Cardinal mark

In maritime pilotage, a cardinal mark is a buoy or fixed structure indicating the safest side to pass a navigational hazard. The name “cardinal” refers to the four cardinal compass points: North, East, South, and West. Each mark’s design, colours, topmark shape, and light characteristic uniquely identify the quadrant of safe water.

For instance, a North cardinal mark signals that safe water lies to its north; pass north of it. An East mark says safe water is east, so go east of it – and similarly for South and West. The topmarks consist of two black cones. North: both point up. East: base‑to‑base (hourglass). South: both point down. West: point‑to‑point (diamond). The colour pattern: North black above yellow; East black‑yellow‑yellow‑black; South yellow above black; West yellow‑black‑yellow.

Lights are white and flash in quick (Q, 50–60 flashes per minute) or very quick (VQ, 100–120 flashes per minute) rhythms. North: continuous Q or VQ. East: three flashes (Q(3) 5s or VQ(3) 5s). South: six flashes plus a long flash (Q(6)+LFl 15s or VQ(6)+LFl 10s). West: nine flashes (Q(9) 15s or VQ(9) 10s).

Always use a marine compass to take a bearing and confirm the mark’s quadrant. Modern GPS navigation can locate the mark on a chartplotter, but visual identification remains essential, especially when electronics fail or in poor visibility.