The early seafarers probably stayed within easy reach of the coast and did not go to sea at night or when the weather was likely to be bad.  In the Middle Ages, European seafarers generally did not go to sea during the winter months. But while this seemed sensible at the time, such caution naturally restricted their movements.  Long, ocean voyages inevitably involved risk.

Old ShipApart from the weather, the greatest challenge for early seafarers was finding their way.  Without maps or adequate experience to guide them, they usually had no way of knowing what lay beyond the horizon.  If they did know that something was there, they did not have the knowledge necessary to reach it and to get back.  The seafarer might imagine he was going in a straight line, yet winds and currents were always threatening to take the ship off course.  Navigation was even more difficult at night and in bad weather, when stars or landmarks such as islands would be hidden from view.  For the seafarer, therefore, the most important challenge after simply staying afloat was knowing where he was.

Today, technology has solved many of these problems.  But the Lloyd's Register of Shipping Casualty Returns for 1958 - the year before the International Maritime Organization met for the first time - showed that 16 per cent of the merchant shipping tonnage lost that year (56,000 gt) resulted from collisions and a further 32 per cent (115,000 gt) from groundings or striking wrecks.   The vast majority of these casualties - nearly half the total for that year - were thus caused or contributed to by navigational error or deficiency.   If navigation was such a problem less than half a century ago, it is scarcely surprising that the sea was such a frightening place when man went to sea for the first time.

Despite the lack of technical means at their disposal, the early navigators still managed to explore huge areas of oceans.  The Phoenicians explored not only the Mediterranean but also the eastern shores of the Atlantic and the western shores of the Indian Ocean.

Early Sea Voyages
Norsemen of ScandinaviaPerhaps the most remarkable were the Vikings or Norsemen of Scandinavia [4] (right), who not only visited (and terrorised) much of northern Europe, but also went to Russia and south to the Mediterranean. Perhaps their greatest achievement as seafarers was to cross the north Atlantic to Iceland, Greenland and finally to North America. What makes their voyages all the more remarkable was the fact that they did not even know these places were there.

Like other navigators before and after them, the Vikings made full use of available physical clues.  They discovered that ocean currents tend to flow in fixed directions, while winds generally blow for most of the time in set directions.  They also discovered that the planets and stars could be used for navigation.  The Vikings knew when they were approaching the Faeroe Islands by the way the water swelled over the banks surrounding the islands; and the abrupt change in water temperature told them they were close to Greenland.  They had a good understanding of tidal movements.  They noted the flight of birds, some of which may have been taken with the ship when it left port and then released at regular intervals: at first the bird would fly back home, later it would return to the ship, but as the ship neared land so the bird would fly ahead, enabling the ship’s crew to adjust their course and follow.   
At night they would look out for Polaris, the Pole Star, which always maintains a fixed position: navigators could determine its angle off the bow of the ship and use that to set a course.  By maintaining a steady 90-degree angle, for example, they could keep sailing along a fixed latitude.  This was especially useful since Iceland and Greenland were all roughly on the same latitude as Norway. 

During During the day, the Vikings could follow the course of the sun – much easier to do in northern latitudes than near the Equator, where the sun appears to be overhead for much longer. To help maintain their course, the Vikings probably also used a “sun-shadow board”, a semi-circle of wood, the rounded edge of which was divided by a series of notches.  By looking at the sun at noon, with the flat edge level with the horizon, the navigator could estimate how high the sun was in the sky.  This in turn showed how far north or south the ship was.  When the sky was overcast and the sun could not be seen, the Vikings used the mineral CordieriteCordierite (left) to show the direction of the sun under such condition. The pleochroic property of Cordierite, also sometimes called sun stone, absorbs the sun light in a certain direction (polarization) as it passes through the Cordierite “lens” making it possible to locate the position of the sun relative to the horizon.

In Oceania, the Polynesians of the southern Pacific were also demonstrating an astonishing ability to find their way across the oceans over 3,500 years ago.  By the time the Europeans entered the Pacific in the 16th century, virtually all the habitable islands had been settled for centuries.  The Polynesians navigated by using winds and currents and also knew of the significance of Polaris, the Pole Star.  They could estimate the canoe’s speed by noting how long it took bubbles to pass along the length of the craft.  The Polynesians were even able to build maritime charts, made of sticks, which could be used to identify islands, currents and other information. 

In Europe, seafarers estimated the ship’s speed by attaching a knotted line into the sea and then counting the number of knots that were paid out during a given time (the origin of the “knot”, which is still used as a measurement of speed at sea.) To estimate their speed and course, seafarers used a process known as dead reckoning. In dead reckoning, the navigator estimates a ship's position by keeping a careful record of its movement. The initial point of departure for dead reckoning is usually the last fix the navigator obtains at the start of a voyage. From this point, true courses steered and distances travelled are plotted on a chart. Points along the dead reckoning line, representing successive positions of the ship, are labelled with the appropriate time and the notation "D.R." The dead reckoning line on the chart is important to the navigator because it indicates at a glance the theoretical position of the ship, the track the ship should have followed, and the direction in which the ship is travelling.

Seafarers needed to know how deep the water was – to make sure the ship did not run aground – and this was generally done by throwing overboard a line to which a lead weight was attached. The line would be divided into set distances by knots and the bottom of the weight would be covered in tallow which would pick up samples of the seabed: with some experience, this could also be used to assist in determining the ship’s position. The Greek historian Herodotus wrote in the fourth century BC: “When you get 11 fathoms and ooze on the lead, you are a day’s journey from Alexandria.

The early navigators, such as the Vikings and Polynesians, were remarkably successful, yet their success was limited. The Vikings certainly reached North America centuries ahead of Columbus, but they did not establish a permanent foothold, partly because of lack of numbers and also because the climate turned against them. By about 1400 even the settlements in Greenland were in decline.  In the Pacific, the islands were too small to enable large settlements to be created.  In the absence of a strong literary tradition, it was also difficult for both Vikings and Polynesians to pass on and so to accumulate knowledge. 

zhengheUntil the emergence of the Vikings, maritime supremacy in the West had always been based on the Mediterranean.  The Egyptians, Greeks, Phoenicians, Romans and others had all been dominant powers in antiquity, but with the exception of the Phoenicians, their power was based on military rather than naval strength.  Because the Mediterranean is almost totally enclosed, virtually tideless and relatively small in area, there was no real incentive to improve the technology of seafaring.  Armies, not fleets, won wars.  But by the 15th century, the balance of power had switched from the Mediterranean areas to the nations situated on the western edge of the continent – Portugal, Spain, France, England and the Netherlands. 

Outside of Europe, there was relatively little interest in the sea. The Chinese did for a period show great interest in military expansion in Southeast Asia, but it was brought to an abrupt end in the 1490s due to the political situation in China.  However, trading continued even after the fall of the Ming Dynasty in 1644 and through to the Qing Dynasty.  On the other hand, the Arabs who led the world in such sciences as mathematics, medicine and astronomy, did show an interest in the sea, but they were primarily concerned with the land, especially in trade and spreading Islam.

