- Branche: 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, ...
The quantity a/(1 - e² sin²φ)½, where a is the length of the semi major axis of a rotational ellipsoid, e is the eccentricity and φ is the geodetic latitude. It is often denoted by N or v. Geometrically, it is the distance, along the normal at latitude φ, from the ellipsoid to the minor axis.
Industry:Earth science
The depth, in meters, at which paired, protected and unprotected thermometers attached to a Nansen bottle are reversed. The difference between the corrected readings of the two thermometers represents the effect of the hydrostatic pressure at the depth of reversal. This depth may been be determined by formula or from a graph of depth anomaly.
Industry:Earth science
A depth, below the water's surface, at which properties of the water should be measured and reported, according to a proposal by the International Association of Physical oceanography in 1936. The proposed standard depths, in meters, are: 0, 10, 20, 30, 50, 75, 100, 150, 200, 300, 400, 500, 600, 1000, 1200, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000.
Industry:Earth science
(1) A correction applied to the average of a series of observations on a star or planet, to take account of the divergence of the apparent path of the star or planet from a straight line. Any star which is not an equatorial star does not strictly run along the horizontal wire of a transit instrument as it crosses the meridian of the observer. This phenomenon was first observed by Cassini and was explained by him in 1719. Observations on a star for the purpose of calibrating a micrometer are subject to correction for the apparent curvature of the star's path during observation, as also are some observations for azimuth. The correction to reduce an observation for latitude on a star close to but not on the meridian to what it would be if the star were on the meridian may be considered a curvature correction. (2) The correction applied to some geodetic data to take into account the divergence of the surface of the Earth (or its representing ellipsoid) from a plane. In geodetic leveling, the curvature correction and the effect of atmospheric refraction are considered together, and tables have been prepared from which combined corrections can be taken. In aerotriangulation, the curvature correction is also usually combined with the correction for refraction.
Industry:Earth science
A line, on the surface of the geoid, which is at a constant height above the rotational ellipsoid used as reference. Geoidal contours represent differences in height between the geoid and the ellipsoid of reference. They depend not only on the shape of the geoid but also on the dimensions and location of the ellipsoid to which the heights are referred. The same geoid referred to different ellipsoids will give different sets of geoidal contours. Although the definition specifies a rotational ellipsoid (spheroid), it will remain valid if the word rotational is dropped.
Industry:Earth science
The largest amount, theoretically, by which a star's apparent direction varies, as seen from a fixed latitude, during one day solely because of the Earth's rotation. It is commonly denoted by k and is given by the formula k = (2πR cos φ')/cT , in which R is the radius of the Earth at the observer's geocentric latitude φ', T is the length of the sidereal day and c is the speed of light.
Industry:Earth science
The process of subjecting an exposed, light sensitive surface to chemical agents in order to make visible the latent image formed by the action of light during exposure.
Industry:Earth science
That portion of the Earth extending from the lower boundary of the mantle to the center of the Earth. The radius of the core is about 3500 km; the core's surface is about 2800 km below the Earth's surface. Only longitudinal (P) seismic waves will propagate through the core; trans-verse (S) seismic waves will not. Because liquids will transmit longitudinal but not transverse seismic waves, the core (or at least that part adjoining the mantle) is thought to be liquid. There is some seismological evidence that a region from the center of the Earth out to about 1400 km is partly or entirely solid. This portion is called the inner core; the other, liquid portion is then called the outer core.
Industry:Earth science
The corrections ΔD <sub>i</sub> and ΔL <sub>i</sub> to the x component D <sub>i</sub> and the y component L <sub>i</sub>, respectively, of course i (of length l <sub>i</sub>) are given by <br.
Industry:Earth science
