Cardinal mark

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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 hazard 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. This makes them meaningful regardless of the direction or position of the approaching vessel, in contrast to the (perhaps better-known) lateral mark system.

The characteristics and meanings of cardinal marks are as defined by the International Association of Lighthouse Authorities.

A cardinal mark indicates one of the four compass directions by:

• its distinctive pattern of black and yellow stripes,
• the direction of its two conical top-marks, and
• optionally, its distinctive sequence of flashing light.

In the diagram, the light sequence is indicated by the white-banded pattern and the notation Q (for quick) or VQ (very quick). Either the quick or the very quick sequence may be used; the choice allows for two similar nearby marks to be uniquely identified by their lights.