Navigating Lateral and Cardinal Marks

15th March 2017

Navigating the channels, seas and waterways of the world can be a tricky business but ever since man took to the seas there has been a correlative system of piloting aids; from the fire and mirror lighthouses of Ancient Egypt to the complex system of buoys, marks and posts used in modern seafaring.

These important markers are crucial in assisting with the safe passage of vessels in narrow or busy channels, harbours and waterways. Even in an age with advanced technological navigational systems, the use of buoys as visual indicators is as important today as it’s always been. In this guide, we take a look at the different types of sea marks in use, the history of why there are two different regional schemes in operation internationally and the detail of the seamarks in use.

Seamark Systems (pre-1976)

Historically, the systems of seamarks used by different nations developed independently of any international accord with each country adopting a slightly different approach. Naturally, as vessels moved across international waters there was considerable confusion. As commercial shipping began to become more globalised (and, as a result, busier) during the 19th century, the need for an international standard became more obvious.

Taking almost 100 years to standardise, it was the British Maritime Safety Authority, Trinity House, who first called for an agreement on the uniformity of global buoyage.

In 1882, the UK called for a meeting of minds on the matter but it wasn’t until 1889 that an international conference was finally arranged. Taking place in Washington DC, most of Trinity House’s global counterparts attended and a uniform system was eventually agreed upon. Taking the form of a lateral (or side-marking) system, the standard (at the time) was proposed to be:

  • Starboard buoys (going with the main tidal flood system or the right hand side of a ship entering from seaward) would be conical and black;
  • Port buoys would be red (or chequered) and be a truncated cone in shape.

At the time, no agreement could be made on how to mark the middle ground; though the prevailing British way of doing this was in the form of spherical buoys.

In 1912, a second conference took place in St Petersburg largely attempting to address the concerns of those nations bordering the Baltic Sea. The system established in Washington (now referred to as the ‘Lateral Mark’ system) was found not be a practical in their waters. Agreement was therefore reached to adopt a separate system, called the Cardinal (or Directional) System. Based on a combination of colours and shapes plus compass quadrants on a buoy’s topmark relating to the hazard it marked, this new method was referred to as the ‘Cardinal Mark System’. It was adopted as an exclusive method by Norway, Sweden and Russia with Italy, Germany and Turkey using a combination of both the Lateral and Cardinal system.

With some countries failing to adopt either system, others conforming to one or a combination of the old or new, the attempts to produce a single international standard were not working and until 1976 up to thirty different methods of buoyage were in use.

It was a series of collisions in the Dover Strait during 1971, a few of which resulted in fatalities, that prompted authorities across the world to focus their attention on a new international effort to standardise these important navigational aids.

Following the incidences of 1971, the IALA (International Association of Lighthouse Authorities) began implementing what is now known as the IALA Maritime Buoyage System.

The IALA Maritime Buoyage System

Operating in two different regions, the IALA Maritime Buoyage System uses five different types of marks to assist in the safe pilotage of vessels at sea, namely:

  • Lateral Marks – marking the edge of channels
  • Cardinal Marks – marking the position of hazards and the direction of navigable waters
  • Isolated Danger Marks – marking out shipping hazards
  • Safe Water Marks – marking the end of a channel and indicating deep safe water ahead
  • Special Marks – marking a feature or area such as mooring or speed restrictions.
Two Different Regions

With the exception of Lateral Marks, all marks are common to the two different regions. Known as Region A and Region B, these separate global areas were defined as a compromise to help standardise a buoyage system that suited all geographical locations. The regions are broadly split longitudinally with the exception of a handful of Asian countries occurring in Region A.

  • Region A covers Europe, the Gulf, Australia, New Zealand and Africa with some Asian countries
  • Region B covers Central and South America, Japan, the Philippines, North and South Korea.
Lateral Marks

These marks are used to define routes and channels in waterways such as harbours or estuaries and marked from a seaward direction. Vessels should keep port marks to the left and starboard marks to the right.

Where a channel separates, a preferred route is marked using a variation of banded lateral marks. A preferred channel is usually chosen due to the presence of deeper water.

Region A

Port Hand Mark (REGION A)

Coloured red, these marks are cylindrical or pillar shaped and fitted with a matching red can topmark; where fitted, lights are also red. Lights can flash in any rhythm, with the exception of 2+1

Starboard Hand Mark (REGION A)

Coloured green, these marks are cylindrical or pillar shaped and fitted with a matching red cone topmark that points upwards; where fitted, lights are also green. Lights can flash in any rhythm, with the exception of 2+1.

