Lesson previewWhat A Cardinal Mark Says1 section shown
Preview lesson
What A Cardinal Mark Says
What you will learn
State the named compass side on which safer water lies relative to a cardinal mark's point of interest, then identify what the current chart and vessel plan must still establish.
A cardinal mark names the compass side on which safer navigable water lies in relation to a danger or other point of interest; it does not certify a complete route.
The cardinal name is an instruction about relationship. Safer navigable water lies north of a north cardinal, east of an east cardinal, south of a south cardinal and west of a west cardinal. The reference is the compass, not the side of the vessel or its present heading.
IALA describes the relationship to a point of interest. That point may be a shoal, wreck, obstruction, end of a shoal, bend, junction or fork. The current chart shows what is being marked and how the cardinal fits the surrounding route; the buoy alone cannot draw the danger's full outline.
The named side is the side on which the mark should be passed for the stated relationship. It is not an instruction to pass close, a promise of uniform depth or proof that every other compass side is unusable. IALA notes, for example, that a north cardinal can have navigable water east and west as well; consult the relevant chart.
Turn recognition into a vessel decision by checking position, danger extent, soundings, tide or water level where relevant, traffic, weather, local directions and an adequate margin. A correct mark name is the start of that decision, not its completion.
| Mark name | Governing relationship | Still establish from the navigation picture |
|---|---|---|
| North cardinal mark | Pass north of the mark; safe water lies to the north. | Point of interest, danger extent, usable depth, traffic and vessel margin |
| East cardinal mark | Pass east of the mark; safe water lies to the east. | Point of interest, danger extent, usable depth, traffic and vessel margin |
| South cardinal mark | Pass south of the mark; safe water lies to the south. | Point of interest, danger extent, usable depth, traffic and vessel margin |
| West cardinal mark | Pass west of the mark; safe water lies to the west. | Point of interest, danger extent, usable depth, traffic and vessel margin |
Interpret a north cardinal beside a shoal
A north cardinal is charted off the northern end of a shoal. The boat is south-east of the mark, a deep-draught vessel is approaching from the west and the chart shows a wider northern route.
1. Name the relationship
Safer water in relation to the marked shoal lies north of the north cardinal.
2. Locate the point of interest
Use the current chart and position to understand the shoal's extent rather than treating the buoy as its exact edge.
3. Build the route
Check depth, traffic, sea room and the vessel's turn before selecting a northern track with an appropriate margin.
4. Monitor the evidence
Confirm depth trend, position, the next aid and the approaching vessel after the manoeuvre begins.
Sense check: A plan that says only 'pass north' has not yet located the shoal, chosen a safe margin or accounted for traffic.
Common mistake or limitation
- Treating north, east, south or west as the side of the cockpit rather than a compass relationship to the mark.
- Assuming the buoy is the exact boundary of the danger and planning to pass unnecessarily close.
- Treating the named side as guaranteed depth without checking the chart, position and vessel requirements.
Recap
- Pass a cardinal mark on its named compass side for the stated safer-water relationship.
- Use the chart to identify the point of interest, danger extent and possible route.
- Depth, traffic, conditions and vessel margin still govern the actual track.
Optional quick check
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