COAST & GEODETIC SURVEY, NATIONAL OCEAN SURVEY, U.S. Numerous bench marks of predecessor organizations to NOS, or parts of other organizations absorbed into NOS, still bear the inscriptions: U.S. Bench mark disks of either type may, on occasion, serve simultaneously to reference both tidal and geodetic datums. Bench mark disks may also be horizontal control points and are so designated on their stampings. Most geodetic bench mark disks contain the inscription VERTICAL CONTROL MARK NATIONAL GEODETIC SURVEY with other individual identifying information. A vertical geodetic bench mark identifies a surveyed point in the National Geodetic Vertical Network. The standard tidal bench mark of the National Ocean Service is a brass, bronze, or aluminum alloy disk 3-½ inches in diameter containing the inscription NATIONAL OCEAN SERVICE together with other individual identifying information. A primary bench mark is the principal (or only) mark of a group of tidal bench marks to which the tide gauge measurements and tidal datums are referred. A tidal bench mark is one near a tide station to which a tide staff and tidal datums are referred. (Ellis 1978) bench mark (BM)Ī fixed physical object or mark used as reference for a vertical datum. Some beaches have no berms, others have one or several. Nearly horizontal portion of the beach or backshore formed by the deposit of materials by wave action. A beach includes foreshore and backshore. Zone of unconsolidated material that extends landward from the low water line to the place where there is marked changes in material or physiographic form, or to the line of permanent vegetation (usually the effective limit of storm waves). Science of measuring water depths (usually in the ocean) in order to determine bottom topography. AĬombination of the low-water line and closing lines across the mouths of inland water bodies. The line from which maritime zones are measured. (Ellis 1978) bankĮdge of a cut or fill the margin of the watercourse an elevation of the seafloor located on a continental shelf or an island shelf and over which the depth of water is relatively shallow but sufficient for safe surface navigation (reefs or shoals, dangerous to surface navigation may arise above the general depths of a bank). That part of the beach that is usually dry, being reached only by the highest tides, and by extension, a narrow strip of relatively flat coast bordering the sea. Neither of these changes works a change in the riparian boundary. The loss of lands bordering on the seashore by sudden or violent action of the elements, perceptible while in progress a sudden and rapid change in the course and channel of a boundary river. This line represents the intersection of the appropriate datum on the outer limits of vegetation and appears to the navigator as the shoreline. Line drawn on a map or chart in lieu of a mean high water line (MHWL) or the mean water level line (MWLL) in areas where either may be obscured by marsh, mangrove, cypress, or other type of marine vegetation. Accuracy relates to the quality of a result and is distinguished from precision which relates to the quality of the operation by which the result is obtained. (Shalowitz 1964) accuracyĭegree of conformity with a standard. Accretion is the act, while alluvion is the deposit itself. This may be the result from a deposit of alluvion upon the shore, or by a recession of the water from the shore. The gradual and imperceptible accumulation of land by natural causes, as out of the sea or a river. Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.A-C| D-F | G-I | J-M | N-P | R-T | U-W A accretion.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.
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