In the 15th century, first the Portuguese and then the Spanish embarked on what was to become known as the age of exploration. Within four centuries, the coastline of the whole world was known and most of the interior also explored.

Charting the Seas
click here to enlargeOne of the most important and basic of all navigational aids was the marine chart.  Some of the earliest also known as portolan charts, were produced in Italy during the Renaissance, the earliest surviving one being the Carte Pisane, which was probably made in Genoa in 1290.  Like other portolan charts, the actual depiction of the coastline was inaccurate.  What portolan charts did was to provide basic information about distances and coastal features which could be used by seafarers to recognize where they were – and how to continue on their voyage. 

History of Cartography
Christopher columbus

Early attempts to develop charts that could be used for navigation, which included the initial task of surveying the coastline inevitably resulted in distortion, and none of the maps produced could be described as accurate and none of them could really be used for plotting a course.  This was partly because of the difficulty of converting a sphere into a flat surface such as a chart.  It was also impossible to produce accurate maps until the surface of the world had been properly surveyed, a process that was to take centuries of painstaking work.
The first great explorers of the early modern period were the Portuguese, who reached the Azores and Madeira in the 1430s.  In 1487, Bartoloméo Diaz rounded the Cape of Good Hope to become the first European to enter the Indian Ocean from the south and in 1498, Vasco de Gama used the same route to reach India. 

click here for the biographyIn 1492, Christopher Columbus (Left) crossed the Atlantic and reached the islands of the Caribbean.  It is an indication of the lack of knowledge that existed at the time that Columbus was convinced that he had reached Asia.  Like others at the time, he had no real idea of the size of the world and was unaware that Americas even existed.  However, the European voyages of the 15th and 16th centuries helped to establish the basic shape of the world and also confirmed that it was round and not flat and that it revolves around the sun, like other planets.  In 1519, Ferdinand Magellan (Right) set sail from Spain with five ships and although he was himself killed in a skirmish in the Philippines, one ship Victoria(Left) piloted by Sebastian del Cano managed to get back to Spain in 1522, and became the first ship to circumnavigate the world.

Click here to see Map of the world and route taken by Ferdinand Magellan

VictoriaThe invention of the telescope at around the same time helped to revolutionise understanding of astronomy and shatter most of the superstitions that had stood in the way of science for so long.  Having identified the basic shape of the world and most of its land masses (Australasia and Antarctica were still unknown to the Europeans), the next step was to map it. 

Cartography was not new.  For centuries, man had been trying to represent the shape of the earth.  For seafarers, the most important requirement was not to create an accurate shape but to find a projection that would enable a course to be plotted on a flat surface.  The most successful attempt was that of Gerardus Mercator in 1569.  His projection makes line of latitude and longitude intersect at right angles.  The direction of travel – the thumb line – appears as a straight line, rather than as a curve.

The Mercator projection was ideal for navigators, although it did not become standard for some decades.  By the 17th century, it had become widely used and is still used in maritime charts.  Its major disadvantage is that it greatly distorts land size (Greenland, for example, appears to be large than Africa when in fact it is smaller than the Arabian peninsular). 

The Mercator projection was a major contribution to the art of seafaring, but over the centuries numerous scientific instruments were also added to the navigator’s armoury.  Of these, the most important was the magnetic compass, which originated in China and was introduced to Europe by Arab traders around about the 12th century.

Magnetic compasses work because the earth acts as a giant magnetic field, which causes the compass – a needle of iron – to align itself in a north-south direction.  To do this, the iron needle had to be “magnetised” by means of a lodestone, a mineral called magnetite.  The ability to find north and south – and hence all other points of the compass - without having to look at the stars or the sun was an obvious boon to European navigators, especially when the sky was overcast.  Nevertheless, the magnetic compass has some disadvantages.  For one thing, the compass points not to true north but to magnetic north, which is some distance away (it varies from place to place).  To give an accurate reading, the compass also has to be on a flat surface: yet the bridge of a ship is frequently battered by waves and the wind.  To overcome this problem, compasses were “gimbal-mounted”, a device which enabled the motion of the ship to be neutralised.  The development of iron ships in the 19th century added another problem, since the compass could be affected by iron. 

astrolabFinding the ship’s position was, however, another problem.  To help determine latitude, the Greeks invented the astrolabe (left), basically a map of the skies.  Originally it was used to show how the sky looks at a particular time, as well as by astrologers to help determine horoscopes.  The astrolabe was not really suitable for use on board  a ship at sea because of the way the ship continually moves with the waves.  However, the basic idea of using instruments to make celestial observations and measurements to help determine a ship’s position led to the development of numerous devices, one of the earliest being the quadrant, a quarter of a circle used to measure the altitude of a star or other heavenly body.  The quadrant, which could only measure angles of up to 90 degrees, was later replaced by the sextant, which could measure angles of up to 120 degrees.  It enabled lunar observations to be made to establish a ship’s longitude. 

Other important navigational instruments included the cross-staff, which was used for measuring the angle of the sun or Pole star and the back-staff, which was invented in 1594 to overcome the problems encountered by staring into the sun when using a cross-staff.  With the exception of the compass, however, the greatest contribution made to maritime navigation was the invention of the marine chronometer, enabling mariners to establish longitude.  The Portuguese and other explorers could fix their latitude but they generally had only a hazy idea of their longitude – which is why Columbus thought he had reached Asia when in fact he had only arrived in America. 

The Portuguese, Spanish and others all tried to solve the problem by astronomical means, but failed to do so.  In theory, the solution should have been relatively simple.  It was known that for every 15 degrees that one travels east, the local time advances by an hour.  By knowing the local time at two points it should be possible to calculate the distance between two points – such as the ship and the port of departure.  The problem was building a clock that could keep accurate time while withstanding the motions of the ship and the great changes in heat and humidity that were likely to be encountered on a long voyage.  

Latitude and Longitude

chronometersIn 1714, the British Government offered a prize of £20,000 – a huge sum at the time –for the person who could provide longitude to within half a degree (two minutes in time).  The problem was eventually solved by a joiner from Yorkshire named John Harrison, who built five chronometers (left)[3], the last two of which more than met the strict requirements laid down by the Board of Longitude.  However, the Board stubbornly refused to recognize Harrison’s achievement and it took an act of parliament to do so.  A more practical proof of Harrison’s work came when Captain Cook took a copy of H4 on his second voyage and later referred to it as “our faithful guide through all the vicissitudes of climate.”

By the beginning of the 19th century, most of the early navigational problems had been solved.  The shape of the world was known and seafarers could find their way and work out their position with considerable accuracy.  The technical innovations of the industrial revolution helped many navigational aids to be improved and others to be developed.  The patent log, for example, was introduced in the 19th century to measure a ship’s speed.  The gyroscopic compass was invented at the end of the century and overcame most of the problems associated with the earlier magnetic device. 

