English

(n.). An offshore hazard to surface NAVIGATION with substantially less clearance than the surrounding area and composed of unconsolidated material.

The narrow zone seaward from the low tide shoreline, permanently covered by water, over which the beach sands and gravels actively oscillate with chan­ging wave conditions.

The line where SHORE and water meet. Although the terminology of COASTS and SHORES is rather confused, shoreline and coastline are generally used as synonymous.

Shoreline maps are the graphic repre­sen­tation of planetable and photogrammetric surveys. The maps contain graphic data relating to the shoreli­ne, alongshore natural and man‑made features, and a narrow zone of natural and man‑made features inland from the shoreline. The original sources of a shoreli­ne map are ground survey data and photographs. Utilizing these sources, photogrammetric map compila­tion techniques, and instruments, cartographers generate shoreline maps, overlays, and associated data. The data are primarily generated to support nautical chart mainte­nance, new nautical chart construction, and hydrogra­phic survey operations.

An underwater acoustic position fixing system comprising a minimum of three hydrophones on the hull of a surface vessel. Three ranges are measured to a beacon either mounted on the seabed or a submersible to obtain a three-dimensional position fix.

PRECIPITATION, often short-lived and heavy, falling from convective CLOUDS; the drops or solid particles in showers are usually bigger than the corre­sponding elements in other types of PRECIPI­TATI­ON. Showers are characterized by their sudden begin­ning and ending, generally by large and rapid changes of intensity, and, most frequently, by the appearance of the sky; namely, rapid alternations of dark, mena­cing CLOUDS (cumulonimbus) and of CLEARANCES of short dura­tion.

An accumulation of spongy white ice lumps, a few centimetres across; the lumps are formed from grease ice or slush and sometimes from anchor ice rising to the surface.

A SHUTTER located between the lens elements of a CAMERA; usually consisting of thin metal leaves which open and close or revolve to make the EXPOSURE.