Club Marine eNews

Navigational marks and what they mean

Navigational marks
Each mark in the buoyage system plays a part in guiding mariners safely or alerting them to dangers or special areas on the coastline and in enclosed waters.

In Australia and New Zealand, the international IALA A buoyage system is used (IALA B is used in the Americas, Japan, Korea and the Philippines). It was devised by the International Association of Lighthouse Authorities (IALA) and introduced in the 1980s to provide a uniform buoyage system worldwide.

There are six categories of marks, commonly called navigation marks or navigation beacons. They each have a unique colour or combination of colours, and may be fitted with a top mark or shape to identify them. If lit at night, they’ll have a unique light colour or flashing sequence.

Navigation marks are shown as symbols on charts and chartplotters, and may differ depending on the chart’s format. Typically, electronic chartplotters will show them in full colour, whereas on official paper charts they’re black with the top mark displayed and the colour described by a letter underneath the symbol.

Remember to always check a chart/chartplotter or have local knowledge of the waterway to be assured there is sufficient water depth for your boat, even when navigation marks indicate safe passage.

LATERAL MARKSNavigational marks lateral

  • Lateral marks are used to indicate the lateral limits of safe water or the sides of a channel. There are two lateral marks: port (red/left) and starboard (green/right).
  • In the IALA A buoyage system, the direction of lateral buoyage is inwards or ‘going upstream’ and, logically, is reversed when heading downstream.
  • Port marks are passed on your left-hand side and starboard marks on your right-hand side when going upstream or into a port. If you are coming downstream, they are the opposite way around.
  • A way to remember this is an old sailor’s saying: ‘is there any red port left’ when heading upstream.
  • Port marks are red, have a red light (if fitted) and a can-shaped top mark.
  • Starboard marks are green, have a green light (if fitted) and a cone or triangular-shaped top mark.
Textbooks will often show port and starboard marks opposite each other in neat rows, but this is not always the case – you may see single beacons marking channels, or a corresponding opposite mark could be miles on the other side of a large bay or estuaries. It’s recommended to take each mark one at a time and check a chart or chartplotter to clarify the situation.

ISOLATED DANGER MARKSNavigational marks isolated & special
  • Isolated danger marks are used to mark hazards or dangers to safe navigation and are located on, or moored above, an isolated danger of limited extent.
  • They have red and black horizontal bands with two black spheres as a top mark. If they have a light, it is white and flashes in groups of two.
  • An easy way to remember them is ‘black and red, there’s danger ahead’.
  • The water around the mark is navigable, but there is no general rule as to how far the danger may extend. This can vary markedly, so always check a chart/chartplotter.

  • Special marks are used in a variety of situations – typical uses include marking aquaculture areas, pipelines, no-boating zones, historic shipwrecks, marine parks, and the bifurcation (or junctions) in boat channels.
  • Quite often, special marks will have a name on them indicating what they are.
  • Special marks are yellow, with a yellow cross as the top mark. If lit, the light is yellow and can have various flashing sequences.

CARDINAL MARKSNavigational marks cardinal
  • Cardinal marks indicate the direction of the deepest water from the mark. So named because they refer to the cardinal points of the compass: north, south, east and west.
  • To use them, you have to know the direction of north.
  • Cardinal marks have combinations of yellow and black bands and have two black cone-shaped top marks in various configurations. The black bands are found in the direction of where the cones point.
  • North cardinal marks indicate the deepest water is found in the north quadrant from the mark – from north east to north west.
  • The cones point upward, and the mark is yellow on the bottom with the black band at the top.
  • East cardinal marks indicate the deepest water is in the east quadrant from the mark – from the north east to south east.
  • The cones face away from each other, and the mark has a black band top and bottom with a yellow band in the centre.
  • South cardinal marks indicate the deepest water is in the southern quadrant of the mark, from south east to south west.
  • Both black cones point down, and the bands are black on the bottom and yellow at the top.
  • West cardinal marks indicate the deepest water is in the west quadrant – south west to north west.
  • The black cones point inward, and the mark is yellow on the bottom and top and black in the middle.
An easy way to recognise them by day is to use their top marks – on north marks the cones point upwards and on south marks they point downwards, while east mark cones point away from each other (they look a little like an egg – E), and west mark cones point inwards to each other (they look like a W on its side).

If the marks are lit at night, the lights’ flash sequences follow a clock face: north is continuous flashing, east has three flashes (3 o’clock), south has six flashes followed by a long flash (6 o’clock), and west has nine flashes (9 o’clock).

The lights are normally white, but a blue light can be used if there’s back lighting.

Some cardinal marks have blue reflective strips so they can be identified by shining a spotlight on them.

Generally, just one or two cardinal marks are used, not all four. When unfamiliar with the area, stop and assess how to best proceed.

SAFE-WATER, EMERGENCY AND OTHER MARKSNavigational marks Safe water and emergency wreck
Safe-water marks generally mark the start of a channel or landfall. They have red and white vertical stripes and show a white light of equal light and dark at night. The water around is navigable.

Emergency marks are used to mark newly discovered dangers that are yet to be included in nautical publications and charts. The mark has yellow and blue vertical stripes and an upright yellow cross top mark. They show a light that alternates between yellow and blue. The marks are placed as close as possible to the danger.

Navigational marks leading lights transit marks
Leading lights – while not part of the IALA system, leading lights (also called transit marks or range marks) indicate a safe passage for vessels entering a narrow channel.

Typically, they’re a pair of brightly painted triangular beacons that are lit at night and separated by distance – one in the front pointing up and the other farther behind pointing down. When the points (or lights, at night) are lined up with one above the other, they provide a safe leading line to follow. Move the boat onto the leading line by steering towards the bottom mark. If it is off to the right, then steer right until they are aligned and vice versa.

Taken from Doug King’s Waterwise feature in 34.4 August/September Club Marine Magazine.