Early Measures on Navigational Safety
Despite the advances in navigational aid, especially in the 19th century, there were still serious question marks over navigational techniques and especially over navigational safety.  Although the basic principles concerning route finding were understood, there was no general agreement on more local issued – such as avoiding collisions.  Rules to prevent collisions at sea have existed for several hundred years, but they had no statutory force until 1840, when the London Trinity House drew up regulations that were enacted by the British parliament in 1846.  By then, the British merchant marine was so dominant in world shipping that action taken by the British government – especially in matters such as safety – was generally welcomed and frequently followed by other nations.  The fact that steam ships were becoming more common also meant that the time was ripe for some form of international agreement on safety issues: it was difficult to legislate for ships that were to some extent at the mercy of the elements, but powered ships had much greater control over their actions.

One of the new regulations required a steam vessel passing another vessel in a narrow channel to leave the other on her own port hand. Another required steam vessels on different courses, crossing so as to involve risk of collision, to alter course to starboard so as to pass on the port side of each other.  There were also regulations for vessels under sail, including a rule, established in the 18th century, requiring a sailing vessel on the port track to give way to a sailing vessel on the starboard track.

The two Trinity House rules for steam vessels were combined into a single rule and were incorporated into the Steam Navigation Act of 1846.  Admiralty regulations concerning lights were included in this statute two years later.  Steam ships were required to carry green and red sidelights as well as a white masthead light.  In 1858, coloured sidelights were prescribed for sailing vessels and fog signals were required to be given, by steam vessels on the whistle and by sailing vessels on the fog horn or bell.

A completely new set of rules drawn up by the British Board of Trade in consultation with the French government came into operation in 1863.  By the end of 1864, these regulations, known as "Articles", had been adopted by more than 30 maritime countries including the United States and Germany.

Several important regulations - which are still essentially in force today - were introduced at that time.  To avoid the risk of collision when steam vessels were crossing, the vessel with the other on her own starboard side was required to keep out of the way.  Steam vessels meeting end-on or nearly end-on were required to alter course to starboard.  Every vessel overtaking any other had to keep out of the way of the vessel being overtaken.  Where, by any of the rules, one vessel was to keep out of the way, the other was required to keep her course.

Some changes to the 1863 rules came into force in 1880, including a new rules permitting whistle signals to be given to indicate actions taken by steam ships to avoid collision.  In 1884 a new set of regulations came into force, but they were not substantially different.

The first International Maritime Conference to consider regulations for preventing collisions at sea was held in Washington in 1889.  Among the new provisions agreed at the Conference were requirements that a stand-on vessel should keep her speed as well as her course, that a giving-way vessel should avoid crossing ahead of the other vessel and that steamships should be permitted to carry a second white masthead light.  The regulations were brought into force by several countries in 1897.  At a Maritime Conference held in Brussels in 1910, international agreement was reached on a set of regulations similar to those drafted in Washington and these remained in force until 1954.

Titanic source 1912 Titanic disaster resulted in a major international conference in London in 1914, which adopted the first International Convention for the Safety of Life at Sea (SOLAS).  It introduced new international requirements dealing with safety of navigation for all merchant ships; the provision of watertight and fire-resistant bulkheads; life-saving appliances; and fire prevention and fire fighting appliances on passenger ships.  Other requirements dealt with the carriage of radiotelegraph equipment for ships carrying more than 50 persons (had the Titanic's distress messages not been picked up by other ships, the loss of life would probably have been even greater); the Conference also agreed on the establishment of a North Atlantic ice patrol.  The Convention was to enter into force in July 1915, but by then the First World War had broken out in Europe and it never did so, although many of its provisions were adopted by individual nations.

In 1929, another conference was held which adopted a revised SOLAS Convention.  By 1948, the regulations were again in need of revision and a revised treaty was adopted.  At another conference held that year, a convention establishing the International Maritime Organization (then known as Inter-Governmental Maritime Consultative Organisation) was adopted.  It entered into force ten years later and for the first time, the shipping community has a permanent body to consider matters of mutual interest.  One of its first tasks was to convene a new conference in 1960 to adopt a new SOLAS convention and also to consider new collision regulations.

The creation of IMO came at the right time, because shipping, like many other industries, had become global and needed to be regulated at the international rather than the industry or national level.  Although the 1889 Washington Conference represented the first major attempt to establish an international system for regulating shipping safety, it was unfortunately ahead of its time and relatively little was achieved.  Experience was to show that change usually needed a disaster – such as the Titanic – to provide the necessary impetus.

Experience also showed that there were many aspects of navigation that needed attention at the international level quite apart from regulations to prevent collisions at sea.  They included buoyage systems and lighthouses.  The beginnings of a unified system of buoy marking emerged in 1889, but it was not until 1936 that a worldwide unified system was agreed upon at the League of Nations in Geneva.  The Second World War began before the agreement could be fully ratified, and in the aftermath of the war, little progress was made.  At one time there were nine different systems in use.  By 1973, however, a number of spectacular marine accidents urged the international community into action, and by 1980, a new unified system had been agreed upon by 50 maritime countries that were members of the International Association of Lighthouse Authorities.  The system applies two nearly identical standards to two regions.  Region A comprises Europe, Australia, New Zealand, Africa, the Persian Gulf, and most Asian states.  Region B includes the Americas, Japan, Korea, and the Philippines. 

The impact of technology

tankerThe Second World War made a major impact on the technology of shipping and many of the inventions originally developed for military purposes were later to have a huge – and beneficial impact on shipping safety.  These developments came just in time, because shipping itself was undergoing dramatic changes that soon made it clear that the traditions and techniques that had been developed over the centuries were no longer adequate.

Inventions such as radar and improvements in communications offered great opportunities, while the changes in shipping which took place in the 1960s - such as the development of ships with a draught much greater than anything known before - made it clear that treaties such as SOLAS and the collision regulations would have to be further amended.   The new technology also implied that traditional attitudes would also have to change.  For centuries, the ship’s captain had been in almost every sense the master and his decision was final.  By the end of the 20th century, the independence and hence the authority of the master was being challenged, because for the first time, those on shore often had a better idea of what was happening than those at sea.  It followed that in future, ships would increasingly have to obey rules imposed by those on shore.
An indication of what lay ahead came in 1972 when an international conference to amend the International Regulations for Preventing Collisions at Sea was held; the new Convention (known as the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs)) was adopted on 20 October 1972 and entered into force on 15 July 1977.  

