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Lighthouses

A lighthouse is a structure exhibiting a light (a major light). This light serves as an aid to navigation. Lighthouses are always conspicuous.

They are built on land and at sea. In most cases lighthouses are erected on solid foundations.

Lighthouses vary in shape. They can be circular, pyramidal, quadrangular, square, cylindrical, triangular, rectangular, hexagonal and octagonal. They are built of stone, brick, concrete, iron, steel, wood, etc.

Lighthouses are painted white, yellow, red, etc. Sometimes they are painted in horizontal and vertical stripes of different colours (a band is a horizontal line; a stripe is a vertical line). The lights may be fixed, flashing, occulting, alternating, group-flashing.

When leading lights are exhibited, the front light is always lower than the rear light.

Lightship, a distinctively marked vessel anchored or moored at a charted point, to serve as an aid to navigation.

  1. Study the table: Navigational Light Characteristics

Light pattern

Chart abbrev.

Description

F.

Continuous fixed light.

______     ______     ______     ______

Fl.

Flashing. Light shorter than dark.

___           ___           ___           ___

Occ.

Occulting. Dark shorter than light.

___      ___      ___      ___      ___      _

Iso.

Isophase. Equal amounts of light and dark.

___  _  _  ___  _  _  ___  _  _  ___  _  _ 

Gp.Fl.(3)

Group flashing. In this case, groups of three.

_  _            _  _            _  _            _  _

Gp.Occ.(2)

Group occulting. In this case, groups of two.

___  _  __  _____  _  __  _____  _  __ 

Gp.Fl.(2+1)

Composite group flashing.

_  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _ 

Qk.Fl.

Quick flashing 50 or 60 per minute.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

V.Qk.Fl.

Very quick flashing 100 or 120 per minute.

_  _  _  _  _  _  _  _  _  ____  _  _  _  _ 

Int.Qk.Fl.

Interrupted quick flashing.

_ _ _ _ _ _ _ _ _ _ _ ______ _ _ _ _ _ _

Int.V.Qk.Fl.

Interrupted very quick flashing 100 or 120 per minute.

___      ___      ___      ___      ___      _

Alt.

Alternating. Changing colour. In this case white and red.

Notes.

  • The period of a light is the length of time taken (in seconds) to complete one full cycle. E.g. 10s is a period of ten seconds.

  • The height (in metres) of a light above “mean high water springs” (MHWS) is denoted by a small m. E.g. 15m indicates a height of fifteen metres.

  • The range (in nautical miles) at which a light can be seen in good visibility is denoted by a capital M. E.g. 25M indicates a range of twenty five nautical miles.

  • The colour of a light is usually denoted by the first letter. e.g. R is red, G is green.

Example.

A light marked on a chart as 'Gp.Fl.(3)20s 15m 25M' would indicate, a light flashing in groups of three every twenty seconds at a height of fifteen metres above MHWS that could be seen at a distance of twenty five nautical miles in good visibility.