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Seafaring A-Z Alphabet – “N” is for…


Seafaring “N” is for…

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Navigation – Navigation is about knowing where you are and the route to be taken to get somewhere else you wish to go. It involves the process of monitoring and controlling the movement of a craft or vehicle in that journey. While the disciplines include land, air and space – marine navigation is obviously key for shipping.

All navigational techniques involve locating the navigator’s position, and so navigation, in a broader sense, refers to any skill or study that involves the determination of position and direction.

The term stems from 1530s, from Latin “navigationem” (nom. navigatio), from “navigates”, pp. of “navigare” “to sail, sail over, go by sea, steer a ship,” from navis “ship” and the root of agere “to drive”.

In the European medieval period, navigation was considered part of the set of seven mechanical arts, none of which were used for long voyages across open ocean. Polynesian navigation is probably the earliest form of open ocean navigation, it was based on memory and observation recorded on scientific instruments like the Marshall Islands Stick Charts of Ocean Swells.Early Pacific Polynesians used the motion of stars, weather, the position of certain wildlife species, or the size of waves to find the path from one island to another.

Maritime navigation using scientific instruments such as the mariner’s astrolabe first occurred in the Mediterranean during the Middle Ages, and prompted open-seas navigation during the Age of Discovery in the 15th century.

In 1492 Christopher Columbus’s expedition to sail west to reach the Indies by crossing the Atlantic, resulted in the Discovery of America. While in 1498, Vasco da Gama reached India by sailing around Africa, opening up direct trade with Asia. The first circumnavigation of the earth was completed in 1522 with the Magellan-Elcano expedition, a Spanish voyage of discovery led by Portuguese explorer Ferdinand Magellan and completed by Spanish navigator Juan Sebastián Elcano.

These navigators, with their new instruments, calculations, techniques and bravery to use them, shaped the modern world – they found new continents and nations, and fuelled global trade.Most modern navigation relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on crossing lines of position or LOP. A line of position can refer to two different things: a line on a chart and a line between the observer and an object in real life.

If the navigator draws two lines of position, and they intersect he must be at that position. A fix is the intersection of two or more LOPs. If only one line of position is available, this may be evaluated against the Dead reckoning position to establish an estimated position.

A bearing is a measure of the direction to an object. If the navigator measures the direction in real life, the angle can then be drawn on a nautical chart and the navigator will be on that line on the chart.

In addition to bearings, navigators also often measure distances to objects. On the chart, a distance produces a circle or arc of position. Circles, arcs, and hyperbolae of positions are often referred to as lines of position.

Lines (or circles) of position can be derived from a variety of sources:

• Celestial observation,
• Terrestrial range (natural or man-made) when two charted points are observed to be in line with each other,[18]
• Compass bearing to a charted object,
• Radar range to a charted object,
• A depth sounding from echo sounder or hand lead line.

Navigation has evolved so far in a relatively short space of time, each evolution and new method has enhanced the ability to complete a voyage safely and accurately. Though each has its own risks, and the real art and science of the navigator is of understanding techniques to plot a position when the preferred option is no longer available.

Naval Architecture

Naval architecture

Naval Architecture – Naval architecture deals with the engineering design process, shipbuilding, maintenance, and operation of marine vessels and structures. It involves basic and applied research, design, development, design evaluation and calculations during all stages of the life of a marine vehicle.

From the preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved, naval architecture embraces all the creation elements of a ship.

Naval architecture also involves formulation of safety regulations and damage control rules and the approval and certification of ship designs to meet statutory and non-statutory requirements.

The key elements of naval architecture relate to the material construction and structural build of the vessel – so that the arrangements are able to deal with the demands of the environment, safety and the need to perform whatever task will be expected of the ship.

Construction of the vessel depends on the material used, and the naval architect will produce the design which are used to construct the plates and profiles, so detailed guidance on the marking, cutting and bending as per the design drawings or models, followed by erection and launching.

The structure of a vessel involve selection of material of construction, structural analysis of strength of the vessel, vibration of the structural components and structural responses of the vessel during motions in seaway. While the arrangements involves concept design, layout and access, fire protection, allocation of spaces, ergonomics and capacity.

Two of the biggest challenges which any vessel has to overcome are hydrostatics and hydrodynamics. Hydrostatics concerns the conditions to which the vessel is subjected to while at rest in water and its ability to remain afloat. This involves computing buoyancy, the displacement of the vessel and properties, such as trim and stability.

Hydrodynamics concerns the flow of water around the ship’s hull, bow, and stern, and over bodies such as propeller blades or rudder, or through thruster tunnels. Naval architecture calculates the resistance in water and produces powering calculations which affect the propulsion used.

Naval Architecture is an engineering discipline which looks after the whole ship – and so a Naval Architect is involved in not just the design of vessels, but also all aspects of manufacture right through to launch, test and commission.