One of the most important changes attributed to COLREGs was to make possible the introduction of mandatory ships’ routeing systems.  The practice of following predetermined routes for shipping originated in 1898 and was adopted, for reasons of safety, by shipping companies operating passenger ships across the North Atlantic.   Related provisions were subsequently incorporated into the original SOLAS Convention

Ships Routeing Systems

The 1960 SOLAS Convention referred to ships' routeing measures in busy areas on both sides of the North Atlantic.  Contracting Governments undertook the responsibility of using their influence to induce the owners of all ships crossing the Atlantic Ocean to follow the recognized routes and to ensure adherence to such routes in converging areas by all ships, so far as circumstances permitted.  Meanwhile, analysis of casualty statistics was showing that collisions between ships were becoming a worrying cause of accidents, especially in congested waterways.
tankerIn 1963, the Liverpool Underwriters Association reported 21 collisions responsible for total losses of ships - compared with a five-year average of 13.8.  A report on tanker hazards presented to the United States Treasury presented in late 1963 concluded that most accidents were due to human error, with speed in congested waters a principal cause.  The report said that there were too many diverse "rules of the road", the width of navigable channels had generally not kept pace with the increase in sizes of ships, and not enough was being done to use modern communications.  At the same time, the institutes of Navigation of the Federal Republic of Germany, France and the United Kingdom had begun a study on improving safety measures in congested areas, such as the English Channel.   The group came up with a series of proposals, including the idea that ships using congested areas should follow a system of one-way traffic schemes, like those being used on land.  Traffic lanes of this type were already in use on the Great Lakes of North America. 

The proposals were favourably received by the Maritime Safety Committee of IMO in 1964 and governments were urged to advise their ships to follow the routes suggested by the group.  In 1966, the institutes published a report proposing traffic separation schemes in a number of areas, and in June 1967, a traffic separation scheme was established in the Dover Straits - and a significant fall was seen in the number of collisions between ships on opposing courses.  At that time, observance of the schemes was voluntary, but in 1971, a series of accidents in the English Channel led to calls for immediate action - in the most serious incidents, the tanker Texaco Caribbean was in collision with a freighter off the Varne shoals and the following night, the wreck was struck by the freighter Brandenburg, which also sank.  Some six weeks later, the freighter Niki struck the wreckage and sank with the loss of all 21 people on board.  As a result, IMO's made the observance of traffic separation schemes mandatory later the same year.  The Conference that adopted the Collision Regulations (COLREGs), in 1972 also made observance of traffic separation schemes mandatory.  IMO's responsibility for ships’ routeing is also enshrined in SOLAS Chapter V, regulation 8, which  recognizes the Organization as the only international body for establishing such systems, while Rule 10 of the COLREGs prescribes the conduct of vessels when navigating through traffic separation schemes adopted by IMO.  IMO's responsibilities are also determined under the 1982 United Nations Convention on Law of the Sea (UNCLOS), which designates IMO as "the competent international organization" in matters of navigational safety, safety of shipping traffic and marine environment protection.

In 1977, the Assembly authorized the Maritime Safety Committee to adopt traffic separation schemes on the Organization's behalf, in order to speed up the procedure[1] [2].
As well as traffic separation schemes, other routeing measures adopted by IMO to improve safety at sea include two-way routes, recommended tracks, deep water routes (for the benefit primarily of ships whose ability to manoeuvre is constrained by their draught), precautionary areas (where ships must navigate with particular caution), and areas to be avoided (for reasons of exceptional danger or especially sensitive ecological and environmental factors).

Ships' routeing systems and traffic separation schemes that have been approved by IMO, are contained in the IMO Publication, Ships' Routeing.  The publication includes General provisions on ships' routeing, first adopted by IMO in 1973, and subsequently amended over the years, which are aimed at standardizing the design, development, charted presentation and use of routeing measures that have been adopted by IMO.  The provisions state that the objective of ships' routeing is to "improve the safety of navigation in converging areas and in areas where the density of traffic is great or where freedom of movement of shipping is inhibited by restricted searoom, the existence of obstructions to navigation, limited depths or unfavourable meteorological conditions".

Elements used in traffic routeing systems


Traffic separation scheme:  a routeing measure aimed at the separation of opposing streams of traffic by appropriate means and by the establishment of traffic lanes

Traffic lane: an areas within defined limits in which one-way traffic is established.  Natural obstacles, including those forming separation zones, may constitute a boundary

Separation zone or line: a zone or line separating traffic lanes in which ships are proceeding in opposite or nearly opposite directions; or separating a traffic lane from the adjacent sea area; or separating traffic lanes designated for particular classes of ship proceeding in the same direction

Roundabout: a separation point or circular separation zone and a circular traffic lane within defined limits.

Inshore traffic zone: a designated area between the landward boundary of a traffic separation scheme and the adjacent coast

Recommended route: a route of undefined width, for the convenience of ships in transit, which is often marked by centreline buoys

Deep-water route: a route within defined limits which has been accurately surveyed for clearance of sea bottom and submerged articles

Precautionary area: an area within defined limits where ships must navigate with particular caution and within which the direction of flow of traffic may be recommended

Area to be avoided: an area within defined limits in which either navigation is particularly hazardous or it is exceptionally important to avoid casualties and which should be avoided by all ships, or by certain classes of ships

Traffic separation schemes and other ship routeing systems have now been established in most of the major congested, shipping areas of the world, and the number of collisions and groundings has dramatically reduced. 

Weather conditions can also affect a ship's navigation, and in 1983, IMO adopted resolution A.528 (13), Recommendation on Weather Routeing, which recognizes that weather routeing - by which ships are provided with "optimum routes" to avoid bad weather - can aid safety.  It recommends Governments to advise ships flying their flags of the availability of weather routeing information, particularly that of services listed by the World Meteorological Organization.

Vessel Traffic Services

click here to enlargeTraffic separation schemes and other ships' routeing systems may be combined with a vessel traffic service (VTS), which is defined as a service designed to improve the safety and efficiency of vessel traffic and to protect the environment. VTS (right) may range from the provision of simple information messages to ships navigating in certain areas, such as position of other traffic or meteorological hazard warnings, to extensive management of traffic within a port or waterway.

Generally, ships entering a VTS area report to the authorities, usually by radio, and may be tracked by the VTS control centre.  Ships must keep watch on a specific frequency for navigational or other warnings, while they may be contacted directly by the VTS operator if there is risk of an incident or, in areas where traffic flow is regulated, to be given advice on when to proceed.  Traditionally, the master of a ship has been responsible for a ship's course and speed, assisted by a pilot where necessary.  Ships approaching a port would announce their arrival using flag signals.  With the development of radio in the late 19th century, radio contact became more important. 

But the development of radar during the Second World War made it possible to accurately monitor and track shipping traffic.  The world's first harbour surveillance radar was inaugurated in Liverpool, England, in July 1948 and in March 1950, the first radar surveillance system in the United States was established at Long Beach, California.  The ability of the coastal authority to keep track of shipping traffic by radar, combined with the facility to transmit messages concerning navigation to those ships by radio, therefore constituted the first formal VTS systems.

