- Branche: 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 device using the monochromatic emission from a narrow band in the spectrum of a suitable molecule (e.g., ammonia or methane) or atom to control the frequency of a circuit resonant at the frequency of radio waves. The principal geodetic application has been to the generation of precise frequencies for clocks. The earliest masers used in this way depended on ammonia for controlling the frequency. At present, the most accurate control is obtained by using masers depending on rubidium, cesium or hydrogen gas.
Industry:Earth science
(1) A unit of length defined by international agreement to have a length of 1 metre (1 meter). In particular, when written International Metre. (2) The unit of length defined by the International Prototype Metre (Meter). The term is best not used with this meaning because the meters defined in 1960 and 1983 are also international meters.
Industry:Earth science
The change in longitude, along a celestial position line, per 1' change in latitude.
Industry:Earth science
(1) An azimuthal map-projection mapping a hemisphere onto a plane by projecting from a point on the sphere onto the plane tangent to the sphere at the opposite end of the diameter through the center of projection. It is given by the formulas<br>
Industry:Earth science
A vector characteristic of a body moving in a straight line and equal in magnitude to the product of the mass by the velocity. Also referred to as momentum when linear momentum is clearly meant. If the body is moving along a curve or otherwise rotating while moving, linear momentum should be used for the product of mass by instantaneous velocity and total momentum for the sum of the linear and angular momenta.
Industry:Earth science
Any machine, mechanical or electrical, that carries out mathematical calculations according to a predetermined set of algorithms. Also commonly called a computer when such use is not likely to be ambiguous.
Industry:Earth science
The arc at the celestial equator, or the angle at the celestial pole, between the upper branch of the local celestial meridian and the hour angle of the object of interest, measured eastward or westward from the local celestial meridian through 180<sup>o</sup> and labeled to indicate the direction in which the angle is taken.
Industry:Earth science
(1) A transverse wave propagated along the boundary between two elastic layers, both of which have elasticity. (2) A seismic wave on the Earth's surface, in which the particles vibrate transversely in a horizontal plane.
Industry:Earth science
