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Cardinal mark


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:

The topmark configurations for north and south are self-explanatory (both cones pointing up, or both pointing down). Those for east and west "follow the Sun"—the top cone points in the direction in which the rising (for an east mark) or setting (for a west mark) Sun appears to move with respect to the horizon, while the bottom cone points in the direction in which its reflection on the ocean surface appears to move.

Either a quick or a very quick sequence of light flashes may be used; the choice allows for two similar nearby marks to be uniquely identified by their lights.

A cardinal mark may be used to accomplish the following:

Other uses:

Knoll North Cardinal

The 'East Bramble' East Cardinal Mark helps the Stavros S Niarchos navigate safely in the Solent, August 2008

All four types of cardinal mark used in Nanaimo Harbour to warn of an old concrete base.

A light buoying cardinal mark in pressure of ice in front of Helsinki, Finland in winter. Notice that topmark is not used on a buoy that is subjected to ripping by movements of ice.


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