IMO Publication, Ships' RouteingThe value of VTS in navigation safety was first recognized by IMO in resolution A.158 (ES.IV) Recommendation on Port Advisory Systems adopted in 1968, but as technology advanced and the equipment to track and monitor shipping traffic became more sophisticated, it was clear that guidelines on standardising procedures in setting up VTS were needed.   In particular, it became apparent that there was a need to clarify when a VTS might be established and to allay fears in some quarters that a VTS might impinge on the ship's master's responsibility for navigating the vessel.  As a result, in 1985, IMO adopted resolution A.578 (14) Guidelines for Vessel Traffic Services, which states that VTS was particularly appropriate in the approaches and access channels of a port and in areas having high traffic density, movements of noxious or dangerous cargoes, navigational difficulties, narrow channels, or environmental sensitivity.  The Guidelines also made clear that decisions concerning effective navigation and manoeuvring of the vessel remained with the ship's master.

The Guidelines also highlighted the importance of pilotage in a VTS and reporting procedures for ships passing through an area where a VTS operates.  Revised Guidelines for vessel traffic services, including Guidelines on Recruitment, Qualifications and Training of VTS Operators, were adopted as IMO Assembly resolution A.857 (20) in November 1997.  The Guidelines update and expand on the now revoked resolution A.578 (14) and is associated with a new SOLAS regulation V/8-2 on VTS.

Vessel Traffic Services were not specifically referred to in the 1974 SOLAS, but in June 1997, IMO's Maritime Safety Committee adopted a new regulation 8-2 to Chapter V (Safety of Navigation), which sets out when VTS can be implemented.  The regulation states that VTS contribute to the safety of life at sea, safety and efficiency of navigation and the protection of the marine environment, adjacent shore areas, worksites and offshore installations from possible adverse effects of maritime traffic. Governments may establish VTS when, in their opinion, the volume of traffic or the degree of risk justifies such services.  But no VTS should prejudice the "rights and duties of governments under international law" and a VTS may only be made mandatory in sea areas within a State's territorial waters.  The regulation entered into force on 1 July 1999. 

Ship Reporting Systems

Electronic RadarIn some parts of the world, ships should report to the coastal authorities so that they can keep track, via radar and radio, of ships in the area and respond quickly if there is an emergency.  Ship reporting systems (SRSs) are therefore used to gather or exchange information about ships, such as their position, course, speed and type of cargo carried.  The data may be used for search and rescue, vessel traffic services and prevention of marine pollution.

With the development of traffic separation schemes and vessel traffic services in busy shipping areas around the world from the 1970s, it soon became clear there was a need to develop a standardised ship reporting format.  This was recognised at the IMO’s Search and Rescue Conference in Hamburg in 1979, which adopted a resolution calling on IMO to develop standardised reporting procedures for SRSs.

As a result, IMO adopted General Principles for Ship Reporting Systems in 1983, which noted that various national systems in place at the time used different procedures and reporting formats, which could cause confusion to masters and ships moving from one area to another.  The resolution, therefore, included in an annex a standardised format and procedures for ship reporting.  The resolution stressed that reports should be simple and to use the standard international ship reporting format and procedures.  Where language difficulties exist, the language used should be English, using where possible Standard Marine Navigational Vocabulary.  The reporting system should allow for special reports from ships concerning defects or deficiencies with respect to their hull, machinery, equipment or manning, or concerning other limitations which could adversely affect navigation and for special reports concerning marine pollution.  Basic information such as ship's particulars should only be reported once and be retained in the system and updated only when changes on the basic information were reported.  The resolution was updated in 1987, by resolution A.598 (15), to include guidelines for reporting incidents involving harmful substances and dangerous goods, as recommended by the Marine Environment Protection Committee. 

The ship reporting Guidelines were revised again in 1989, by resolution A.648 (16), where the guidelines were expanded and named General principles for ship reporting systems and ship reporting requirements, including guidelines for reporting incidents involving dangerous goods, harmful substances and/or marine pollutants.  The resolution also makes reference to the need for coastal states to be informed by master of an assisting ship, or a ship undertaking salvage, on particulars of an incident. 

In different ship reporting systems, ships may be requested to provide more or fewer details, depending on the needs of the system.  Until the mid-1990s, reporting systems had been voluntary, or recommended.  In 1994, however, IMO adopted an amendment to SOLAS making it possible to introduce mandatory reporting systems.
Regulation 8-1 to SOLAS Chapter V: Ship reporting systems, entered into force on 1 January 1996. The regulation states that SRSs contribute to safety of life at sea, the safety and efficiency of navigation and the protection of the marine environment. Ships are required to comply with the provisions of ship reporting systems developed in accordance with IMO guidelines and recognized by IMO. 

SOLAS Chapter V Regulation 8-1 refers in a footnote to the General principles for ship reporting systems described earlier, and to MSC resolution MSC.43 (64) Guidelines and criteria for ship reporting systems, which highlights the procedures and considerations Governments should follow in proposing mandatory ship reporting systems for adoption by IMO.  In particular, the Guidelines note that ship reporting systems should be considered for adoption only if supported by a "demonstrated need" to address one or more of: the improvement of safety of life at sea, the safety and efficiency of navigation, and/or to increase the protection of the marine environment.  In addition, communication between a shore-based authority and a participating ship should "be limited to information essential to achieve the objectives of the system".  These criteria reflect the tradition in shipping of freedom of navigation and free passage, while accepting that imposing stricter controls on ships' movements in congested waters or environmentally sensitive areas can help reduce accidents involving loss of live or pollution.

Automatic ship reporting systems

automatic identification systemsDevelopments in technology mean that it is now feasible for ships entering a ship reporting area to automatically report in their position, speed and other details via VHF radio.  It also means that the operators of a ship reporting system (the coastal State) can easily track the ships' movements without necessarily having to communicate directly with the ship, unless there is a specific need to do so. Such a system would have automatic warning systems, so alerts would be given in the case of an incident or impending incident.  The Guidelines and Criteria for ship reporting systems note the possibility of automated ship reporting, pointing out that: "Shore-based authorities should remain alert to the development of non-verbal methods of data transfer which may reduce language difficulties and that have great potential for reducing ships' reporting burden".

IMO's Maritime Safety Committee meeting adopted performance standards for automatic ship reporting systems in May 1998.  The draft standards state that automatic identification systems (AIS) (right) are designed to provide information from the ship to ships and to coastal authorities, automatically, continuously and with the required accuracy and frequency.  AIS should operate in ship-to-ship mode for collision avoidance; ship-to-shore mode for coastal States to obtain information about a ship and its cargo; and as a tool in VTS for traffic management.

The advantage of AIS is that ships can be alerted to the presence of other ships, and coastal authorities can pinpoint the position of ships, which even with radar this would be impossible, because of landforms in the way, or because the radar signals would need to travel around a corner.
Navigation systems

The introduction of radio and wireless technology in the late 19th century permitted the development of more sophisticated navigation systems.  Wireless time signals, which were first broadcast from Paris in 1910, enabled more accurate determination of longitude, while the Italians Ettore Bellini and Captain Tosi in 1906 developed a direction finding system used to determine the direction from which wireless signals were transmitted.
After the end of the Second World War, the development of radar led to the possibility of ships being able to fix their position, when within 48 to 60 miles of the shore, by making reference to coastal features or responder beacons (Racons) installed on the shore.  Further out to sea, hyperbolic radio systems soon enabled accurate position fixing with a range of at least 250 miles.

