- 行业: 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, ...
A hedge, structure, or partition erected to enclose a piece of land or to divide a piece of land into district portions or to separate two continuous estates.
Industry:Earth science
(1) Photographic film sensitive to infrared radiation. (2) In particular, photographic film sensitive to radiation in the near-infrared part of the spectrum.
Industry:Earth science
The flattening of a rotational ellipsoid representing an Earth in hydrostatic equilibrium.
Industry:Earth science
Lines, in a spectrum, formed by interference between waves of electromagnetic radiation. Fringes are usually observed as faint lines on each side of the strong central line produced by light received directly, without interference. Fringes of light can be observed as a series of parallel light and dark lines. If the light is not monochromatic, the fringes have colored edges. The distance between two neighboring fringes depends on the difference in phase of the interfering waves and can be used to determine the difference in distance traveled by the two waves. The Väisälä base line apparatus depends for its accuracy on the counting of fringes. The same principle is used in radio interferometry.
Industry:Earth science
The path along which electromagnetic radiation travels between any two points will be that for which the time taken for the journey is an extremum. The time need not be a minimum; it can be a maximum.
Industry:Earth science
The line of a fence around a tract, maintained for at least 30 (probably 50) years, which must be taken as fixing the correct boundaries of the tract as against a later survey.
Industry:Earth science
A lens having a saw-toothed cross section in the radial direction; one side of each tooth is straight and vertical; the other side slants and has the curvature of the corresponding zone of a convex (convergent) lens. A Fresnel lens has the same optical properties as a regular lens of the same diameter and focal length but is very much lighter because the lens does not increase in thickness from edge to center as does a regular convex or plano-convex lens. Fresnel lenses are therefore used in situations calling for a very large lens of reasonable weight and not requiring the ultimate in faithfulness of the image e.g., as collimating lenses for the lamps in lighthouses. However, they have also been used in cameras, photographic projectors, and telescopes.
Industry:Earth science
The location of that plane which is perpendicular to the principal axis of an optical system and onto which a stellar image is focused. In an ideal optical system, the sidereal focus is called the principal focal plane. A camera or telescope is said to be in sidereal focus when rays incident from a great distance come to a focus in the plane of the photographic plate or of the reticle. The sidereal focus is sometimes called the solar focus.
Industry:Earth science
