Cardinal marks indicate that the navigable water lies on the named side of the mark. They use black and yellow horizontal bands and two black cone topmarks.
North Cardinal: pass to the north. Topmark: two cones pointing UP. Colours: black above yellow. Light: continuous quick or very quick flashing.
East Cardinal: pass to the east. Topmark: two cones base to base. Colours: black-yellow-black. Light: 3 quick flashes (3 o'clock).
South Cardinal: pass to the south. Topmark: two cones pointing DOWN. Colours: yellow above black. Light: 6 quick flashes + 1 long flash (6 o'clock).
West Cardinal: pass to the west. Topmark: two cones point to point. Colours: yellow-black-yellow. Light: 9 quick flashes (9 o'clock).
An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
Buoyage Reading Order
Read the mark in a fixed order: topmark, colour pattern, light rhythm, charted meaning, then the safe side or action required.
Confirm the conventional direction of buoyage from the chart or pilotage plan before deciding port-hand or starboard-hand treatment.
Treat every mark as one aid among several.
Cross-check with charted depth, position, radar, visual bearings and the planned track.
Exam Focus
For cardinals, use the cones first, then the colour bands, then the flash mnemonic.
If those three agree, the answer is usually secure.
For lateral marks, the region only changes the colours, not the core idea: the mark still identifies the side of the channel in the conventional direction of buoyage.
Key Takeaways
North: cones up, black over yellow, continuous flashing
East: cones base-to-base, BYB, 3 flashes (3 o'clock)
South: cones down, yellow over black, 6+1 flashes (6 o'clock)
West: cones point-to-point, YBY, 9 flashes (9 o'clock)
Common Mistakes
Confusing east (3 flashes) and west (9 flashes) cardinals
Passing on the wrong side of a cardinal mark
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