- 行业: Earth science
- Number of terms: 93452
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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, ...
(1) A method for determining time or longitude by observing the passage (transit) of one or more circumpolar stars (time stars) through the vertical plane through Polaris. (2) The same as in the previous definition, but passage through the meridian is used instead. Also spelled Dellen's method and Doellen's method.
Industry:Earth science
One of six map projections devised by M. Eckert for mapping the entire sphere onto the plane in such a way that the poles are represented by straight lines half the length of the equator. Eckert's map projections are usually identified by Roman numerals from I to VI. Numbers I and II are map projections into the interior of a trapezoid; number I is an equidistant map projection; number II is an equal area map projection. Numbers III and IV represent meridians by elliptical arcs (number III is also known as Ortelius's map projection); number IV is an equal area map projection. Numbers V and VI represent meridians by sinusoidal arcs; number VI is an equal area map projection.
Industry:Earth science
The movement of a tidal current away from shore or down a tidal river or estuary.
Industry:Earth science
The condition resulting from the combination of eccentricity of circle and eccentricity of alidade. The effect of eccentricity of instrument on an observed direction is eliminated by having the verniers or micrometer microscopes with which the circle is read spaced at equal distances around the circle.
Industry:Earth science
The eastern intersection of the plane through the vertical and perpendicular to the astronomical meridian with the horizon.
Industry:Earth science
(1) That ground station which transmits SHORAN signals and about which an aircraft flies to maintain a circular path. The other ground station is then referred to as the rate station. The term is rarely used. (2) That navigation station, of a pair, from which a vessel doing a hydrographic survey tries to maintain a fixed distance. The second station of the pair is then called the rate station.
Industry:Earth science
The slow change of frequency of a source of periodic signals for example, the change in the frequency emitted by a crystal oscillator. The change may be caused by varying temperature, aging of the crystal or other components of the oscillator, etc. , none of which can be predicted or completely controlled.
Industry:Earth science
A non-linear error, in the readings from a compass, resulting from one or more of the following conditions: (a) a straight line through the ends of the magnetic needle fails to pass through the center of rotation of the needle; (b) the center of rotation of the needle does not coincide with the center of figure of the graduated circle; or (c) the line of sight fails to pass through the vertical axis of the instrument.
Industry:Earth science
