- 行业: Earth science
- Number of terms: 93452
- Number of blossaries: 0
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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 unit of luminance equivalent to 1/π candela per square foot. Equivalently, the luminance of a perfectly flat, diffusing surface radiating one lumen per square foot.
Industry:Earth science
(1) The representation of a set of N points (pairs of numbers) by a smooth function, of a single variable, containing fewer than N defining constants. This is a special case of smoothing and curve fitting. (2) Representation of a set of N points in space by a smooth surface in that space, the surface being specified by too few constants to allow it to pass through all the points. A fit is also called a smoothing or an adjustment; the process is called fitting, curve fitting or adjustment. (3) An expression of how well a curve or surface represents a given set of numbers i.e., a word or number used to give an idea of how far the given points lie from the curve or surface representing them. E.g.., to say that a fit is good is to imply that the points lie acceptably close to their geometric representation; to say that the fit is poor is to imply the opposite. The root mean square value of the distances is frequently used to indicate fit.
Industry:Earth science
The negative of the coefficient of the second-degree, zonal harmonic in the expansion of the Earth's gravitational potential into spherical harmonics, normalized and adjusted to be dimensionless. Its non-normalized value is on the order of 10 <sup>-3</sup>
Industry:Earth science
The technique of making minor adjustments of detail on a map to maintain the proper relative positions of symbols.
Industry:Earth science
A source, natural or artificial, of events believed to occur at such uniform intervals of time that the frequency of the events can be used as a standard against which other frequencies or intervals of time can be compared. The Earth's rate of rotation with respect to the distant galaxies or fixed stars was at one time considered suitable as a frequency standard. The period of rotation was subdivided into smaller units by clocks. When the rate of rotation was found to be irregular, the rate of revolution of the Earth in 1900.0 was adopted. This standard was replaced in 1968 by the frequency of light emitted by the cesium atom in a specified transition between atomic energy levels. Frequency standards whose accuracy is highest are called primary standards; those of high precision but of lower accuracy are called secondary standards.
Industry:Earth science
The range of frequencies corresponding to those of normally audible tones. Audio frequencies generally range from 16 Hz to 30 kHz, but the range is often taken to be much less.
Industry:Earth science
A field in which the force at each point is caused by gravitation only.
Industry:Earth science
The process of rendering a developed, photographic image permanent by removing the unaffected, light sensitive material.
Industry:Earth science
(1) Land, along the course of a stream, which is subject to inundation during periods when the water's height exceeds the normal for being full to the banks. (2) Land which is parallel to the stream with approximately level ground, gentle longitudinal slope corresponding to the grad-ient of the stream, and very flat backslope. (3) Natural terrain frequently consisting of low lying, timbered land interspersed with swamp, marsh, small lakes, ponds and bayous.
Industry:Earth science
An optical filter which reduces the intensity of light reaching a light sensitive surface such as photographic film, without affecting the rendition of the color tones in the original scene.
Industry:Earth science
