Mud Seabed (M)
The code M identifies mud as the nature of the seabed.
Depths & Clearance
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Rock Seabed (R)
The code R identifies rock as the nature of the seabed or a rock feature.
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Sand Seabed (S)
The code S identifies sand as the nature of the seabed.
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Transducer Offset
A correction applied between a sensor’s physical reference point and the datum in which its displayed value is required. An echo sounder may be offset to show depth below the transducer, keel or waterline. The selected convention and sign must be documented because an incorrect offset can create a dangerous depth error.
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Taking the Ground
A vessel’s hull or keel coming into supported contact with the seabed as water level falls or by deliberate manoeuvre. Safe deliberate grounding requires suitable bottom, hull strength, predicted tide, stable attitude and protection for appendages and intakes. An unplanned grounding demands immediate assessment of damage, tide and refloating options.
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Squat
The bodily sinkage and change of trim experienced by a vessel moving through shallow or confined water. Accelerated flow around the hull lowers pressure and reduces under-keel clearance, with magnitude increasing strongly with speed and blockage. Allowance depends on hull form, water depth, channel geometry and vessel speed.
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Abbreviation | General Nautical Terminology | Nautical Topics | Depths & Clearance | Navigation | Tides
Low Water (LW)
The lowest level reached by the tide during a particular tidal cycle.
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Abbreviation | General Nautical Terminology | Nautical Topics | Depths & Clearance | Navigation | Tides
High Water (HW)
The highest level reached by the tide during a particular tidal cycle.
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Downflooding
The entry of water into normally dry spaces through openings as a vessel heels or is immersed. Open hatches, vents, doors and damaged closures can cause progressive flooding and a rapid loss of stability and reserve buoyancy. Downflooding points are therefore important in stability assessment and heavy-weather preparation.
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Downflooding Angle
The angle of heel at which water can first enter a normally dry space through a relevant opening. It limits the usable stability range even if the theoretical righting lever remains positive beyond that angle. Loading, trim, open closures and damage can reduce the angle.
If you belive the Earth is flat, you're about to fall of the end...
If you belive the Earth is flat, you're about to fall of the end...
