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Graphical and textual descriptions of navigational light sequences and colours are displayed on nautical charts and in Light Lists with the chart symbol for a lighthouse, lightvessel, buoy or sea mark with a light on it. Different lights use different colours, frequencies and light patterns, so mariners can identify which light they are seeing. [1]
Marks are shown on nautical charts, using symbols that indicate their colour, shape and light characteristic, and are usually identified by name or number. In a wider sense the phrase "sea mark" is often understood to include all types of landmarks, structures and devices that can be used to provide warning and guiding signs to mariners.
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. [1] 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.
A cardinal mark is a sea mark (a buoy or other floating or fixed structure) commonly 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.
[1] IALA divides the world into two regions: A and B. Region B is the Americas (excluding Greenland) along with Japan, Korea and the Philippines. Region A is the rest of the world. In region A port marks are red and starboard marks green. In region B port marks are green and starboard red. [1]
The buoy where the channels divide would be a red cylindrical can or pillar with a cylindrical top mark. Around the middle would be a green band. In IALA region B the shape would be identical, but the main colour would be green with a red band. [4] See the buoy by the island in the diagram above.
A signboard identifying it is called a day mark. [1] Day beacons typically mark channels whose key points are marked by lighted buoys. They may also mark smaller navigable routes in their entirety. They are the most common navigation aid in shallow water, as they are relatively inexpensive to install and maintain.
The buoy is expected to be deployed for the first 24-72 hours after the wreck occurs. After that time more permanent buoyage (such as isolated danger marks or cardinal marks) should be deployed and charts updated. [1] The buoy is designed to "provide a clear and unambiguous" [1] mark of a new and uncharted danger. The buoy is painted with 4, 6 ...