Naval architects, marine engineers and nautical surveyors often work together carrying out tests, surveys and procedures. The role also covers aspects of manufacture through to launch, test and commissioning. It is a highly skilled and technical discipline, and ever more sophisticated as the use of computer simulation modelling and physical model tank testing is used.

Nautical Mile

Nautical mile

Nautical Mile – A nautical mile is a unit of measurement defined as exactly 1852 meters (about 6,076.1 feet or 1.1508 statute miles). Historically, it was defined as one sixtieth of the distance between two parallels of latitude separated by one degree.

Today it is an SI derived unit, being rounded to an even number of meters. Until 1929, there was not an internationally agreed upon distance or definition for the nautical mile. In that year, the First International Extraordinary Hydrographic Conference was held in Monaco and determined that the international nautical mile would be exactly 6,076 feet (1,852 meters).Currently this is the only definition and it is the one that is accepted by the International Hydrographic Organization and the International Bureau of Weights and Measures.

The word mile is from the Latin word for a thousand paces: “mīlia”. Navigation at sea was done by eye until around 1500 when navigational instruments were developed and cartographers began using a coordinate system with parallels of latitude and meridians of longitude. In 1617 the Dutch scientist Snell assessed the circumference at 24,630 Roman miles (24,024 statute miles).Nautical miles are typically abbreviated with the symbols nm, “NM” or “nmi”. The measurement is used in navigation and aviation, but nautical miles are also used polar exploration and international laws and treaties regarding territorial water limits.

In addition, nautical miles are also still significant markers of speed as the term “knot” is used to mean one nautical mile per hour. Today knot measurements have become more sophisticated than the old rope dragged along the ship, and are determined by advanced methods such as mechanical tow, Doppler radar, and/or GPS.

Because nautical miles have constant measurement following lines of longitude, they are extremely useful in navigation. Usually, nautical charts use one of three map projections:

• Gnomic,
• Polyconic, and
• Mercator.

The Mercator projection is the most common of these three because on it, lines of latitude and longitude cross at right angles forming a rectangular grid. On this grid, the straight lines of latitude and longitude work as straight line courses and can easily be plotted through the water as navigable routes.

The addition of the nautical mile and its representation of one minute of latitude make navigation relatively easy in open water, thus making it an extremely important component of exploration, shipping and geography.

Neap Tide

Neap tide

Neap Tide – Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The tidal range is the vertical difference between the high tide and the succeeding low tide. It is not constant, but changes depending on where the sun and the moon are.The position of the sun and moon give rise to spring and neap tides.

The most extreme tidal range occurs around the time of the full or new moons, when the gravitational forces of both the Sun and Moon are in phase, reinforcing each other in the same direction (new moon), or are exactly the opposite phase (full). This type of tide is known as a spring tide.

Neap tides occur when the Sun and Moon are at right angles to one another as seen from Earth. In this case, the gravitational forces counteract each other, creating weaker tidal forces.Tidal data for coastal areas is published by the national hydrographic service of the country concerned, and is based on astronomical phenomena and is predictable.

During the neap tides the difference between high and low tides is smaller, and they occur during the first and last quarters of the moon’s phases. The largest annual tidal range can be expected around the time of the equinox, if coincidental with a spring tide.

Tides are usually calculated and predictable – but weather can have an effect too – not just the push or pull of the sun and moon. Storm force winds blowing from a steady direction for a prolonged time interval combined with low barometric pressure can increase the tidal range, particularly in bays, rivers or estuaries – where walls of water can be pushed along and rise up. Such weather-related effects on the tide, which can cause ranges in excess of predicted values and can cause localised flooding, are not calculable in advance.



Neptune – According to Roman religion, Neptune was the name that ancient Romans gave to the Greek god of the sea and earthquakes, Poseidon. He was the brother of Jupiter (Zeus) and of Pluto (Hades).

After the defeat of their father Saturn (Cronos), the three brothers divided the world in three parts to be ruled by one of the three brothers. Jupiter took the sky, Neptune the sea and Pluto the underworld.

Neptune had the reputation for having a violent temper. Tempests and earthquakes were a reflection of his furious rage. In earlier times it was the god Portunes or Fortunus who was thanked for naval victories, but Neptune supplanted him in this role by at least the first century BC, when Sextus Pompeius called himself “son of Neptune”.

Initially Neptune was associated with fresh water, as opposed to Oceanus, god of the world-ocean – but that changed, and Neptune was accepted as being considered god of the sea. He was represented in this role, with black or dark hair wearing garments of an azure or sea-green colour and seated in a large shell chariot drawn by whales, horses or even sea-horses.He is always pictured with his trident in his hand and is usually attended by sea gods and sea goddesses and a retinue of Tritons and sea-nymphs. On ancient some coins and medals he is depicted mounted on the beak of a ship as a clear indication that he presided over the seas. Neptune was also the patron of horse racing, and was believed by the ancients to have been the creator of the horse.

Neptune has always featured heavily in the ceremony of “Crossing the Line” – an initiation rite in many navies and under certain flags, which commemorates a seafarer’s first crossing of the Equator.

