Safe Water Marks. Safe Water marks serve to indicate that there is navigable water all round the mark. These include centre line marks and mid-channel marks. Such a mark may also be used to indicate channel entrance, port or estuary approach, or landfall. The light rhythm may also be used to indicate best point of passage under bridges.

LIGHT FLASH CHARACTERS.  All lighted aids to navigation, with the exception of those aids equipped with fixed (continuous) lighting, follow an established light flash character pattern. Such characters describe the periodic rhythm of a navigation light, thus enabling it to be identified on charts or while in visual contact.

Sector Lights

Definition of Sector Lights

A sector light is a fixed aid to navigation that displays a light of different colours and/or rhythms over designated arcs. The colour of the light provides directional information to the mariner.

Isolated Danger marks. Isolated Danger marks are erected on, or moored on or above, isolated dangers of limited extent which have navigable water all round them. The extent of the surrounding navigable water is immaterial: such a mark can, for example, indicate either a shoal which is well offshore, or an islet separated by a narrow channel from the coast.

Cardinal marks. Cardinal marks are used in conjunction with the compass to indicate where the mariner may find the best navigable water. They are placed in one of the four quadrants (North, South, East and West) bounded by inter-cardinal bearings, from the point marked.

Marking new dangers. Definition of New Dangers 

The term “New Danger” is used to describe newly discovered hazards not yet shown in nautical documents. ‘New Dangers’ include naturally occurring obstructions such as sandbanks or rocks or man-made dangers such as wrecks.

Lighthouses

Definition of a Lighthouse

A lighthouse is a tower, or substantial building or structure, erected at a designated geographical location to carry a signal light and provides a significant daymark. It provides a long or medium range light for identification by night.

Special marks. 

Definition of Special Marks

Marks used to indicate a special area or feature whose nature may be apparent from reference to a chart or other nautical publication. They are not generally intended to mark channels or obstructions where other marks are more suitable.

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