Decca NavigatorThese early radio navigation systems - including Decca Navigator (right) and Loran A - involved a ship's radio receiver measuring transmissions from groups of radio transmitters transmitting signals simultaneously or in a controlled sequence.  By measuring the phase difference between one pair of transmissions, a position line can be established.  A second measurement from another pair of stations gives a second line and the intersection of the two lines gives the navigating position.  

By the 1970s, Loran C and Differential Omega radio navigation systems were also entered into service in major areas of the world's oceans and they were combined with early computer technology to provide electronic print outs of the ship's position.  The Soviet Chayka system also became operational.

In the 1960s, however, the successful introduction of the world's first satellites was to dramatically alter communications at sea and ultimately to transform navigation.   By the late 1960s, IMO begun consideration of the establishment of an organization devoted to using satellite technology for maritime purposes.  At that time, one of the problems with communications at sea is that it is impossible to connect a ship to a conventional telephone system.  It is possible to use radio, but radio waves go in straight lines and eventually go off into space.  Satellites enabled this problem to be overcome.  A message can be sent from a ship to shore (or vice-versa) via a geostationary satellite.  This work culminated, in 1976, with the establishment of the International Maritime Satellite Organization (INMARSAT), an international organization dedicated to providing a modern communications system for shipping.  It was designed chiefly to improve distress and safety communications.

IMO and navigation systems

The importance of using navigation systems in maritime safety and preventing marine pollution, for example as an aid to avoiding hazards, was recognized by IMO in the late 1960s, which let to the adoption of resolution A.156 (ES.IV) on Recommendation on the Carriage of Electronic Position-Fixing Equipment in 1968.  The resolution recommended that ships carrying oil or other noxious or hazardous cargoes in bulk should carry "an efficient electronic position-fixing device". 

Performance Standards for Shipborne Receivers for use with Differential Omega (resolution A.479 (XII) were adopted in 1981, while in 1983 the Assembly adopted resolution A.529 (13) on Accuracy Standards for Navigation.  Resolution A.529 (13) is aimed at providing "guidance to Administrations on the standards of navigation accuracy for assessing position-fixing systems, in particular radio-navigation systems, including satellite systems".  It notes that "the navigator needs to be able to determine his position at all times". 

Accuracy of navigation systems in areas such as harbour entrances and approaches depends on local circumstances, but in other waters, the resolution established that navigation systems should provide accuracy within the order of 4% of the distance from danger with a maximum of 4 nautical miles (for a ship proceeding at not more than 30 knots). 

Also in 1983, IMO began a study into a world-wide radio-navigation system, in view of the need for such a system to provide ships with navigational position-fixing throughout the world -  but recognizing that it was not considered feasible for IMO to fund a world-wide radio-navigation system.

The objective of the study was to provide a basis by which Regulation 12 (covering shipborne navigational equipment) of SOLAS Chapter V might be amended to include a requirement for ships to carry equipment to receive transmissions from a radio navigation system throughout their intended voyage.

SOLAS Chapter V Regulation 12 includes a requirement for ships on international voyages over 1,600 gross tonnage to be fitted with radio direction-finding apparatus which dates back to the 1948 SOLAS Convention.  In 1988, IMO adopted an amendment that allowed ships the possibility to carry instead radionavigation equipment suitable for use throughout the intended voyage.

World-wide radio navigation system

bridge systemIn 1985, IMO initiated a study into a world-wide satellite position-fixing system for the safety of navigation and a report, Study of a World-Wide Radionavigation System, was adopted by the IMO Assembly in 1989 (resolution A.666 (16).  The report gave a detailed summary of the different terrestrial-based radio navigation systems then in operation (Differential Omega, Loran-C, Chayka), and also the satellite systems which were being developed - Global Positioning System (GPS) Standard Positioning Service (SPS), which was being developed by the United States air force; and GLONASS (Global Navigation Satellite System), being developed by the then Soviet military (now managed for the Government of the Russian Federation by the Russian Space Agency).

The 1989 report stated that it was not considered feasible for IMO to fund a world-wide radionavigation system, so existing and planned systems provided and operated by Governments or organizations were studied to ascertain whether they could be recognized or accepted by IMO.


A very low frequency (VLF) hyperbolic radionavigation system based on phase comparison techniques, which ceased operations in September 1997.  Omega evolved from a low frequency system known as Radux, first proposed in 1947 and was further developed in the 1950s, was the first world-wide radio-navigation system offering global coverage.  Eight Omega stations are in operation and located in Norway, Liberia, Hawaii, North Dakota, La Reunion, Argentina, Australia and Japan.  Differential Omega refers to the provision of increased accuracy in a local area, such as a harbour, through the use of local transmitters of the Omega signal. 

When a radio-navigation system is accepted by IMO, it means the system is regarded as capable of providing adequate position information and that the carriage of receiving equipment satisfies the relevant SOLAS requirements.

The report notes that shipborne receiving equipment should conform to the general requirements for navigational equipment in resolution A.574 (14) (later updated by A.694 (17) and that detailed requirements for receivers for GPS, differential GPS, GLONASS, differential GLONASS, Loran-C, Chayka, Omega combined with differential Omega and Decca Navigator systems were available to manufacturers to enable them to construct the equipment.


Chayka radionavigation system, similar to LORAN-C, operated by the Russian Federation. Accuracy is 50 to 200 nautical miles.

The 1989 report set operational requirements for world‑wide radionavigation systems, i.e., it should be general in nature and be capable of being met by a number of systems.  All systems should be capable of being used by an unlimited number of ships.  Accuracy should at least comply with the standards set out in resolution A.529 (13) Accuracy of Standards for Navigation 

The report was updated in 1995 by resolution A.815 (19), World-Wide Radionavigation system, which takes into account the requirements for general navigation of ships engaged on international voyages anywhere in the world, as well as the requirements of the Global Maritime Distress and Safety System (GMDSS) for the provision of position information.

The revised report also addresses the development of high speed craft, such as fast ferries, noting that ships operating at speeds above 30 knots may need more stringent requirements.  The report further states that provision of a radionavigation system is the responsibility of governments or organizations concerned and that these should inform IMO that the system is operational and available for use by merchant shipping while keeping IMO informed in good time of any changes that could affect the performance of shipborne receiving equipment. 

Updated performance standards for Decca Navigator and Loran-C and Chayka receivers and performance standards for shipborne global positioning system (GPS) receiver equipment were also adopted in 1995.  By then, GPS was fully operational, while GLONASS became fully operational in 1996.

Global Positioning System (GPS)

GPS towerThe Global Positioning System (GPS) Standard Positioning Service (SPS) is a space-based three dimensional positioning velocity and time system which is operated by the United States Air Force.  GPS met full operational capability in 1995.

