- Branche: 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, ...
Any device or apparatus producing an image of an object. The term is used to include devices or apparatus not photographic in nature but which create images from radiation at wavelengths longer or shorter than those of light. It also includes apparatus producing sonic images. In most cases, however, the final product of an imaging system is a visual or photographic image.
Industry:Earth science
That part of the atmosphere containing a sufficient number of ions and electrons to cause appreciable dispersion of radio waves of frequency less than 1 GHz. The lower boundary of the ionosphere is at about 50 km (the upper boundary of the stratosphere) and the upper boundary (to the extent that one can be defined) is at about 2000 km. Four layers can be distinguished in the iono-sphere. The lowest, the D-layer, has an electron density of about 1000 electrons per cc at maximum; it appears only during the day and disappears at night. The maximum occurs at about 80 km. The E-layer extends from about 85 km to 140 km, contains about 100 000 electrons per cc at periods of least solar activity and about 150 000 electrons per cc at times of greatest solar activity. The F-layer extends from about 140 km outwards. The structure of the F-layer is extremely complex (electron density varies from about 500 000 to over 2 000 000 particles per cc). Two regions can easily be distinguished: the F1 region extends from about 140 km to about 200 km; the F2 region extends from 200 km on out. The ionization is caused principally by solar radiation. The D-layer appears to be caused by hard x-rays, the E-layer by soft x-rays, and the F-region by ultraviolet radiation and light.
Industry:Earth science
If the rays from each point on the object diverge in image space, a virtual image is formed of each such point at the intersection of the asymptotes to these diverging rays, and the virtual image of the object is the collection of the virtual images of the individual points.
Industry:Earth science
A method of solving the problem of determining, in a plane, the coordinates of a point A, given the coordinates of three points B, C, D and the measured angles BAC and CAD. The angles that CD and CB make with the x-axis are calculated first, from which the angles CDA and CBA are calculated. The distances CD and CB are next calculated and the coordinates of A then follow easily.
Industry:Earth science
A survey made to collect and correlate engineering data of a particular type or types over a given region. An inventory survey may be recorded on a map.
Industry:Earth science
(1) The narrative part of the new-status records. (2) A summary of and index to all essential actions that affect or have affected the title to or use of lands and resources, public domain.
Industry:Earth science
A surface of reference below mean sea level by half the range between mean lower low water and mean higher high water multiplied by 1.5
Industry:Earth science
Records of the occurrence of ice. Ice records of importance to engineers are usually obtainable from the following sources: reports by local engineers; statements by local residents; examination of structures damaged by ice; photographs of icy conditions; records of the U.S. Weather Bureau; records of the U.S. Geological Survey of flow of streams.
Industry:Earth science
A chain of islands describing a segment of an arc, generally convex outward from the continental region, and part of the major, global, active orogenic belt.
Industry:Earth science
Distortion of an image. Among the possible causes are distortion by the lens system, differential shrinkage of the film or paper, and motion of the camera while the picture was being taken.
Industry:Earth science
