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Sailing along coasts and in estuaries requires an understanding of the IALA Buoyage System. This aid to navigation is the system of buoys and other markers identifying features such as channels or obstructions. Two [ IALA buoyage systems ] Lateral A and Lateral B were adopted in 1976 by the International Association of Lighthouse Authorities (IALA) and implemented in 1990 worldwide. Lateral A is the standard used in the British Isles, Europe, Australia, New Zealand, Africa and most of Asia, including India while the Lateral B standard operates in North, Central and South America, Japan, South Korea and the Philippines.
Marking the sides of shallow, winding channels was required early on in sailing. The original buoyage system were markers
comprising of sticks, tree branches or floating barrels, but a more sophisticated aid to navigation was needed when larger vessels required access to inland ports.
The marker colour coding system of red for port (left) and green for starboard (right) was implemented worldwide. Europe had the channels marked for a ship coming into port while in America the system conformed to the port/starboard colouring as the ship left port. These different lateral systems operate successfully and confusion only arises when sailing from one system into a country using the other, or where there is neither system.
Where there is an island close off the mainland, the 'direction' of buoyage is determined by the direction in which the flood tide flows. Where two tides meet, the IALA buoyage system direction changes at a determined point, and marked on charts.
- [ Lateral A ] system has red flat-topped cairns to port on entering, and green conical marks to starboard.
- [ Lateral B ] has green flat-topped marks to port on entering and red conical marks to starboard.
- With both systems, the buoys and markers may or may not have lights mounted on them.
The edges of channels are indicated with lateral marker buoys and channel markers and are arranged according to the direction of buoyage. Lateral marker buoys and channel markers are often [ numbered ], starting from seaward with even numbers on red marks and odd numbers on green marks. Where a channel divides, preferred channel marks which are modified lateral marks, indicate the main channel.
IALA buoyage system around coastlines is typically arranged in a clockwise direction. Check the maritime chart if the direction of IALA buoyage is not obvious and will be marked using an [ arrow with two dots ].
The [ Cardinal System ] of buoys has been universally adopted in conjunction with the lateral system. Large or individual hazards are designated with cardinal marks. Named after the points of the compass, they indicate which side to pass by them to avoid the danger, i.e. keep to the north of a north cardinal and south of a south cardinal.
Being pillar or spar shaped they are painted black and yellow. All have two black cones on the top variously arranged one above the other along with white flashing lights that flash in a sequence indicating which quadrant they sit in. In principle, minor estuarial channels are marked with the lateral system and the approaches and major obstructions are marked with the cardinal system.
The top marks of cardinal buoys consist of the combination of two black cones, mounted one above the other on the top of the buoy with the following combinations:
- Both cones pointing up = north cardinal;
- Both pointing down = south cardinal;
- One pointing up and the other down with their bases together = east cardinal; and
- One pointing up and the other pointing down with their points together = west cardinal.
If there is confusion between east and west cardinals, think of the (w)est as being (w)aisted.
- North is a black pillar on a yellow buoy;
- South is a yellow pillar on a black buoy;
- East is a black and yellow pillar on a black buoy, and
- West a yellow and black pillar on a yellow buoy.
The colours can be confusing, when weed or bird fouling occurs, and recognizing the colour of the buoy as yellow signifies north or west and a black buoy as south or east, while identifying the top mark positively, ensures that no fouling confuses the issue.
Three additional types of mark in the IALA systems are the:
- Isolated danger mark;
- The safe water mark;
- The special mark.
An [ isolated danger mark ] is used to indicate a small, solitary danger with safe water all around.
An isolated danger can be a rock or a sunken boat. The marker has horizontal black and red bands and two black spheres on top.
A [ safe water mark ] is used for mid-channel or landfall marks. It indicates safe water all around the position. The safe water mark is a spherical buoy, or a pillar or spar, with vertical red and white stripes and with a red ball on top.
[ Special Marks ] which zone off recreational areas, such as water ski areas are yellow and may have an X-shaped top mark or any shape preventing them being confused with a navigational mark. They are not primarily intended to assist in marine navigation and where cones, cans, or spheres are used, they show the side on which to pass.
Marine navigation using lights that [ identify buoys ], shore beacons, leading marks, and lighthouses make marine navigation at night possible. Buoys are lit with short-range lights and medium-range lights on shore beacons while long-range lights are used on lighthouses. There may be difficulty in identifying marks at night in the vicinity of ordinary shore lights.
To differentiate between shore lights, different lighting characteristics are used for specific marks to aid in identification. The light characteristic of each mark is noted on the chart of the area and in sailing directions. Usually, lights are white, red, green, or yellow, but purple, blue, and orange may also be used.
In addition to the light’s colour, a flashing pattern and time taken to complete the sequence is used to identifying buoys. To ensure that the mark has been correctly identified, check the timing of the flashing through three full sequences.
Prior to entering a channel, be familiar with the abbreviations and the patterns associated with the IALA buoyage system on the chosen passage. Terms used on charts are:
When approaching a harbor at night with many shore lights, it can be difficult to pick out the next buoy in the sequence. A [ hand bearing compass ] sighted along the expected bearing of the buoy may make it easier to find. Do not assume the light seen is the expected one as the boat’s position may be miscalculated so double-check.
Lighthouses, and other beacons, use coloured sector lights indicating safe and dangerous areas. The chart shows details of the colours and sector angles. The edges of the sectors are given in pilot books as bearings, and are always from seaward towards the lighthouse in degrees true (°T).