- Lateral mark
buoy, lateral post or lateral mark, as defined by the International Association of Lighthouse Authorities, is a sea markused in maritime pilotageto indicate the edge of a channel.
Each mark indicates the edge of the safe water channel in terms of port (left-hand) or
starboard(right-hand). These directions are relative to the "direction of buoyage"; this is usually a nominally upstreamdirection. In a river, the direction of buoyage is towards the river's source; in a harbour, the direction of buoyage is into the harbour from the sea. Where there may be doubt, it will be labelled on the appropriate chart.
A vessel heading in the direction of buoyage (eg into a harbour) and wishing to keep in the main channel should:
* keep port marks to its port (left), and
starboardmarks to its right.
Marks are distinguished by their colour, being red or green, and shape.
For historical reasons, two different schemes are in use worldwide, differing in their use of colour.
Previously there had been 30 different buoyage systems, prior to IALA introducing the rationalised system.
The IALA defines them as System A and System B:
* System A is used by nations in
Europe, Australia, New Zealand, parts of Africaand most of Asiaother than the Philippines, Japan and Korea.
* System B is used by nations in
North America, Central Americaand South America, the Philippines, Japanand Korea.
* port marks are red and may have a red flashing light.
* starboard marks are green and may have a green flashing light.
(Port) (left) (Red) _____________________________________ (Starboard) (right) (Green)
* port marks are green, and may have a green flashing light.
* starboard marks are red and may have a red flashing light.
(Port) (left) (Green) _____________________________________ (Starboard) (right) (Red)
* port marks are square or have a flat top
* starboard marks are conical (or present a triangular shape) or have a pointed top.
The shape is an important feature, as colours cannot be distinguished in some light conditions, or by persons with red-green
colour blindness. Marks may also carry unique markings of letters and numbers; these may be used to identify the mark as one indicated on a nautical chart. Likewise, a mark's light may flash in a distinctive sequence for the same purpose.
Also defined in the lateral mark systems is a "bifurcation" mark, which has both red and green horizontal bands, one over the other. This mark indicates that a "preferred" channel (often, a deep channel suitable for heavy commercial traffic) lies to one side, and a secondary channel on the other. Vessels wishing to use the preferred channel observe the top colour of the mark, and vessels wishing to use the secondary channel observe the bottom colour.
In System A only, the phrase "Is there any red port left?" (referring to the red colour of the fortified wine "port") may be used as a mnemonic, indicating that a red mark must be kept on the left when "returning" to (i.e, entering) a harbour or river.
In System B only, the phrase "red right returning" may be used as a mnemonic, indicating that a red mark must be kept on the right when "returning" to ("i.e.", entering) a harbour or river.
The alternative system of
cardinal marks is used where there is no clear upstream reference direction.
* A [http://www.tc.gc.ca/marinesafety/Tp/tp14070/b3-buoys.htm web site of Transport Canada] , showing lateral marks in System B.
Safe water mark
Isolated danger mark
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