8.2 Cardinal Marks: Quadrants, Topmarks, Colours & Light Sequences

8.2 Cardinal Marks: Quadrants, Topmarks, Colours & Light Sequences

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Principles & Purpose of Cardinal Buoyage

Unlike lateral marks, which depend on a channel's conventional direction of buoyage, Cardinal Marks are referenced to the 360-degree True compass rose. Their meaning is universal and identical in both IALA Region A and Region B.

A cardinal mark is always positioned in the quadrant corresponding to its name relative to the danger it marks:

• North Cardinal Mark: Moored to the North of the danger; safe water lies to the North of the mark; pass to the North.
• East Cardinal Mark: Moored to the East of the danger; safe water lies to the East of the mark; pass to the East.
• South Cardinal Mark: Moored to the South of the danger; safe water lies to the South of the mark; pass to the South.
• West Cardinal Mark: Moored to the West of the danger; safe water lies to the West of the mark; pass to the West.

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The Four Navigational Quadrants & True Bearings

The four quadrants are defined by True bearings taken from the center of the navigational danger:

• North Quadrant: Bounded by True bearings Northwest (315°T) through North to Northeast (045°T).
• East Quadrant: Bounded by True bearings Northeast (045°T) through East to Southeast (135°T).
• South Quadrant: Bounded by True bearings Southeast (135°T) through South to Southwest (225°T).
• West Quadrant: Bounded by True bearings Southwest (225°T) through West to Northwest (315°T).

A cardinal mark is placed within its designated quadrant. Large shoals are frequently ringed by multiple cardinal marks guarding different sectors.

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Cone Topmarks: The Master Geometric Mnemonic

All cardinal marks carry two black conical topmarks mounted vertically on a pillar or spar. The orientation of the cone points forms the definitive daymark identifying the buoy:

1. North Cardinal Topmark: $\blacktriangle \blacktriangle$

• Orientation: Both cones point UPWARDS.
• Mnemonic: Both cones point North (upward on a standard chart).

2. South Cardinal Topmark: $\blacktriangledown \blacktriangledown$

• Orientation: Both cones point DOWNWARDS.
• Mnemonic: Both cones point South (downward on a standard chart).

3. East Cardinal Topmark: $\blacktriangle \blacktriangledown$

• Orientation: Cones point away from each other (base-to-base).
• Mnemonic: Silhouette forms an egg, or the capital letter E for East.

4. West Cardinal Topmark: $\blacktriangledown \blacktriangle$

• Orientation: Cones point toward each other (apex-to-apex).
• Mnemonic: The narrow center forms a wineglass waist, resembling the letter W for West.

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Colour Patterns: Following the Points

The horizontal black and yellow bands on the buoy's hull directly reflect the direction in which the topmark cones point. Black bands sit where the cone points are located:

• North Cardinal: Both cone points point up $\rightarrow$ Black on top, Yellow on bottom.
• South Cardinal: Both cone points point down $\rightarrow$ Yellow on top, Black on bottom.
• East Cardinal: Cones point away from each other $\rightarrow$ Black at top and bottom, with a Yellow band in the middle (Black-Yellow-Black).
• West Cardinal: Cones point toward each other $\rightarrow$ Black band in the middle, with Yellow at top and bottom (Yellow-Black-Yellow).

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Light Rhythms: The Clock-Face System

When lighted, cardinal marks exhibit a white light. To distinguish quadrants at night, IALA uses the clock-face system:

Quick (Q) vs. Very Quick (VQ) Flashing

Cardinal lights flash at one of two standardized rates:

• Quick Flashing (Q): 50 or 60 flashes per minute; 60 flashes/min is one flash per second.
• Very Quick Flashing (VQ): 100 or 120 flashes per minute; 120 flashes/min is two flashes per second.

The Clock Positions

1. North Cardinal (12 o'clock): Top of the clock face. Exhibits continuous flashing without interruption (continuous Q or VQ).
2. East Cardinal (3 o'clock): At 3 o'clock on the clock face. Exhibits a group of 3 flashes:
   • VQ(3) in 5s, or Q(3) in 10s.
3. South Cardinal (6 o'clock): At 6 o'clock on the clock face. Exhibits a group of 6 flashes followed immediately by 1 Long Flash:
   • VQ(6) + LFl in 10s, or Q(6) + LFl in 15s.
4. West Cardinal (9 o'clock): At 9 o'clock on the clock face. Exhibits a group of 9 flashes:
   • VQ(9) in 10s, or Q(9) in 15s.

The Critical Role of the Long Flash on a South Cardinal

A long flash (LFl) has a light duration of not less than 2.0 seconds. In rough seas, vessel motion makes counting rapid flashes difficult. A mariner might miscount five or seven flashes for six. The unmistakable two-second sustained beam positively confirms that the buoy is a South Cardinal and prevents confusion with a 3-flash East or 9-flash West mark.

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Practical Seamanship, Night Pilotage & Exam Traps

1. Stopwatch Timing: Never guess a cardinal light at night. Time the sequence with a stopwatch to count flashes and measure the total cycle period in seconds.
2. Safe Stand-off Margin: A cardinal mark does not specify a safe passing distance or guarantee depth. Check the charted danger extent and soundings, and choose a clearance appropriate to the vessel and conditions.
3. Tidal Stream Set: When passing a cardinal mark, verify tidal stream direction. A cross-stream setting toward the hazard requires laying off a counteracting heading.
4. Daylight Silhouette Identification: When looking into the sun or at twilight, black and yellow paint appears uniformly dark. Identify the aid strictly by its cone silhouettes.