessel. In case of gyro compass failure, the system will lose the ability to control the vessel.
Modern autopilot systems can also be synchronized with ECDIS, which allows them to follow the route laid out on the electronic chart.
Autopilot cannot completely replace a human. The vessel must be operated manually when navigating in restricted waters and high-density traffic areas.
AIS (Automatic Identification System) is an automatic tracking system that serves to identify ships, their dimensions, course, speed, position and other data using VHF radio waves (frequencies 161.975 MHz and 162.025 MHz). Its main task is to reduce the risk of ship collisions.
Unlike radars, which are able to detect the appearance of large floating objects near the ship and approximately estimate their current direction and speed, AIS provides much more detailed and accurate information about the navigation situation. It is displayed on the screen of the AIS station or ECDIS.
Vessels equipped with AIS must constantly maintain it in operation. An exception is made in cases where international agreements provide for the protection of navigational information.
This type of navigation device relies on GPS (Global Positioning System) technology using satellites. It determines with a high degree of accuracy the coordinates of the vessel, its speed, course and time required to cover the distance between two given points.
GPS technology can also help avoid ship collisions and alert emergency services in the event of an accident.
This instrument indicates the current position of the rudder blade. It is usually installed near the steering wheel, on the wings of the bridge and in the engine room.
This navigation device measures the speed and distance passed by the vessel from a given point. It is used to calculate the expected time of the ship's entry into port. The data is transmitted to the port authorities.
Global Maritime Distress and Safety System (GMDSS) uses Earth and satellite technologies, as well as ship radio systems. The components of this system on the ship are VHF, MF/HF with DSC, Navtex, radiotelex, SART, EPIRB, Inmarsat-C.
The GMDSS console is used to notify the coastal services of emergency situations with vessels, as well as to receive maritime safety messages and to communicate with other ships by radio.
VDR (Voyage Data Recorder) is a device similar to a black box carried on aircraft. Extremely important navigation equipment that continuously records all the information necessary for further investigation in case of an accident on board.
There are different types of data loggers, but they all provide data for the last 12-24 hours prior to an emergency.
This device is more than 100 years old. It is used to measure the depth under the vessel by sending a sound pulse, which bounces off the bottom and returns back to the source.
Rate of turn indicator (ROTI) shows the speed at which the ship turns at a fixed angle of rotation of the rudder. The turning speed is measured in degrees per minute.
There are two types of ROTIs: digital and analog.
The analog type of device is compulsory, it calculates the turning speed faster and more correctly, so it is still the most installed type on board ships. As for the digital type, it can be used as an analog type repeater.
ROTI is installed on the ship as an independent device integrated with the steering/autopilot.
LRIT (Long Range Identification and Tracking) is an international vessel tracking and identification system established by the IMO. It is aimed at enhancing the security of shipping and ensuring the protection of the marine environment.
According to SOLAS Chapter V, Regulation 19.1, the following types of vessels are required to transmit information to the LRIT system during their international voyages:
passenger ships, including high-speed passenger craft;
cargo ships, including high-speed craft, of 300 gross tons and above, and
mobile offshore drilling units.
BNWAS (Bridge Navigation Watch and Alarm System) is another important automated system used on ships. The mechanism emits a nasty sound every 3, 9 or 12 minutes until the necessary button is pressed.
BNWAS thus warns the ship's captain or other boatmasters if the officer on watch does not respond and cannot perform his duties on the bridge. The consequences of this may be severe. Sometimes even 5 minutes is enough for an accident to occur with a vessel left unattended.
This system shall always be in operation and may be deactivated by the master of the ship only if he deems it necessary.
This acoustic system is necessary on ships with a fully enclosed bridge. It allows the navigating officer inside the cabin to hear external signals of ships, coastal stations and other objects.
The device is built into the navigation console and helps the officer to keep watch according to the rules of COLREGs (Convention on the International Regulations for Preventing Collisions at Sea).
This device is also called a typhon, a horn or a foghorn. The ship's whistle is used in difficult navigation situations, such as poor visibility, heavy traffic, etc. It also helps to warn the crew and other vessels nearby about an emergency on board.
The ship's horn is usually duplicated. One works under air pressure, and the other is powered by electricity. They should be operated both manually and electrically from the bridge.
In addition to the sound signals, there are also warning lights for emergency situations, which can also be used at night. Like other ship emergency equipment, the lamp can be powered not only from the ship's main electrical system, but also from emergency batteries.
All vessels, both small and large, are required to have identification lights that give information about their type, size and moving direction. Nav lights are used to prevent collisions with other vessels at night or during periods of reduced visibility.
Signal flags have been used in navigation since ancient times. At present, 4 dozen flags are used, each of them has its own meaning. They are described in the International Code of Signals. For example, a flag with the letter equivalent "B/Bravo" means "I am taking in or discharging or carrying dangerous goods", while a flag with the letters "L/Lima" means "You should stop your vessel immediately", etc.
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These are the main types of navigation equipment of modern ships. Thanks to the advanced technologies used, navigation has become more efficient and safe than ever before.
By Olga Davydova and Julia Zhyvotova
It may be interesting:
Global Maritime Distress and Safety System
GMDSS equipment carriage requirements
Shipborne Automatic Identification System (AIS)
Communication Systems in the Maritime Industry
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