A cardinal mark is placed in one quadrant of a danger and named for the compass direction in which navigable water lies: you pass a north cardinal to its north, a south cardinal to its south. That single sentence is the whole system. Every visual feature is a way of telling you which of the four it is, and the features are consistent with each other, which is what makes them learnable. Cardinal marks are identical in IALA Region A and Region B.

Start with the cones

Each cardinal mark carries two black cones, one above the other. The cones are the primary identifier and the part to learn first:

  • North: both cones point up. Up is north on the chart.
  • South: both cones point down.
  • East: cones base to base, making an egg shape — “E for egg”.
  • West: cones point to point, making a wineglass — “W for wineglass”.

The colours follow the cones

Cardinal marks are painted in yellow and black horizontal bands. Rather than memorising the band order, notice that black is always where the cones point:

  • North: cones point up, so black is on top, yellow below.
  • South: cones point down, so black is at the bottom, yellow above.
  • East: cones point up and down, away from each other, so black is at the top and bottom with a single broad yellow band in the middle.
  • West: cones point to the middle, so black is in the middle with yellow above and below.
The four cardinal marks side by side. North: two black cones pointing up, black band above yellow, continuous quick or very quick white light. East: cones base to base, black with a yellow band in the middle, three flashes. South: two cones pointing down, yellow above black, six flashes plus a long flash. West: cones point to point, yellow with a black band in the middle, nine flashes. The black band or bands sit where the cones point.North cardinalboth cones point UPblack over yellowwhite light:VQ or Q, continuousEast cardinalcones base to baseblack, yellow band, blackwhite light:VQ(3) 5s / Q(3) 10sSouth cardinalboth cones point DOWNyellow over blackwhite light:VQ(6)+LFl 10s / Q(6)+LFl 15sWest cardinalcones point to pointyellow, black band, yellowwhite light:VQ(9) 10s / Q(9) 15sRule of thumb: the black band(s) are where the cones point. Lights are always white.
What to notice: Cover the labels and test yourself: from the cones alone, name the mark and predict the bands; from the bands alone, predict the cones. The black band sits where the cones point on every one.

Four cardinal marks with their topmarks, colour bands and light rhythms labelled.

The lights follow a clock face

All cardinal marks show white lights, either quick flashing (Q, 50 or 60 flashes a minute) or very quick flashing (VQ, 100 or 120 a minute). Picture a clock face with north at 12:

Cardinal mark light characteristics (IALA R1001 Table 6)
MarkClock positionRhythm
North12Continuous: VQ or Q
East3Three flashes: VQ(3) every 5 s or Q(3) every 10 s
South6Six flashes then one long flash: VQ(6)+LFl every 10 s or Q(6)+LFl every 15 s
West9Nine flashes: VQ(9) every 10 s or Q(9) every 15 s

The long flash — at least two seconds — on the south cardinal exists, in IALA's words, so that three or nine flashes cannot be mistaken for six. If you see a group of flashes followed by a distinctly longer one, it is south, whatever you counted.

Using them in practice

Plan view of a rocky danger in the middle with four cardinal marks placed around it: a north cardinal above it, an east cardinal to its right, a south cardinal below it and a west cardinal to its left. Arrows show that safe water lies to the north of the north mark, east of the east mark, south of the south mark and west of the west mark. The marks show which side to pass, not the size of the danger.NdangerNESWsafe water north of the N marksafe watereast of Esafe water south of the S marksafe waterwest of W
What to notice: Each mark sits in its named quadrant of the danger and navigable water lies beyond it in that direction. Notice what the diagram does not tell you: the size or shape of the danger, which you must take from the chart.

Plan view of a danger with four cardinal marks around it and arrows showing safe water on the named side of each.

When a cardinal comes into view, identify it, then look at the chart to see what it is guarding. A cardinal mark tells you which side is safe; it does not tell you how far the danger extends, and shoals and wrecks often reach a long way from the buoy on the other sides. “Pass to the north” does not mean “shave it” — it means the navigable water is that way, so give the mark the clearance the chart suggests. Where a danger is marked by several cardinals, they combine: passing north of the north cardinal and east of the east cardinal keeps you clear of the whole feature.

Try it: where is the safe water?

A cardinal mark
Safe water lies to the…Safe water lies to the…
Identify the mark from its cones and bands, then choose the side to pass.
What to notice: Work through all four marks. Read the cones first, confirm with the bands, then answer — and note that the reveal always gives the light rhythm too, because at night that is all you get.

Interactive quiz: a cardinal mark is shown and you choose which side the safe water lies; the answer explains the cones, bands and light rhythm.

Check yourselfAt night you see a white light flashing in groups of nine, every fifteen seconds. Which mark is it, what does its topmark look like, and which side do you pass?Show answer

Q(9) 15s is a west cardinal — 9 o'clock on the clock face. Its cones point to point (the wineglass), and by day it is yellow with a single broad black band in the middle, where the cones point. Pass to the west of it: navigable water lies west of the mark, the danger to its east.

Key takeaways

  • A cardinal mark is named for the side on which navigable water lies. Pass on that side.
  • Two black cones: up = north, down = south, base to base = east, point to point = west.
  • Black bands are where the cones point.
  • White lights only: continuous for north; 3, 6 + long, and 9 flashes for east, south and west, in Q or VQ.
  • The mark shows the safe side, not the extent of the danger — read the chart for that.