Marine navigation lights are simply coloured electric lights fixed on ships and used to indicate the size of the ship, the direction in which the ship is travelling, the angle where they should be visible. They must be exhibited by law between sunset and sunrise and in poor visibility.
The location (on the ship), the range (distance at sea to which these lights can be seen) and the arc of visibility of these lights (the angle through which they can be seen) is fixed by international convention. In fact, all marine navigational lights must comply with rigid international standards and be fixed by approved personnel. It is important to understand that international conventions cover all vessel’s everywhere in the world, from the smallest boat (which can carry a torch) to the largest oceangoing behemoth. A few countries like the US have special rules for inland navigation within their rivers etc., but they don’t usually deviate in a major way from international conventions.
A ‘normal’ ship shows ‘running lights’ at sea, as explained below
- A ship at anchor, and all specialised ships like minesweepers, dredgers, high speed ferries- and a plethora of such- must show special lights. So must fishing vessels, towing vessels and big ships restricted in their ability to manoeuvre by virtue of their size. All lights, normal or special, are constructed and fixed on ships according to international law.
- The 'range' of lights- that is, the distance from which they can be seen, varies. As an example, the masthead light of a big oceangoing vessel may have a range of 6 miles; a boat under 20 metres in length only 3 miles. In practice, conditions of visibility and height of the observer affect the range at which these can be seen.
