- 行业: Earth science
- Number of terms: 93452
- Number of blossaries: 0
- Company Profile:
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 chart showing the shape of the Earth's magnetic field by isogonic, isoclinic, or isodynamic lines.
Industry:Earth science
A lane cleared along a boundary line which passes through a wooded region. A boundary vista is used to make it easy to identify a boundary line and to help civil administration relating to the boundary line.
Industry:Earth science
A panel on a map, often with decoration, inclosing the title or other legends, the scale, etc.
Industry:Earth science
Facing the wind in the northern hemi-sphere, atmospheric pressure decreases toward the right and increases towards the left; the reverse is true in the southern hemisphere.
Industry:Earth science
That point, on the optical axis of an optical system, which is midway between the front and rear nodal points of the system. For a thin lens in air, the optical center, front and rear nodal points, and first and second principal points are all one and the same point. An oblique ray, even if it passes through the optical center, still undergoes a longitudinal displacement which increases with the thickness of the lens.
Industry:Earth science
An optical filter which allows only light within a certain narrow range of frequencies to pass through. Color filters have been used in the telescopes of both leveling instruments and of theodolites to improve the accuracy with which an object can be sighted. e.g., a Wratten #26 Stereo Red has been found best for use in leveling, a Wratten #8 K-2 orthochromatic has been found best for use in theodolites and transits.
Industry:Earth science
The relative change (expansion or contraction), expressed as a ratio, in a linear dimension of a body, corresponding to a change of 1<sup>o</sup> in the body's temperature. The coefficient of expansion, as it is generally called, may be in terms of the Celsius (SI), Fahrenheit, or other thermometric scale. To a very great extent, its magnitude is peculiar to the material' a steel tape, for example, has a coefficient of expansion about 25 times as great as has an invar tape. The coefficient is usually expressed as a decimal fraction. In a measure of length such as the length of a base line, it enters as a correction which is the product of the coefficient of expansion of the apparatus used, the length measured, and the difference between the temperature at which the measurement was made and the temperature (standard or calibration) at which the length of the apparatus is known.
Industry:Earth science
A statistical procedure for identifying those points in the data about which the data seem to cluster.
Industry:Earth science
A camera placed on a mountings which allow the optical axis to be kept pointed in the direction of a moving object such as an automobile, a missile or an artificial satellite. Small tracking cameras may be directed manually by the operator, who looks through an auxiliary optical system (guiding telescope) at the object being tracked. Larger tracking cameras are usually directed automatically by an optical system in which photocells take the place of an operator's eye, or by an auxiliary radar.
Industry:Earth science
A tripod similar to the Johnson tripod but simplified and made lighter. In the United States of America, it replaced the Johnson tripod about 1900.
Industry:Earth science
