Cardinal marks are yellow and black marks placed north, east, south or west of a hazard, and you pass on the side they are named after: pass north of a north cardinal. The two black cones on top show which one it is.
A cardinal mark tells you where the safe water is in relation to a danger such as a rock, a shoal or a wreck. The mark is named after the compass quadrant it sits in, and the safe water is on that side of it. A north cardinal is placed to the north of the hazard, so you pass to the north of it.
The topmark, two black cones one above the other, shows which mark it is:
- North: both cones point up. The black is above the yellow.
- South: both cones point down. The black is below the yellow.
- East: the cones point away from each other, base to base, a shape often remembered as an egg. Black bands top and bottom, yellow in the middle.
- West: the cones point towards each other, a wasp-waist or wine-glass shape. Yellow top and bottom, a black band in the middle.
The black bands are always where the cones point: up for north, down for south, both ends for east, the middle for west.
At night, cardinal marks show a white light that flashes quickly, very quick (VQ) or quick (Q), in a pattern based on a clock face:
- north: continuous flashing (12 o'clock);
- east: three flashes (3 o'clock);
- south: six flashes followed by one long flash (6 o'clock);
- west: nine flashes (9 o'clock).
Cardinal marks are the same in IALA A and IALA B.
Two cautions. First, the mark shows the safe side, but it does not say how far the danger extends, so look at the chart and give it a generous berth. Second, the quadrant is a compass direction, not left or right, so work out from the compass which side of the mark you are on. If you are heading south towards a north cardinal, you are already on its safe side, and you must not carry on past it to the south.
More in the book: Chapter 14, Buoys, charts and tides