Cardinal marks

A cardinal mark is a sea mark (a buoy or other floating or fixed structure) used in maritime pilotage to indicate the position of a hazards and the direction of safe water. Cardinal marks indicate the direction of safety as a cardinal (compass) direction (north, east, south or west) relative to the mark. The Mariner is safe if he passes N of a North mark, E of an East mark, S of a South mark and W of a West mark.

Cardinal marks may be used to:

• indicate that the deepest water in an area is on the named side of the mark;

• indicate the safe side on which to pass a danger;

• draw attention to a feature in a channel such as a bend, junction, branch, or end of a shoal;

• draw attention to a new danger such as a grounded ship.

Topmark. Cardinal buoys are fitted with two black cones.

Colours. Black and yellow bands are used to colour Cardinal marks. The position of the black band, or bands, is related to the points of the black topmarks.

Shape. Cardinal buoys are pillar- or spar-shaped.

Light. White lights are exhibited from Cardinal marks which are lighted. Their characteristics are based on a group of quick flashes which distinguish them as Cardinal marks and indicate their quadrant.

Point of interest	Topmarks	Colours	Lights
North	Points up	Black band above yellow band	Uninterrupted
South	Points down	Black band below yellow band	6 flashes in a group followed by a long flash
West	Points inward	Black band with yellow bands above and below	9 flashes in a group
East	Points outward	Black bands above and below yellow band	3 flashes in a group

Isolated Danger marks

A n Isolated Danger mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate a hazard to shipping such as a partially submerged rock in the immediate vicinity of the buoy. Ships should keep clear of it.

Topmark. The isolated danger buoy carries two black spheres (balls), disposed vertically.

Colours. Black with one or more red bands are the colours used for Isolated Danger marks.

Shape. Isolated danger marks are pillar- or spar-shaped.

Light. A white flashing light showing a group of two flashes is used to denote an Isolated Danger mark.

Safe Water marks

A Safe Water mark is a sea mark used in maritime pilotage to indicate the end of a channel. It is used to indicate that there is navigable water (safe water of sufficient depth) all round a mark. Such a mark may be used as a centerline, mid-channel or landfall buoy, or to indicate the best point of passage under a fixed bridges. A ship can pass any side of it.

Topmark. The safe water buoy is fitted with a single red sphere.

Colours. Red and white stripes are used for Safe Water marks.

Shape. Spherical, pillar or spar buoys are used as Safe Water marks.

Light. A white light, occulting (more light than dark), or isophase (equal light and dark), or showing a single long flash every 10 seconds.