cardinal mark

cardinal mark, a buoy, normally a pillar, or spar, buoy. It is used in the IALA maritime buoyage system to show that the deepest water in the area in which it is moored is on the side of the quadrant to which the mark belongs. It is also used to show the safe side on which to pass a danger, or to draw attention to a feature in a channel such as a bend, a junction, a bifurcation, or the end of a shoal. Its name indicates which side it should be passed on, e.g., a north cardinal mark, covering between NW and NE, should be passed to the northward. It is coloured with black and yellow bands and the arrangement of these, and of the mark's black topmark consisting of two cones, identifies to which the four quadrants of the compass the mark belongs. The one covering the northern quadrant (NW and NE) has a top band of black and a bottom one of yellow with both topmark cones pointing upwards; the one covering the east quadrant (NE to SE) has its bands arranged black-yellow-black with both topmark cones pointing away from each other; the one covering the south quadrant (SE to SW) has a top band of yellow and a bottom one of black with both topmark cones pointing downwards; and the one covering the west quadrant (SW to NW) has its bands arranged yellow-black-yellow with its topmark cones pointing towards each other. Cardinal marks have a special characteristic of quick flashing, or very quick flashing, white lights.