- المجال: 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, ...
Any datum in which the Earth's center of mass is involved in specifying the coordinate system. The center may be involved directly, e.g. by specifying that the origin of the coordinate system be at the center of mass. It may be involved indirectly, e.g., by including specifications for values of gravity or gravity potential. A geocentric datum is sometimes referred to as an absolute geodetic datum.
Industry:Earth science
A coordinate system with two intersecting, orthogonal axes one of which (the x-axis) lies in the galactic plane and the other (the z-axis) is perpendicular thereto. One coordinate (called galactic longitude) is the angle from the plane of the two axes to the plane containing the z-axis and the point in question; the second coordinate (called galactic latitude) is the complement of the angle from the z-axis to the line between the point in question and the point of intersection of the two axes. Two such systems have been in general use. The first, established by Ohlsson's conversion tables of 1932, placed the pole of the system at 12h 40m right ascension and +28<sup>o</sup> declination. The origin for galactic longitude was the ascending node of the intersection (the x-axis) of the galactic plane with the plane of the celestial equator. Coordinates in this system are labeled with a subscript I. In 1958, the International Astronomical Union adopted a system in which the galactic pole is at 12h 49m right ascension, +27. 4<sup>o</sup> declination, and the origin of galactic longitudes is at a position angle of 123<sup>o</sup> with respect to the pole of the equator. The equator and equinox of the old system are those of 1900. 0; those of the new system are of 1950. 0 (and are labeled with the subscript II). Galactic longitudes in the new system are approximately 32<sup>o</sup> greater that the longitudes in the old system.
Industry:Earth science
(1) In general, the bearing of a line. (2) In law, the direction of a line run with a compass or transit and referred to a meridian.
Industry:Earth science
Exaggeration of the ratios between densities of elements of an image.
Industry:Earth science
A flat, fan-shaped region at the mouth of a river and composed of sediment deposited by the river.
Industry:Earth science
The magnetic deviation of a compass after compensation or adjustment.
Industry:Earth science
In a conical map projection of normal aspect, the ratio of the angle Δθ between meridional lines on the graticule to the angle Δλ between corresponding meridians on the rotational ellipsoid.
Industry:Earth science
The angle between a ray from the exposure station through the principal point in the image plane of an oblique camera, and a ray to the boundary of a horizontal plane through the perspective center.
Industry:Earth science
(1) The technique of selecting and outlining, on pictorial sources of information or on a map manuscript, those features worthy of being included on a map. (2) A preliminary step in compiling a map.
Industry:Earth science