Preferred Route to Port (REGION A)

Preferred routes are indicated using a green cone, pillar or spur but will have a single red, horizontal band around the buoy. Where fitted, lights will be green and can flash in any rhythm with the exception of 2+1.

Preferred Route to Starboard (REGION A)

Preferred routes are indicated using a red cone, pillar or spur but will have a single green, horizontal band around the buoy. Where fitted, lights will be red and can flash in any rhythm with the exception of 2+1.

Region B

Port Hand Mark (REGION B)

Coloured green, these marks are cylindrical or pillar shaped and fitted with a matching red cone topmark that points upwards; where fitted, lights are also green. Lights can flash in any rhythm, with the exception of 2+1.

Starboard Hand Mark (REGION B)

Coloured red, these marks are cylindrical or pillar shaped and fitted with a matching red can topmark; where fitted, lights are also red. Lights can flash in any rhythm, with the exception of 2+1

Preferred Route to Port (REGION B)

Preferred routes are indicated using a red cone, pillar or spur but will have a single green, horizontal band around the buoy. Where fitted, lights will be red and can flash in any rhythm with the exception of 2+1.

Preferred Route to Starboard (REGION B)

Preferred routes are indicated using a green cone, pillar or spur but will have a single red, horizontal band around the buoy. Where fitted, lights will be green and can flash in any rhythm with the exception of 2+1.

Cardinal Marks

Cardinal marks are used to identify the safest water to pilot around a hazard. They indicate the direction of safety using a compass system relative to the point of the mark. They are therefore meaningful whichever direction you are approaching them.

Identified by their yellow and black marks, they are used to signify the safest route past a danger, the presence of the deepest water or to identify a feature in a channel such as a junction, end of a shoal or bend.

North Cardinal Mark

Black above yellow, the north cardinal mark has 2 upwardly pointed black cones for a topmark and is shaped like a pillar or spur.

Lights, where fitted, are white and flash in a Q (50-60 flashes per minute) or VQ (100-120 flashes per minute) rhythm.

South Cardinal Mark

Yellow above black, the south cardinal mark has 2 downwardly pointed black cones for a topmark and is shaped like a pillar or spur.

Lights, where fitted, are white and flash in a Q (50-60 flashes per minute) + long flash every 15 seconds or VQ (100-120 flashes per minute) + long flash every 10 seconds rhythm.

East Cardinal Mark

Black with a single broad horizontal yellow band, the east cardinal mark has 2 black cones for a topmark, one pointing up and one pointing down (base to base) and is shaped like a pillar or spur.

Lights, where fitted, are white and flash in a Q (50-60 flashes per minute) every 5 seconds or VQ (100-120 flashes per minute) every 10 seconds rhythm.

West Cardinal Mark

Yellow with a single broad horizontal black band, the west cardinal mark has 2 black cones for a topmark, one pointing up and one pointing down (point to point) and is shaped like a pillar or spur.

Lights, where fitted, are white and flash in a Q (50-60 flashes per minute) every 10 seconds or VQ (100-120 flashes per minute) every 15 seconds rhythm.

Isolated Danger Marks

A black buoy with one or more horizontal red bands, the isolated danger marks have two spherical topmarks. Where fitted, white lights pulse in a group flash (2). Though they can be of any shape, they are preferred to be conical or cylindrical.

They are moored or erected directly above a hazard such as a wreck or submerged rock but navigable and safe water can be found all around the direct mark.

Safe Water Marks

Marked with distinctive vertical red and white stripes, safe water marks can be spherical or pillar/spar shaped with a spherical topmark. Lights (where fitted) are white and flash in an occulting isophase rhythm (one long flash every 10 seconds – Morse “A”).

These marks indicate that the water around it is safe and is navigable. They do not denote danger and are the only marks to have vertical stripes.

Special Marks

Though not used as a primary safety or navigational buoy, special marks are useful to signify areas of note such as the presence of cables and pipes, moorings, speed limits or recreational zones. They are yellow in colour and can be of any shape with St Andrew’s Cross as a top mark (where fitted).

Yellow lights can flash in any rhythm other than those used in Cardinal, Isolated Danger or Safe Water marks.

For more information, the Symbols and Abbreviations Guide (published by Admiralty Hydrographic Office) is a useful aid or, for a more concise aid, Reeds Skipper’s Handbook.


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