- 行业: Earth science
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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, ...
That eccentricity of an ellipsoid which is the eccentricity of a section by a plane through the longest and shortest axes.
Industry:Earth science
The retarding force exerted by an atmosphere on a body moving through it. For atmospheres similar to the Earth's, the formula is the same as that given in the definition of air drag. However, atmospheres like those of Jupiter, Venus or the Sun may induce other forces which may have greater effects on bodies moving through them.
Industry:Earth science
A datum defined for use with the TRANSIT system of navigational satellites (also called the Navy Navigation Satellite System).
Industry:Earth science
That eccentricity of an ellipsoid which is the eccentricity of an equatorial section of the ellipsoid.
Industry:Earth science
The world we inhabit; the third planet from the Sun in the Solar System. Also referred to, in literature, as the terrestrial sphere. It is an approximately spherical body revolving around the Sun in a period of one year at a distance of approximately 150 000 000 km. It rotates at the rate of one complete rotation per day, although the length of the day in atomic seconds varies irregularly and in any event depends on how the axis of rotation is defined. It has one satellite, the Moon; this has mass about 1/81 that of the Earth and is at an average distance of about 384 000 km. The characteristics most important to geodesy are given in the Appendix.
Industry:Earth science
The right to use the land at a designated distance below the surface of the land e.g., for pipelines, electric and telephone circuits and cables, storage facilities, etc.
Industry:Earth science
A rotational ellipsoid of given dimensions and rate of rotation, containing a given mass and on which the gravity potential has a given value.
Industry:Earth science
The hypothesis that the continents of today were at one time integral parts of a single large continent (Pangea) or of a northern continent (Laurasia) separated by the Tethys Sea from a southern continent (Gondwanaland). These integral parts then separated and drifted to their present locations. The original idea is traceable to Antonio Snider (1858); scientific evidence for the hypothesis was provided by Suess (1900), Taylor (1910), and, very substantially, by Wegener (1929) and du Toit (1937). However, the evidence was not considered strong enough for general acceptance until paleomagnetic data on sea floor spreading and movement of the magnetic pole were produced in the late 1960's. Discovery of paleomagnetic variations showed that the motion of the magnetic pole, as determined from measurements on rocks in one continent, did not correspond to the motion as determined by similar measurements in another continent. The theory of continental drift was further strengthened by the discovery that the floor of the oceans had apparently been spread apart by material coming up from the mantle through the mid oceanic ridges. The theories of continental drift and plate motions (plate tectonics) are almost identical. The principal difference has been that the former considers the continents themselves as moving, isolated blocks. The latter considers the continents move as integral parts of larger blocks (plates) that are contiguous and move as wholes. The difference has diminished in recent years with the introduction, into the theory of plate motion, of the hypothesis that some or all of the blocks are separated by regions of plastic material which does not move with the blocks.
Industry:Earth science
(1) The eccentricity (1) of an elliptical orbit. (2) The eccentricity (1) of the osculating ellipse or average ellipse of an orbit.
Industry:Earth science
