Cardinal marks
A cardinal mark tells you which side of it the safer water lies — north, east, south or west. They are the same in Region A and Region B. Here are the quadrants, topmarks, colours and every light character, summarised in our own words from IALA Recommendation R1001.
Where safer water lies in relation to a point of interest, such as a danger. The safer navigable water lies on the side the mark is named for: to the north of a north cardinal, to the east of an east cardinal, and so on. The type of mark tells you which side of it to pass.
That is not the only safe water: R1001 notes there may also be navigable water on other sides of the mark (east and west of a north cardinal, for example), and says to consult the chart.
Four quadrants, measured in true bearings from the point of interest: north between NW and NE, east between NE and SE, south between SE and SW, and west between SW and NW. As we read it, a north cardinal mark is placed in the north quadrant of the point it marks, and so on round the compass.
R1001 gives three examples: to show where the deepest water in an area is; to show the safe side on which to pass a danger; and to draw attention to a feature in a channel, such as a bend, a junction, a bifurcation or the end of a shoal.
It also warns authorities against laying too many in one waterway, because their white lights look alike and can confuse.
Yes. R1001 states that the cardinal marks and their use are the same in both regions. Only lateral marks change between regions.
Two black cones pointing up, one above the other, on a pillar or spar that is black above yellow. If it is lit, the light is white, very quick (VQ) or quick (Q) flashing, with no grouping.
Two black cones base to base, on a black pillar or spar with one broad yellow band across it. If lit: white, VQ(3) every 5 s or Q(3) every 10 s.
Two black cones pointing down, on a pillar or spar that is yellow above black. If lit: white, VQ(6) + long flash every 10 s or Q(6) + long flash every 15 s.
Two black cones point to point, on a yellow pillar or spar with one broad black band across it, a third of its height. If lit: white, VQ(9) every 10 s or Q(9) every 15 s.
They have no distinctive shape — normally a pillar or spar. They are always painted in yellow and black horizontal bands, their double-cone topmark is always black, and their light, when fitted, is always white. R1001 calls the double-cone topmark 'a very important feature' by day, to be used wherever practicable, as large as possible and with a clear gap between the cones.
Ours, not R1001's: the cones point to where the black is. North cones point up, and the black is on top. South cones point down, and the black is at the bottom. East cones point outwards, base to base, and the black is top and bottom. West cones point inwards, point to point, and the black is in the middle.
And for the shape of the topmark: north points up and south points down, like a chart; east's base-to-base cones make a diamond, west's point-to-point cones an hourglass.
Very quick (VQ) flashing is a light flashing at 120 or 100 flashes a minute. Quick (Q) flashing is 60 or 50 flashes a minute. Every cardinal light is one or the other; each type of mark uses a different sequence. Where similar cardinal marks are close together, R1001 says they should use different characters.
R1001 itself suggests a clock face: three flashes for east (3 o'clock), six for south (6 o'clock), nine for west (9 o'clock). North has no group: R1001's table gives it as plain VQ or Q, with no number and no period.
So that three or nine flashes can't be mistaken for six. The long flash is defined as a light appearance of not less than 2 seconds, and it follows the six very quick or quick flashes: VQ(6) + long flash every 10 s, or Q(6) + long flash every 15 s.
R1001 says not: the two other marks with white lights, the isolated danger mark and the safe water mark, each have a rhythm that can't be confused with the very quick or quick flashing of a cardinal. In practice, the thing to watch is two cardinals near each other — count the flashes and time the period.
Examples of the kind of question to be ready for (our wording, not the MCA's):
“Describe a west cardinal mark by day and at night.”
“You see a white light, quick flashing, six flashes followed by a long flash. What is it, and where is the safe water?”
“How are the cardinal quadrants defined?”
“Why does the south cardinal have a long flash?”
The common slips: mixing up the east and west topmarks, passing on the wrong side (a south cardinal is passed to its south), and forgetting the period — Q(9) is every 15 s, VQ(9) every 10 s.
The notices change. Always check the current version on GOV.UK before you apply or book.
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