Cardinal Mark

An aid to navigation indicating that the named side of the mark is the side on which to pass or find the safest water.

North, east, south and west cardinal marks are named for the quadrant in which they lie relative to a danger or feature. Their black-and-yellow bands, paired cone topmarks and, when fitted, characteristic white-light rhythms identify the relevant quadrant.

A cardinal mark may indicate the safe side of a danger, the deepest water in the area or a feature such as a bend, junction or end of a shoal. It does not merely warn vessels away from every side, and the chart and surrounding marks must be used to understand the feature being marked.