The tradition may have originated with ceremonies when passing headlands, and become a “folly” sanctioned as a boost to morale, or have been created as a test for seasoned sailors to ensure their new shipmates were capable of handling long rough times at sea. Equator-crossing ceremonies, typically featuring King Neptune, are also sometimes carried out for passengers’ entertainment on cruise ships. They are also performed in the merchant navy and aboard sail training ships – they were historically brutal affairs with those being initiated into “Neptune’s Court” being shaved and covered in all manner of nasty substances, but this has now calmed down.



Noon – Noon (also midday or noon time) is usually defined as 12 o’clock in the daytime. Solar noon is when the sun crosses the meridian and is at its highest elevation in the sky, at 12 o’clock apparent solar time. The local or clock time of solar noon depends on the longitude and date.

This was one of the most significant times onboard a ship in the pre-GPS days. This was when a “noon sight” was taken of the sun, and the vessel’s position taken. This allowed a noon report to be produced, initially just logged – but with the advent of radio and then satellite communications, then the noon report was sent to the head office each day.This report provided owners with a snap shot of all the facts they needed about the vessel’s position and the data to assess the performance of the ship based on its speed and environmental forces including weather conditions.

The noon report is also used to analyse vessel performance – and is especially important for consumption of fuel and lube, as well as distances covered and the time taken.The noon reports are traditionally sent by the captain every day, with the content and format agreed by the company. Obviously the basics such as name, date and voyage numbers. There is much more to be included too.

The primary purposes remains, and the position of the ship is reported. From this, there is data such as average speed since last noon report in knots, as well as engine data such as fuel and water consumption, and levels of fuel, lube, water remaining onboard. There is also data on the average engine revs and the total revolutions of the propeller from noon to noon.The conditions experienced by the vessel are also important – so the noon report still encompasses wind Direction and wind force, as well as sea and swell conditions. In addition the distance to next port of call/ destination and the Estimated Time of Arrival (ETA).

The noon report is one of the important documents on board ships that is recorded ad used for future references, and it is also a very useful means of benchmarking and checking performance of other vessels too.

Now with constant monitoring and performance data being beamed back to the office ashore, the importance and significance of the noon report is lessened – but there is still a flurry of activity each day to ensure that all the relevant updates are compiled and the vessel is reporting as it should.

Notices to Mariners – Notice to mariners advises mariners of important matters affecting navigational safety, including new hydrographic information, changes in channels and aids to navigation, and other important data.

In addition, the UK Flag for instance issues three different types of “Marine Shipping Notice” which promulgate and publicise to the shipping and fishing industries important safety, pollution prevention and other relevant information. The notices are:

Merchant Shipping Notice (MSN) – Used to convey mandatory information that must be complied with under UK legislation. These MSNs relate to Statutory Instruments and contain the technical detail of such regulations.

Marine Guidance Notices (MGN – Which give significant advice and guidance relating to the improvement of the safety of shipping and of life at sea, and to prevent or minimise pollution from shipping.

Marine Information Notices (MIN) – which are intended for a more limited audience e.g. training establishments or equipment manufacturers, or contain information which will only be of use for a short period of time, such as timetables for MCA examinations. MINs are numbered in sequence and have a cancellation date (which will typically be no more than twelve months after publication).

Within each series of Marine Notices suffixes are used to indicate whether documents relate to merchant ships or fishing vessels, or to both. The suffixes following the number are:

• (M) for merchant ships
• (F) for fishing vessels
• (M+F) for both merchant ships and fishing vessels

Merchant Shipping Notices can be downloaded from the MCA Website under “Guidance and Regulations”.

It is not solely the UK – over 60 countries which produce nautical charts also produce a notice to mariners. About one third of these are weekly, another third are bi-monthly or monthly, and the rest irregularly issued according to need. For example, the United Kingdom Hydrographic Office issues weekly updates.

As examples, the U.S. Notice to Mariners is made available weekly by the National Geospatial-Intelligence Agency (NGA), prepared jointly with the National Ocean Service (NOS) and the U.S. Coast Guard. The information in the Notice to Mariners is formatted to simplify the correction of paper charts, List of Lights, Light Lists, United States Coast Pilots, and other publications produced by NGA, NOS, and the U.S. Coast Guard.

While the Canadian Coast Guard (CCG) Notice to Mariners publication informs mariners of important navigational safety matters affecting Canadian Waters. This electronic publication is published on a monthly basis and can be downloaded from the Notices to Mariners (NOTMAR) Web site. The information in the Notice to Mariners is formatted to simplify the correction of paper charts and navigational publications.

A close companion to the Notice to Mariners is the Summary of Corrections. The Summary is published in five volumes. Each volume covers a major portion of the earth including several chart regions and many sub-regions. Volume 5 also includes special charts and publications corrected by the Notice to Mariners. Since the Summaries contain cumulative corrections, any chart, regardless of its print date, can be corrected with the proper volume of the Summary and all subsequent Notice to Mariners.