- Industry: Earth science
- Number of terms: 93452
- Number of blossaries: 0
- Company Profile:
Founded in 1941, the American Congress on Surveying and Mapping (ACSM) is an international association representing the interests of professionals in surveying, mapping and communicating spatial data relating to the Earth's surface. Today, ACSM's members include more than 7,000 surveyors, ...
(1) The route along which a river or stream flows. (2) The river or stream itself.
Industry:Earth science
The amplitude or epoch of a harmonic constituent of the tide or tidal current at a place.
Industry:Earth science
(1) A unit of measure of solid angle corresponding to the area, on a sphere of unit radius, of a quadrangle composed of great arcs 1<sup>o</sup>. on a side. There are 129 600/π (approximately 41 250. 87) square degrees on a sphere, and approximately 3 282. 64 square degrees in a steradian. (2) A unit of area equal to 1/64 800 of the surface of a unit sphere. This definition and the preceding one do not define the same quantity. A solid angle (figure) having a solid angle (measure) of 1 square degree is not necessarily square. The quadrangle used in the first definition is not rectangular - the internal angles are slightly greater than 90<sup>o</sup> and the sides bow out.
Industry:Earth science
(1) One of a set of three coordinates (u, Ψ, λ) of a point in a spheroidal coordinate system of given distance 2k between foci of the rotational ellipsoids of the system. Spheroidal coordinates are related to the rectangular Cartesian coordinates (x, y, z) in a system whose axes coincide with those of the spheroidal coordinate system, by the equations x = (√(u² +k²)) cos Ψ cos λ , y = (√(u² +k²)) cos Ψ sinλ and z = u sin Ψ , in which u is the length of the semi major axis of the rotational ellipsoid through the point, Ψ is the reduced latitude of the point with respect to the same ellipsoid and λ is the angle from a reference plane through the minor axis to the plane through the minor axis and the point. Called an elliptic coordinate or ellipsoidal coordinate by some geodesists. Other version of the above set of coordinates and of the transformation equations are in use. e.g., the form x = rcosh Γ cos Ψ cosλ, y = rcosh Γ cos Ψ sinλ and z = rsinh Γ sin Ψ has been used in satellite geodesy. (2) A coordinate in a coordinate system on a rotational ellipsoid (spheroid). (3) A coordinate in a coordinate on a surface which is approximately spherical.
Industry:Earth science
An oceanic tide which fails to reach its predicted height at high water.
Industry:Earth science
A body of material that is impermeable or has only low permeability and occurs below the surface of the ground in such a position that it impedes horizontal movement of ground water and consequently causes a pronounced difference in the level of the water-table on opposite sides of it.
Industry:Earth science
(1) A surface, usually flat, to which elevations in the region being studied are referred. The surface is usually taken as nearly horizontal as possible. (2) The plane, corresponding to the surface in the first definition, in a stereoscopic model or photogrammetric instrument, to which heights or elevations are referred. Sometimes referred to simply as model datum or datum.
Industry:Earth science
The apparent locations of the planets relative to each other and to other bodies of the Solar system, as seen from the Earth.
Industry:Earth science
A particular, hypothetical line on the Earth separating neighboring regions in which the civil dates differ by one day. There is no international date line which has been formally adopted by the various nations of the world. In 1884, the International Meridian Conference, held in Washington, D. C. , established the meridian of Greenwich as the meridian from which time was to be reckoned. The meridian 180<sup>o</sup> from the Greenwich meridian thus became the international date line. The international date line in use by the U. S. Hydrographic Office is defined as follows: it is drawn from the North Pole due south along the 180th meridian to 75<sup>o</sup> N. ; thence southeastward, to the east of Herald Island, to 68<sup>o</sup> N and the longitude of the meridian passing between the Diomede Islands (approximately 168<sup>o</sup> 58' 22" W. ); thence due south through the Bering Straits to 65<sup>o</sup> 30' N. ; thence southwestward to 53<sup>o</sup> N. , 170<sup>o</sup> E. ; thence southeastward to 48<sup>o</sup> N. and the 180th meridian; thence due south to 5<sup>o</sup> S. ; thence southeastward to 15<sup>o</sup> 00' S. , 172<sup>o</sup> 30' W. ; thence due south to 45<sup>o</sup> 00' S. , 172<sup>o</sup> 30' W. ; thence southwestward to 51<sup>o</sup> S. and the 180th meridian; thence south to the South Pole.
Industry:Earth science
(1) A ground control point established by a subsidiary survey (not a survey for establishing geodetic control), placed at or near an important cultural feature or other feature to be included in the final map, and identifiable on the photograph. The number of detail points selected will vary with the nature of the terrain and the amount of detail needed on the map. Ten detail points per photograph are usually sufficient. (2) A selected, identifiable point used, particularly in oblique photographs, to assist in correctly locating features displaced because of elevation.
Industry:Earth science
