- 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 piece of wood or metal having a triangular cross section and marked, along each face adjacent to an edge, at regular intervals; the marks are numbered so as to indicate the ratio between lengths along the edge and lengths or distances along an object. An engineer's scale therefore provides six different graphic scales, two along each edge on opposing faces.
Industry:Earth science
An issue of a previously published map, chart, or atlas differing from previous issues in its factual content, layout, or design.
Industry:Earth science
The situation that arises when a single point on a route alinement has two values because of joining preliminary and final stationing. Thus, station 123+45. 6 ahead equals 123+54. 3 back.
Industry:Earth science
That part of engineering which deals with the design of devices, machines, and structures in such a way as to make them best fitted to use by humans.
Industry:Earth science
The value HsN calculated for the elevation of a point PN by dividing a theoretical value WN of the potential function at PN (assuming the value to be 0 on the geoid) by a theoretical, average value gsN of gravity acceleration between PN and the geoid. The theoretical value τn of gravity acceleration is calculated from a standard gravity formula τ<sub>n</sub> = τ<sub>o</sub> (1+ (β/2) cos 2φ<sub>n</sub> - 2Hn/R) instead of from measured values. β<sub>n</sub> is the value of acceleration at latitude φ<sub>n</sub> and elevation Hn; τ<sub>o</sub> and β are constants and R is an appropriate radius of the Earth.
Industry:Earth science
(1) The angular distance of a celestial body from the Sun, as viewed from the Earth. An elongation of 0<sup>o</sup> is called conjunction, one of 180<sup>o</sup> is called opposition and one of 90<sup>o</sup> is called quadrature. (2) The geocentric angle between a planet and the Sun, measured in the plane of the planet, Earth and Sun. Elongation is measured from 0<sup>o</sup> to 180<sup>o</sup> east or west of the Sun. (3) The geocentric angle between a planetary satellite and its primary, measured in the plane of the satellite, planet, and Earth. Elongation is measured from 0<sup>o</sup> east or west of the planet. (4) That point, in the apparent daily motion of a star about the celestial pole, at which the star's rate of change of azimuth becomes zero; the point at which the star is seen to cease increasing its bearing east or west of the celestial pole and to reverse its direction of motion eastward or westward. An equivalent definition is, that point at which the parallactic angle of star and observer is 90<sup>o</sup>.
Industry:Earth science
The passage of a celestial body or point across the ephemeris meridian.
Industry:Earth science
An elevation arrived at in the office after the index, level, rod and temperature corrections have been applied to the observed differences of elevation and new elevations have been calculated.
Industry:Earth science
The equation expressing the rate of change of pressure p with geometric height (or depth) h as a function of density ρ and gravity acceleration g, when all Coriolis forces, friction and vertical accelerations, and the curvature of the Earth are considered to have negligible effects. The equation is usually written p/dh = -rg.
Industry:Earth science