The GPS is expected to be available for the foreseeable future, on a continuous, world-wide basis and free of direct user fees.  The United States expects to be able to provide at least six years notice prior to termination of GPS operation or elimination of the GPS.  This service, which will be available on a non-discriminatory basis to all users, meets the requirements for general navigation with a horizontal position accuracy of 100 meters (95%).

GPS has been recognized as a component of the World-Wide Radionavigation System (WWRNS) for navigational use.  But without augmentation, GPS accuracy is not suitable for navigation in harbour entrances and approaches or restricted waters.  GPS does not provide instantaneous warning of system malfunction.  However, differential corrections (DGPS) using maritime radiobeacons can enhance positional accuracy ranging from ± 5 m to sub-meter depending on the type of receiver used as well as also offer integrity monitoring.  Integrity provision may be possible by receiver autonomous integrity monitoring (RAIM)

Future global navigation satellite system

Maritime policy for a future global navigation satellite system (GNSS) sets out IMO policy in terms of the maritime requirements for a future civil and internationally-controlled Global Navigation Satellite System (GNSS), to provide ships with navigational position-fixing throughout the world for general navigation, including navigation in harbour entrances and approaches and other waters in which navigation is restricted.

The policy paper notes that development of a future GNSS is presently in a design stage and these requirements have been limited only to basic user requirements, without specifying the organizational structure, system architecture or parameters.  These maritime requirements, as well as the Organization's recognition procedures, may need to be revised as a result of any subsequent developments.

The paper also sets out the general, operational and institutional requirements for a future GNSS in terms of maritime users and envisages a review of the requirements in 1999 (21st Assembly); consideration of the proposed future GNSS in 2001 (22nd Assembly) and completion of the implementation of the proposed GNSS in 2008. 

The policy paper notes the following general requirements for the future GNSS:

1. It should primarily serve the operational user requirements for navigation.  For maritime use this includes navigation in harbour entrances and approaches, and other waters in which navigation is restricted;

2. It should have the operational and institutional capability to meet additional area-specific requirements through local augmentation, if this capability is not otherwise provided.  Augmentation provisions should be harmonized world-wide to avoid the necessity of carrying more than one shipborne receiver or other devices; and

3. It should have the operational and institutional capability to be used by an unlimited number of multi-modal users at sea, in the air and on land.

Navigational charts

Navigational chartUnder SOLAS Chapter V (Regulation 20), all ships are required to carry "adequate and up-to-date charts". 
In 1983, IMO adopted resolution A.532 (13), which referred to the importance of the provision of accurate and up-to-date hydrographic information to safety of navigation and to the fact that many areas had not been surveyed to modern standards.   The resolution invited Governments to conduct hydrographic surveys and co-operate with other Governments where necessary.

This was followed in 1985 by resolution A.580 (14) urging IMO Member Governments to establish regional hydrographic commissions or charting groups and to support groups already set up by the International Hydrographic Organization (IHO) to prepare accurate charts.  The resolution was adopted after representation from the IHO, which informed IMO of the inadequacy of nautical charts of many sea areas as a result of dependence on old hydrographic surveys and noted that substantial technical co-operation would be required between developed and developing coastal states on a regional basis to remedy this.

Meanwhile, many Member States are in favour of an amendment to SOLAS Chapter V which would put the onus on Contracting Governments to arrange for the collection and compilation of hydrographic data and the publication, dissemination and keeping up to date of all nautical information necessary for safe navigation.

A regulation to this effect was agreed to by the Sub-Committee on Safety of Navigation (NAV) in July 1997, and outlines Governments' responsibilities in carrying out hydrographic surveying, preparing and issuing official nautical charts and promulgating notices to mariners to keep charts up to date.  This regulation is part of the revision of Chapter V, which will enter into force in 1 July 2002.

Electronic charts

Electronic ChartAttention is also focusing on electronic charts, which are already being used on some ships as an addition to paper charts.  Electronic charts carry out the same function as paper charts - they are used for planning and displaying the route for the intended voyage and monitoring the ship's position throughout the voyage.  But electronic chart systems (ECS) have the advantage of automatically displaying the cartographic data necessary related to the ship's position and updated.  There are basically two types of electronic charts, vector and raster.

Electronic charts

A raster chart is basically just a scanned image of a paper chart represented as blocks or pixels rather than points as in vector.  It is a computer-based system, which uses charts issued by, or under the authority of, a national hydrographic office, together with automatic continuous electronic positioning, to provide an integrated navigational tool

In a vector chart, each point on the chart is digitally mapped, allowing the information to be used in a more sophisticated way, such as clicking on a feature (for example, a lighthouse) to get all the details of that feature displayed.  The international standard for vector charts has been finalised by the International Hydrographic Organization (S-57, Edition 3).  Vector charts, used in Electronic Chart Display and Information Systems (ECDIS), have already been accepted as equivalent to paper charts.  Standards for ECDIS were defined by IMO in 1995 in Assembly resolution A.817 (19), while a new section on back-up requirements was adopted in December 1996 in the form of an MSC resolution (MSC.64 (67)) as well as IHO and the International Electrotechnical Committee (IEC).

Many people in the maritime sector accept that the ENCs represent the preferred digital charting system of the future, but it may take years before vector charts necessary to support ECDIS (right) is globally available.  Hence, raster charts are also in use.

Performance standards for electronic charts were adopted in 1995 (resolution A.817 (19)) and later amended in 1996 by resolution MSC.64 (67) to reflect back-up arrangements in case of ECDIS failure.  Additional amendments were later introduced in 1998 under resolution MSC 86 (70) to permit the operation of ECDIS in raster or RDS mode.

Navigational equipment

In addition to charts, equipment used in aid of navigation has to conform to performance criteria and standards set notably by IMO as reflected in SOLAS Chapter V:


Performance standards for navigational equipment – resolutions adopted

A.224 (VII)

Echo-sounding equipment

A.342 (IX)

Automatic pilots

A.382 (X)

Magnetic compasses: carriage and performance standards

A.384 (X)

Radar reflectors

A.424 (XI)


A.477 (XII)

Radar equipment

A.526 (13)

Rate-of-turn indicators

A.665 (16)

Radio direction-finding systems

A.700 (17)

Narrow-band direct-printing telegraph equipment for the reception of navigational and meteorological warnings and urgent information to ships (MSI) by HF

A.813 (19)

Electromagnetic compatibility (EMC) for all electrical and electronic ship's equipment

A.816 (19)

Shipborne DECCA navigator receivers

A.817 (19)

Electronic chart display and information systems (ECDIS)

A.818 (19)

Shipborne LORAN-C and CHAYKA receivers

A.819 (19)

Shipborne global positioning system (GPS) receiver equipment

A.820 (19)

Navigational radar equipment for high-speed craft

A.821 (19)

Gyro-compasses for high-speed craft

A.822 (19)

Automatic steering aids (automatic pilots) for high-speed craft

A.422 (XI)

Automatic Radar Plotting Aids (ARPAs) (equipment installed before 1 January 1997)

A.823 (19)

Automatic Radar Plotting Aids (ARPAs) (equipment installed after 1 January 1997)

A.478 (XII)

Devices to indicate speed and distance (equipment installed before 1 January 1997)

A.824 (19)

Devices to indicate speed and distance (equipment installed after 1 January 1997)

MSC.53 (66)

Shipborne GLONASS receiver equipment

Under SOLAS Chapter V,  
Standard Marine Vocabulary

The importance of effective communication between shipmasters, crew and coastal authorities, especially during a navigational or other emergency,  has long been recognised by IMO.  In 1977, IMO adopted a specially developed English language vocabulary designed for use at sea, called the Standard Marine Navigational Vocabulary (SMNV).

