- Отрасли: 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, ...
The point formed by lines connecting opposite corners of quarter sections in a section of land. It is also called the center quarter corner.
Industry:Earth science
A chronometer equipped with a device which automatically breaks an electric circuit to indicate a specific time or interval of time.
Industry:Earth science
Replacement of one device or instrument by another in such a way that if the original object was vertically over a mark, then so is the replacement. Some mountings are designed to hold a number of different kinds of instrument and targets, and are therefore made to allow forced centering. For example, a theodolite may be centered over the mark and, when observations are completed there, be replaced by a target which is then also automatically centered.
Industry:Earth science
A camera which takes a partial or complete panoramic photograph of the terrain. Some designs contain a lens system and slot like aperture which rotate about an axis perpendicular to the optical axis, the photographic film remaining fixed in position during the exposure. Other designs place a rotating prism in front of the lens system proper, the lens system itself remaining fixed. Still other designs rotate the entire camera, the photographic film being exposed as a sequence of frames. Only the first kind is used at present for taking aerial photographs.
Industry:Earth science
A method of determining details of the terrain, in a small topographic survey, by covering the region with a rectangular grid marked by stakes at 15, 20 or 30 meter intervals, determining the relative elevations at nodal points, and locating all irregularities or significant features from the closest pair of intersecting lines of the grid. Contours are drawn by interpolation.
Industry:Earth science
A bench mark the elevation of which with respect to mean sea level at a nearby tidal gage has been determined and which is used as reference for that tidal gage and for tidal datums. National geodetic organizations follow two different policies with respect to tidal bench marks. (a) The elevation of a tidal bench mark, once determined, is kept fixed. Changes in mean sea level at the tidal gage will then not affect elevations of points in the leveling network connected to that gage. (b) The elevation of the tidal bench mark is redetermined at intervals. Elevations of points in the leveling network then change with the location of mean sea level on the tidal gage, but mean sea level itself does not change. A tidal bench mark may be included in a geodetic line of levels.
Industry:Earth science
The art of expressing graphically, by maps, the known physical features of the Earth or of another celestial body. It usually includes showing the works of man and his varied activities. (2) The science, art and technology of making maps, together with the study of maps as scientific documents and works of art. (3) The theory and practice of making maps. (4) The process of making maps. The process is generally considered to include all steps from conception to finished product. The usual steps in the process are: (a) establishing the coordinate system for the map; (b) plotting the data onto the map from surveys or other sources (including other maps); (c) filling in where data are insufficient and generalizing where data are too plentiful; (d) comparing the resulting manuscript form of the map with new data (field checking) gathered specifically for this purpose; (e) making plates or other printing intermediates; and (f) printing copies of the map. In the context of the above definitions, the term may be regarded as including all types of maps, plans, charts, plots, and section; three-dimensional models and globes, etc. Although some authorities consider the term to include land surveying, hydrographic surveying, and photogrammetric surveying as part of cartography, this viewpoint is not common.
Industry:Earth science
A code (1) based on a pseudo - random sequence of numbers, i.e., based on a sequence (usually periodic) of numbers generated according to definite mathematical rules but having approximately the statistical properties of a random sequence of numbers. A common method of generating a pseudo - random sequence containing numbers x<sub>1</sub>, x<sub>2</sub>, . . . . . . . . x<sub>N</sub> uses the method of congruences: x<sub>n+1</sub> = ax<sub>n</sub> " b (mod T), where b and T are relatively prime integers. a and b are chosen to make the sequence as long as possible before it repeats, while keeping the numbers as random as possible. T is chosen to fit the base of the number system used by the computer. Pseudo random codes have been used in cryptography, in radio- communications systems, distance-measuring instruments operating at radio frequencies. The purpose of the first application is secrecy; that of the second two applications is lessening the effect of extraneous noise on the signals.
Industry:Earth science
