Buoys Part II: The Cardinal Rule

Boaters growing up sailing in the United States who still spend their time solely in U.S. waters face two navigational quandaries. First, we are metrically challenged. As long as our charts display soundings in ‘feet’ and not ‘meters’, we are in our comfort zone. Also, if our aids to navigation are lateral and Red-Right-Returning, our anxiety levels are kept in check.

However, once we wander afar and sail the Caribbean or the Med, we become perplexed when we come upon a yellow and black buoy with two black conical topmarks. Quickly turning to our well-worn volume of Chapman’s Seamanship, we discover a confusing diagram with four yellow and black-banded buoys surrounding what is euphemistically called a ‘point of interest’.

The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) prescribes cardinal marks as a method for maritime countries around the world to indicate the position of a hazard and the direction of safe water for vessels to avoid that danger.

Cardinal has many definitions: a leading dignitary in the Roman Catholic Church, a red song bird and a player on a St. Louis baseball team. But a lesser-known definition is the four major directions of a compass: north, south, east, and west.

Substitute the word ‘danger’ for ‘point of interest’ in the diagram, and the use of cardinal marks becomes clearer. Always leave the cardinal mark between your boat and the danger, while passing that danger toward the direction indicated by buoy to find the best navigable water. According to The Mariner’s Handbook, published by the United Kingdom’s Hydrographic Office, Cardinal marks may by used to indicate that the deepest water in an area is on the named side of the mark; indicate the safe side on which to pass a danger; (or) draw attention to a feature in a channel such as a bend, junction, bifurcation, or end of a shoal.

If fitted with two black triangular topmarks, the orientation of the topmarks indicates the cardinal point of the compass. Two triangles apexes pointing up means pass to the north. Two triangles apexes pointing down means pass to the south. Two triangles apexes pointing apart pass to the east. And two triangles apexes pointing together pass to the west. To memorize these orientations is straight forward, north and south point up and down respectively, as those directions do on a compass rose. The topmarks denoting east and west ‘follow the Sun’. The top cone points in the direction the Sun is moving with respect to the horizon, that is, rising for an east mark and setting for a west mark.

The distinctive yellow and black bands also indicate compass direction: black on top is north, black on the bottom is south, black in the middle of two yellow stripes is west and yellow in the middle of two black stripes is east. Another way of looking at it is that the black cones on the topmark point to the black stripes on the buoy.

If a cardinal marks is lit, the light is always white but the flashes can be quick or very quick. The pattern of flashes mimics that of an analog clock face. Imagine a compass rose as a clock. East would be three o’clock, south would be six o’clock, west would be nine o’clock and north would be twelve o’clock. An east mark flashes three white, a south mark flashes six white followed by one long flash, the west mark flashes nine white and the north mark flashes continuously.

It would be nice to have the United States adopt the usage of cardinal marks. But then again, my first grade teacher assured me by the time I was thirteen years of age our country would have ‘gone metric’. That was five decades ago, and I am still holding my breath.

Capt. Jeff Werner is a 23 year veteran of the yachting industry. In addition to working as a captain on private and charter yachts, both sail and power, he is a certified instructor for the RYA, MCA, USCG and US Sailing.

Frequently Asked Questions About Cardinal Marks

What is a cardinal mark?

A cardinal mark is a navigation buoy that indicates the location of a hazard and the direction of safe water relative to that hazard. They are used throughout much of the world under the IALA buoyage system.

How do cardinal marks differ from lateral marks?

Lateral marks identify the sides of a channel, such as the familiar Red-Right-Returning system used in the United States. Cardinal marks, by contrast, identify the safest direction to pass a danger.

What do the four cardinal marks mean?

• North Cardinal: Safe water lies to the north.
• East Cardinal: Safe water lies to the east.
• South Cardinal: Safe water lies to the south.
• West Cardinal: Safe water lies to the west.

How do I identify a cardinal mark?

Cardinal marks are identified by:

• Black and yellow horizontal bands
• Two black conical topmarks
• Distinctive white light flash patterns when illuminated

The position of the black bands and cones indicates the cardinal direction.

How do the topmarks work?

The two black cones point toward the black section of the buoy:

• Both cones pointing up = North
• Both cones pointing down = South
• Cones pointing apart = East
• Cones pointing together = West

What do the buoy colors mean?

The color pattern corresponds to the cardinal direction:

• Black over yellow = North
• Yellow over black = South
• Black-yellow-black = West
• Yellow-black-yellow = East

What light patterns do cardinal marks use?

All cardinal marks display white lights. However, each uses a unique flashing sequence:

• North: Continuous quick flashes
• East: Three flashes
• South: Six flashes followed by one long flash
• West: Nine flashes

The flash counts correspond to positions on a clock face.

Are cardinal marks used in the Caribbean?

Yes. Many Caribbean nations use the IALA buoyage system and employ cardinal marks to identify reefs, shoals, wrecks, and other navigational hazards.

What is the easiest way to remember cardinal marks?

Remember that the cones point toward the black section of the buoy. Also, think of the east and west cones as following the sun—rising in the east and setting in the west.

---

What This Means

Cardinal marks may look intimidating at first. However, they provide one of the most effective systems for identifying hazards and locating safe water.

• They indicate safe water, not channel edges
• The topmarks reveal direction at a glance
• The color bands reinforce the message
• The light patterns provide confirmation at night

For cruisers venturing beyond U.S. waters, understanding cardinal marks is an essential navigational skill.

Capt. Jeff Werner has written for ALL AT SEA since 2014.