In 1981, IMO adopted a resolution recommending the SMNV be used for communications on board ship as well as those between ships and between ship and shore.  SMNV is now being updated by Standard Marine Communication Phrases or SMCP, which is designed to be more comprehensive that SMNV. 

Following agreement at the Maritime Safety Committee at its 68th session in May-June 1997, the SMCP has been distributed to member governments, maritime training institutes and others involved in maritime communications so that trials can be conducted with a view to the SMCP being reviewed and finally put forward for formal adoption at IMO's 22nd Assembly in 2001.

The SMCP includes phrases that have been developed to cover the most important safety-related fields of verbal shore-to-ship (and vice-versa), ship-to-ship and on-board communications.  The aim is to get round the problem of language barriers at sea and avoid misunderstandings, which can cause accidents.  

The SMCP builds on a basic knowledge of English and has been drafted in a simplified version of maritime English.  It includes phrases for use in routine situations such as berthing as well as standard phrases and responses for use in emergency situations.

The World-Wide Navigational Warning Service

Navigation aids
Navigational warnings to ships are provided through the World-Wide Navigational Warning Service (WWNWS), which was established by IMO, in collaboration with the IHO, in the 1970s. 

Under this system, formally adopted by IMO in 1979 by resolution A.419 (XII) (revising a version adopted in 1977), the world's oceans are divided into l6 navigational areas (called NAVAREAs) and one designated country in each area is responsible for disseminating navigational information.  The language used is English, although warnings can additionally be broadcast in one or more official United Nations' language.

Ships receive the navigational warning via the NAVTEX automated warning system (which has a maximum range of up to about 500 nautical miles) or via INMARSAT satellite SafetyNET service, in areas not covered by NAVTEX.  Since 1 August 1993, ships have been required under SOLAS (Chapter IV, Radiocommunications, Regulation 1.4) to carry a receiver capable of receiving the NAVTEX broadcasts if sailing in an area where they can be received.

Information broadcast under WWNWS

Casualties to lights, fog signals and buoys affecting main shipping lanes

Dangerous wrecks in or near main shipping lanes

Presence of large and unwieldy tows in congested waters

Important new navigational aids (such as new lighthouses or beacons)

Search and rescue and anti-pollution operations

Newly-discovered reefs, rocks and similar hazards

Unexpected changes in established routes

Establishment of offshore structures in or near shipping lanes

Malfunction of radio-navigation services

Underwater operations, such as cable or pipe-laying in or near shipping lanes

Special operations, for example naval exercises

Drifting mines

Notification of ships reported in distress, seriously overloaded or missing



NAVTEX messages are normally sent only in English using narrow-band direct printing (NBDP) and are received on board the ship on a special printer. 

The NAVTEX system, which operates on 518 kHz, was first tried out in Sweden in 1977, and in  1979 countries bordering the Baltic Sea established the first NAVTEX network, which was then  extended to NAVAREA I, which covers the sea areas off north western Europe.  Now all NAVAREAS broadcast NAVTEX messages. 

It was recognized at the start that NBDP offered an excellent means of sending out the messages that are in written form and can be studied at leisure is important, especially when the recipients are not fluent in English.   Another advantage is that information, which is required can be selected by the operator on the equipment so that which is not needed will not be printed.   However, important information, which should be received by all ships will always be printed.

Although the receiving ship can be selective to some extent, and the receiver is unattended, a ship cannot reject navigational and meteorological warnings and search and rescue information.  However, NAVTEX is not regarded primarily as a means of transmitting distress information - this is done on specified distress and safety frequencies.

International NAVTEX messages are broadcast at fixed times on 518 kHz in English.  But in many areas there is interest in transmitting similar information in a second language (for the benefit of local shipping, fishermen and so on).  Important messages may be transmitted in national languages on 518 kHz and in some areas messages are also be sent out on the 4 MHz frequencies.

Although IMO's chief interest is the safety of ocean-going merchant shipping, NAVTEX can also be of great value to smaller craft, such as private yachts, as the cost of NAVTEX equipment is not prohibitive. 


In the areas of the oceans where ships cannot receive terrestrial NAVTEX messages, ships can receive navigational warnings by satellite via the SafetyNET enhanced group calling service.

SafetyNET was developed by INMARSAT (International Mobile Satellite Organization), which was established by IMO in the 1970s.

Now, virtually any ship in the world can receive navigational warnings via NAVTEX or SafetyNET, if they have the right equipment.

Today - and the future
In December 2000, the MSC adopted amendments to Chapter V of SOLAS, which entered into force on 1 July 2002.  The new chapter has been enlarged to 35 regulations from the existing 23 and a new appendix gives rules for the management, operation and financing of the North Atlantic Ice Patrol.  Among the many changes made, the new chapter makes it mandatory for passenger ships and other ships of 3,000 tons gross tonnage and above to carry voyage date recorders.  Like the black boxes carried on aircraft, VDRs enable accident investigators to review procedures on board a ship in the moments before an incident, thereby helping to identify the causes of any accident.  IMO will also study the need for VDRs on existing cargo ships.

The amendments also make it mandatory for new ships built after 1 July 2002 to be fitted with automatic identification systems (AIS), while most existing ships will also have to be fitted with AIS according to an approved phase-in programme.

The amendments give a big boost to the introduction of Electronic Chart Display and Information Systems (ECDIS).  Regulation 19 of SOLAS permits these to be accepted as meeting chart carriage requirements, although are still required to carry back-up arrangements.
It seems likely that in the future, the regulations will be further revised to take into account the other changes that are now transforming navigation at sea.  Before long, even the smallest ships – including pleasure craft – will be able to carry GPS and other position-fixing systems and to communicate with the shore and other ships by means of light-weight radio equipment.  Even greater changes can be expected in the future, which will improve efficiency, lower costs – and save lives.

[1]Governments intending to establish a new routeing system, or amend an existing one, must submit proposed routeing measures to IMO's Sub-Committee on Safety of Navigation (NAV), which will then evaluate the proposal and make a recommendation regarding its adoption. The recommendation is then passed to the MSC for adoption.

[2]The Maritime Safety Committee normally meets twice a year, the Assembly only once every two years.

[3] The National Maritime Museum, London