A cardinal mark is a sea mark (a buoy or other floating or fixed structure) used in maritime pilotage to indicate the position of a hazard and the direction of safe water.
Cardinal marks indicate the direction of safety as a cardinal (compass) direction (north, east, south or west) relative to the mark. This makes them meaningful regardless of the direction or position of the approaching vessel, in contrast to the (perhaps better-known) lateral mark system.
The characteristics and meanings of cardinal marks are as defined by the International Association of Lighthouse Authorities.
A cardinal mark indicates one of the four compass directions by:
| Characteristic | North | South | East | West |
|---|---|---|---|---|
| Topmark | ▲ ▲ Both cones point upwards | ▼ ▼ Both cones point downwards | ▲ ▼ Cones point away from each other | ▼ ▲ cones point towards each other |
| Colour | Black above yellow | Yellow above black | Yellow horizontal band on a black body | Black horizontal band on a yellow body |
| Light (if fitted) | Continuous flashes | 6 quick flashes + 1 long flash | 3 flashes | 9 flashes |
Either a quick or a very quick sequence of light flashes may be used; the choice allows for two similar nearby marks to be uniquely identified by their lights.
A cardinal mark may be used to accomplish the following:
Other uses:
The north and south topmarks are self-explanatory (both cones pointing up, or both pointing down). Remembering the east and west marks can be more of a problem.
The colours can be remembered this way: The two conical top-marks always point to black.
Seamanship is the art, knowledge and competence of operating a ship, boat or other craft on water. The Oxford Dictionary states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea."
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The four cardinal directions, or cardinal points, are the four main compass directions: north, south, east, and west, commonly denoted by their initials N, S, E, and W respectively. Relative to north, the directions east, south, and west are at 90 degree intervals in the clockwise direction.
Piloting or pilotage is the process of navigating on water or in the air using fixed points of reference on the sea or on land, usually with reference to a nautical chart or aeronautical chart to obtain a fix of the position of the vessel or aircraft with respect to a desired course or location. Horizontal fixes of position from known reference points may be obtained by sight or by radar. Vertical position may be obtained by depth sounder to determine depth of the water body below a vessel or by altimeter to determine an aircraft's altitude, from which its distance above the ground can be deduced. Piloting a vessel is usually practiced close to shore or on inland waterways. Pilotage of an aircraft is practiced under visual meteorological conditions for flight.
The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA), previously known as International Association of Lighthouse Authorities, is an intergovernmental organization founded in 1957 to collect and provide nautical expertise and advice. IALA is also known by its French name of Association Internationale de Signalisation Maritime (AISM).
A lateral buoy, lateral post or lateral mark, as defined by the International Association of Marine Aids to Navigation and Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the edge of a channel.
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A safe water mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the end of a channel. They usually imply that open, deep and safe water lies ahead. They are also used to indicate the start and end of a buoyed section of a continuous narrow channel; and a series of them may mark a safe route through shallow areas. It is therefore important to consult appropriate charts to determine their meaning in each location. They are also known as fairway buoys and clear water buoys.
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