The main purpose of a Cardinal Mark is to indicate the safe side on which to pass a danger.
The deepest water is on the named side.
The buoys always carry a topmark consisting of two cones which, from a distance, appear like arrows. To help remember the meaning of the arrows, those on the North and South Cardinals point north and south as if on a compass rose. West has inward arrows, which look like a Wineglass, or a “W” on its side. East is the only one remaining (arrows outward).
Take the North Cardinal Mark as an example. The diagram shows that it is placed north of the danger. When you see two arrows pointing upwards, they are pointing towards the clear water. So when you see a North Cardinal marks, it can be helpful to think of it as a “CLEAR WATER NORTH” mark.
Likewise, think of the others as “CLEAR WATER WEST”, “CLEAR WATER EAST” and “CLEAR WATER SOUTH”. Another look at the diagram will indicate that if your vessel is proceeding northwards and you see a North Cardinal Mark in front of you, you would be heading for trouble, because the clear water is north of it!
The buoys are coloured black and yellow. The direction of the arrows relates to the position of the black bands. If the arrows point both up and down (as with the East Cardinal) the black is at both top and bottom of the buoy.
If the Standard Code is used, the retro-reflectors would be white band(s) with letters, numerals or symbols. If the Comprehensive Code is used, the black and yellow bands on the buoy are represented by blue and yellow retro-reflectors.
For the East Cardinal the two blue retro-reflectors would be on the top (black) part of the buoy, and for the West Cardinal the two yellow retro-reflectors would be on the top (yellow) part of the buoy. For North and South there would be one retro-reflector on each colour.
To memorise the light combinations of Cardinal marks, think of a clock face.
At 3 o’clock there are 3 flashes, at 6 o’clock there are 6 flashes, and at 9 o’clock there 9 flashes, with continuous flashing at 12 o’clock.
At 6 o’clock there is an additional long flash to aid a quick and positive identification. Buoys get tossed around in rough weather and sometimes it can be difficult to count the flashes.
Lights on Cardinal Marks either flash “Quick” (usually 50-60 per minute) or “Very Quick” (usually 100-120).
The light sequence is repeated every 5 or 10 seconds for the East Cardinal, and 10 or 15 seconds for South and West, the shorter periods being for the very quick flash. mlr08_s10_uf02_co.eps
A Cardinal Mark may also be used to indicate a feature in a channel, such as a bend, junction, or the end of a shoal.