The structure or fitting will prevent the passage of water through the structure or fitting in any ordinary sea conditions.
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GROIN
A structure (usually one of a group) extending approximately perpendicular from a shore to protect the shore from erosion by tides currents, or waves or to trap sand for making a beach.
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MAGNETIC FILTER
A filter element that, in addition to its filter medium, has a magnet or magnets incorporated into its structure to attract and hold ferromagnetic particles.
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INDIRECT ECHO
A radar echo which is caused by the electromagnetic energy being transmitted to the target by an indirect path and returned as an echo along the same path. An indirect echo may appear on the radar display when the main lobe of the radar beam is reflected off part of the structure of the ship (the stack for example) from which it is reflected to the target. Returning to own ship by the same indirect path, the echo appears on the PPI at the bearing of the reflecting surface. Assuming that the additional distance by the indirect path is negligible, the indirect echo appears on the PPI at the same range as the direct echo received. Also called FALSE ECHO.
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FAIRWATER
A structure that improves the streamlining of a vessel.
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DOLPHIN
The structure consisting of a number of piles driven into the seabed or riverbed as a marker.
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INSTRUMENT SHELTER
A cage or screen in which a thermometer and sometimes other instrument are placed to shield them from the direct rays of the sun and from other conditions that would interfere with registration of true conditions. It is usually a small wooden structure with louvered sides.
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DAY BEACON
An unlighted fixed structure which is equipped with a dayboard for daytime identification.
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LIGHTHOUSE
A distinctive structure exhibiting a major navigation light.
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AID TO NAVIGATION
A device or structure external to a craft, designed to assist in determination of position, to define a safe course, or to warn of dangers or obstructions. If the information is transmitted by light waves, the device is called a visual aid to navigation; if by sound waves, an audible aid to navigation; if by radio waves; a radio aid to navigation. Any aid to navigation using electronic equipment, whether or not radio waves are involved, may be called an elec- tronic aid to navigation. Compare with NAVIGATIONAL AID, meaning an instrument, device, chart, method, etc., intended to assist in the navigation of a craft.
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DOCK
A structure built along, or at an angle from, a navigable waterway so that vessels may lie alongside to receive or discharge cargo. Sometimes, the whole wharf is informally called a dock.
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