Glossary
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TermDefinition
- General Nautical Terminology Directional LightA light illuminating a sector or very narrow angle and intended to mark a direction to be followed.
- General Nautical Terminology, Navigation Direction of Buoyage
The direction in which lateral marks (port and starboard buoys) should be passed when entering a harbour or following a main channel, based on...
More Details - General Nautical Terminology, Parts of a Boat Displacement
The weight of the water a vessel displaces when it is floating, which is equal to the vessel's own weight.
Displacement is a fundamental...
More Details - General Nautical Terminology, Parts of a Boat Displacement Vessel
A type of watercraft designed to move through the water by displacing an amount of water equal to its own weight, relying on buoyancy and...
More Details - General Nautical Terminology Distance
The length of space between two points, often measured in nautical miles when referring to distances at sea.
In maritime contexts, "distance"...
More Details - General Nautical Terminology, Navigation Distance to Waypoint (DTW)
The measured distance, typically in nautical miles, between a vessel's current position and a predetermined navigational point or...
More Details - General Nautical Terminology, Navigation Dividers
A navigational tool consisting of two hinged legs with pointed ends, used by mariners to measure distances on a nautical chart.

Dividers...
More Details - Flag Semaphore, Signals & Communication Letter D (Flag Semaphore)

This shape represents the Letter D (Flag Semaphore) and the Number 4 (Flag Semaphore).
- Morse Code, Signals & Communication Letter D (Morse Code)
International Morse Code sequence representing the letter D.
- General Nautical Terminology DodgerScreen fitted to give the crew protection from wind and spray
- General Nautical Terminology, Weather (Meteorology) Dogger
Sea area of the Met Office Shipping Forecast. Spans Dogger Bank in the central North Sea, between the UK and continental Europe.
Named after...
More Details - General Nautical Terminology Dog Watch
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A shortened watch period aboard a vessel, typically divided into two shifts from 16:00 to 18:00 and 18:00 to 20:00, to allow for a rotation of... - General Nautical Terminology DolphinA mooring post or group of piles
- General Nautical Terminology, Navigation DOP
Used in satellite navigation and geolocation to provide the likely accuracy of a satellite-derived position.
The DOP concept is essential to...
More Details - General Nautical Terminology Double UpTo put out extra mooring lines when a storm is expected
- General Nautical Terminology DouseTo lower a sail; To extinguish a light quickly
- General Nautical Terminology, Weather (Meteorology) Dover
Sea area of the Met Office Shipping Forecast. Spans the English Channel at the Strait of Dover between England and France.
Named after the port...
More Details - General Nautical Terminology, Parts of a Boat Downhaul
A downhaul is a line or tackle to apply downward tension on a sail or spar to control its shape and optimise performance.
The downhaul is an...
More Details - General Nautical Terminology DownstreamThe direction towards which the stream flows
- General Nautical Terminology Downwind
Refers to the direction in which the wind is blowing relative to a specific point of reference.
When sailing or navigating on the water,...
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