- Отрасли: Earth science
- Number of terms: 93452
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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, ...
In describing a traverse, the azimuth and length of a single line of traverse considered together.
Industry:Earth science
A line, on a map, along which there is no variation from the exact scale of the map. There are two isoperimetric curves passing through every point on a map drawn using an equal area map projection. This characteristic gives that class of map projections some preference for maps used in engineering.
Industry:Earth science
The period T<sub>d</sub>, in sidereal hours, at a point at geodetic latitude φ, as given by the formula.
Industry:Earth science
The interval of time between two successive upper or lower transits of the Sun across a given meridian. Because the revolution of the Earth is not uniform, apparent solar days vary in length throughout the year. The greatest deviation from a mean solar day is not quite a half minute in either direction.
Industry:Earth science
A coordinate system the axes of which are fixed with respect to the Earth. Because the Earth not rigid but (a) is imperfectly elastic and (b) moving irregularly in all its parts, the above definition is inadequate for specifying a unique, time-invariant system. A valid definition would be, for example, a coordinate system the axes of which are parallel to those of another coordinate system defined as follows: (a) a rectangular Cartesian coordinate system in three-space, with the three axes fixed with respect to each other, is defined; (b) two of the axes lie in a plane passing through three given points in the Earth (one of these points is usually the Earth's center of mass), and one of these axes passes through two of the points; (c) the direction of the third axis with respect to the plane is specified; (d) a (possibly curvilinear), time invariant coordinate system is specified by a transformation from the Cartesian coordinate system to this second one; and (e) the Earth-fixed coordinate system is then defined by parallelism with respect to the second coordinate system. However, the fact that all parts of the Earth are probably in motion with respect to each other makes it unlikely that one Earth-fixed coordinate system, however precisely defined, will serve all needs. Passing through two given points in the Earth (one of these points is usually taken as the Earth's center of mass).
Industry:Earth science
A Cartesian coordinate system in the plane, the axes intersecting at right angles.
Industry:Earth science
A base-line apparatus composed of bars whose lengths were defined by the distances between their end faces or points. In use, the bars were laid end to end. One bar was kept in position while another bar was moved ahead.
Industry:Earth science
One of a set of coordinates in an oblique Cartesian coordinate system.
Industry:Earth science
(1) One of a set of coordinates in the neighborhood of a point at which the gradient of the metric tensor is zero. (2) One of a pair of parameters (u,v), on a surface, such that the curves v = constant are a singly infinite family of geodesics on that surface and the curves u = constant are the family of curves orthogonal to the geodesics.
Industry:Earth science
(1) The difference of elevation represented by adjacent contour lines. (2) The difference of elevation between two adjacent contours.
Industry:Earth science
