‘In 400 metres turn right…’

These days, when driving from A to B, we have our choice of help with navigation, be it a map, usually on our phones, the good old-fashioned method of asking for directions (depending on who’s driving!) and satnav of course.

From a maritime perspective, navigation is a much more structured and collaborative process which involves planning, recording and controlling the movement of vessels from one place to another. Lighthouse Authorities around the world are responsible for ensuring the Aids to Navigation (AtoN) infrastructure and services in their waters.

If you consider that trade by sea is growing and that approximately 95% of all logistics is by sea, the need for rigorous and coordinated AtoN services can be better understood.

 The story of navigation begins

 The earliest sailors would have navigated close to shore using their knowledge of coastal landmarks and natural phenomena (birds, clouds, tides, floating debris) to guide them. The celestial bodies – the sun by day and the stars by night – also helped guide mariners. In fact, they still do.

The first AtoN was developed, it is estimated, in 280BC when a lighthouse was built to mark the entry to the port of Alexandria in Egypt. (It was one of the seven wonders of the ancient world).

By the time of Christopher Columbus, ocean navigation was well underway. We were navigating with magnetic compasses and types of quadrants. The first navigational charts had also appeared. The process of ‘dead reckoning’, where the position of a ship is established and subsequent positions are calculated based on a measured course and speed, was also in use. The speed of a vessel was calculated by throwing a log overboard on a rope with knots tied at known intervals and measuring how many knots played out over a set time interval. This is the origin of the present day term “knots”, which is used to describe the speed of a ship or a current in a body of water.

Later sextants and chronometers were invented and were used to accurately calculate a ship’s latitude and longitude based on observations of the sun and stars. Detailed navigational charts covering the known world also became available to guide mariners. Lighthouses were also becoming more common, and the first floating AtoN to include a burning light was the Lightship Nore established at the mouth of the River Thames in London in 1731.

Man steering boat_ Great Lighthouses of Ireland


National authorities established

In these days of easy transatlantic air travel, it’s easy to forget that at that time, two hundred years ago, all international commerce and communication was by sea. , this explains the vital importance of these AtoNs in facilitating safe sea travel. It was so critical that national AtoN providers were established. The Commissioners of Irish Lights (then the Corporation for Preserving and Improving the Port of Dublin) was set up in 1786 as the National AtoN provider for the island of Ireland.

In the 1900s, radio technology was in its infancy, and the nature of AtoNs had not changed dramatically for many years. A visual system of lighthouse ‘daymarks’ (conspicuously painted, distinctive colours) and lightships by day, and a system of uniquely timed flashing lights by night, coupled with an audible system of fog signals, were provided for mariners at manned lighthouses and lightships. Though there are no longer lighthouse keepers at these stations, these aids are still provided, and are now sometimes known as traditional AtoNs.

Technological advances

Over the course of the last century and to the present day, huge advances have been made in terms of terrestrial and extra terrestrial communication – particularly in the fields of radio and satellite navigation respectively. The more notable terrestrial based systems have been radio beacons, Radio Detection and Ranging (Radar), Decca, and Loran. Of the extra-terrestrial Global Navigational Satellite Systems (GNSS), GPS is the most well-known.

Today, ships have a wealth of systems with which to determine their position, course, and speed relative to hazards and other vessels. A large ship uses a combination of what is known as ‘Heads Up’ – when the ship is guided by a captain viewing the visual surroundings directly, and ‘Heads Down’ navigation, when a ship is guided by reference to an electronic sensor display.

Though new technologies have emerged, navigating by eye using visual AtoNs still plays a huge role in marine safety. Not all those who use our seas are equipped with satellite navigation systems and the latest technology. And, of course, one of the key principles in AtoN provision is that there must be alternatives available in the case of failure of any system. A mix of systems is critical to ensuring safe navigation.

A ship equipped with modern electronic navigation systems, good visual information on her surroundings and an alert and responsible captain, is as good as you’ll get in navigational terms, and ensures the best chance of safety at sea.

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