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What Are Isolated Danger Marks?
We have lights, markers, and signage to indicate traffic conditions and measures to ensure safety on the roads. Similarly, the International Association of Marine Aid to Navigation and Lighthouse Authorities (IALA) defines a system of markings and indicators to ascertain best practices for ship navigability in the waters.
Sea marks are a system of markers that help seafarers identify potential hazards, roadblocks, situations, requirements, and instructions that must be followed in their navigational course. These seamarks are of various types and appearances, following a sign convention based on the designated purpose.
In this article, we will discuss a specific type of sea mark known as an isolated danger mark.
As the name suggests, an isolated danger mark is a sea mark employed to identify a specific hazard under the water that is not visible to a seafarer or navigator.
These include submerged wrecks or objects, rocks, boulders, reefs, shoals, and other underwater geographical features, such as a subsea hill or ridge that tips dangerously close to the waterline.
By looking at an isolated danger mark, a seafarer needs to take preventive actions like steering the vessel away from the trajectory that has the hazard in its projected course and ply not over or even too close such that any form of underwater presence does not cause incidents like grounding or breach in the hull due to impact from the bottom.
The isolated danger mark appears as a cylindrical or conical structure characteristic of alternating black and red stripes mounted atop a floating buoy, spar, or a fixed structure. The number of red stripes can be one or multiple.
Atop the pillar or cylindrical or conical structure are two black spherical balls mounted one above the top of the other.
At night, the red stripes glow in the dark due to iridescence and can be easily spotted by a passing ship. However, the most distinguishing and reliable feature for identifying an isolated danger mark at night is a flashing white light beacon at the top of the marker.
The light flashes in groups of two at 5 to 10 seconds. When you spot an isolated danger mark, the beacon or flashlight flashes twice successively and remains dormant for about 5 to 10 seconds before flashing twice again.
As per regulations, the two black spheres at the top of an isolated danger mark should be constructed to be visible, and the separation between the two should be distinct.
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Disclaimer :
The information on this website is for general purposes only. While efforts are made to ensure accuracy, we make no warranties of any kind regarding completeness, reliability, or suitability. Any reliance you place on such information is at your own risk. We are not liable for any loss or damage arising from the use of this website.
About Author
Subhodeep is a Graduate of Naval Architecture and Ocean Engineering. He has deep interest in marine structures and goal-based design aspects, and is dedicated to sharing and propagating technical knowledge of the industry.
Disclaimer :
The information on this website is for general purposes only. While efforts are made to ensure accuracy, we make no warranties of any kind regarding completeness, reliability, or suitability. Any reliance you place on such information is at your own risk. We are not liable for any loss or damage arising from the use of this website.
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