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We believe every day’s a school day on a boat! That’s why we built Nautical Know-How, dedicated to answering your questions. Even better, if it can’t answer your question immediately, you can request it, and we’ll add it to our knowledge base.
Marine navigation has its own secret language, and let’s face it—half of it sounds like someone making things up after too much grog. You’ve got your ‘dead reckoning,’ which isn’t nearly as ominous as it sounds, and ‘bearing,’ which has nothing to do with polar bears but everything to do with pointing the right way. Don’t even get us started on ‘knots’—why measure speed like you’re tying a shoelace? And then there’s ‘fix (not for your engine) and ‘DR’ (spoiler: it’s not a doctor). If you’re baffled, don’t worry—we’re here to help you decipher this nautical code so you can sound like a pro, not a landlubber who’s lost their compass.
To move under the influence of wind, waves or water flow rather than a deliberately maintained track. A vessel can drift when stopped, disabled or intentionally allowed to move with the water, while a floating object drifts according to its windage and immersion. An anchored vessel that moves because the anchor is not holding is…
An official or purpose-produced representation of navigable waters and adjoining areas for marine navigation. A nautical chart can show depths, drying heights, coastline, dangers, aids to navigation, routes, limits, seabed information and notes relevant to passage planning. Scale, projection, horizontal datum, vertical datum and the edition or update status determine how its information must be…
A work surface arranged for consulting, marking and storing nautical charts and navigation records. It is usually part of a navigation station and may include chart drawers, instrument stowage, task lighting, electrical panels, radios or electronic displays. On smaller craft it may be compact, fold away or share another surface rather than accept a fully…
The vertical distance from chart datum to the seabed or the top of a charted underwater feature. Soundings printed on a nautical chart are referenced to chart datum. Adding the predicted or observed height of tide gives an estimate of the water depth at that time. The navigator then compares the result with the vessel’s…
An electronic navigation device that displays a vessel’s position on a digital nautical chart. A chart plotter combines position information, normally received from GNSS such as GPS, with an electronic chart. It can display course and speed, create waypoints and routes, and monitor progress during a passage. Depending on the installation, it may also show…
A highly accurate timekeeper used in traditional celestial navigation to determine longitude. A marine chronometer keeps the time at a known reference meridian while observations establish local time aboard the vessel. The difference between those times can be converted into longitude because the Earth rotates through 15 degrees in one hour. Traditional marine chronometers were…
Free from an identified obstruction, hazard or vessel. The word is used in instructions and reports such as “clear of the buoy,” “clear of the shoal” or “the stern is clear.” It describes separation from the particular object or danger being discussed, not a general guarantee that the surrounding water is safe. A vessel may…
The available distance between a vessel and an overhead, underwater or nearby obstruction. Vertical or overhead clearance is compared with the vessel’s air draught when passing beneath a bridge, cable or other structure. Under-keel clearance is the distance remaining between the vessel’s lowest point and the seabed or a submerged obstruction. The unqualified word “clearance”…
A point of sail on which a vessel sails as close to the wind as it can while keeping the sails drawing effectively. The sails are trimmed in and the vessel makes progress to windward on one tack. The closest useful angle varies with rig, sail condition, hull and appendages, wind strength, sea state and…
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...
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