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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About Author
Subhodeep is a Naval Architecture and Ocean Engineering graduate. Interested in the intricacies of marine structures and goal-based design aspects, he is dedicated to sharing and propagation of common technical knowledge within this sector, which, at this very moment, requires a turnabout to flourish back to its old glory.
Disclaimer :
The information contained in this website is for general information purposes only. While we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information, products, services, or related graphics contained on the website for any purpose. Any reliance you place on such information is therefore strictly at your own risk.
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