- 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, ...
A horizontal passage driven from a shaft to a vein across the course of the vein in order to reach the zone of the vein.
Industry:Earth science
(1) Determining the extent to which one randomly varying quantity can be expressed as a function of another or both can be expressed as functions of a third, non random quantity. This definition is extended to situations involving several variables by applying it to each different pair of variables in the set. Correlation is linear, quadratic, etc. , if the function is linear, quadratic, etc. The extent is measured by a quantity called the correlation constant or correlation coefficient. (2) The removal of discrepancies that may exist among survey data so that all data agree without apparent error. The terms coordination and correlation are usually applied to the harmonizing of surveys of adjacent regions or of different surveys over the same region. Two or more such surveys are coordinated when they are computed on the same datum; they are correlated when they are adjusted together.
Industry:Earth science
A curve showing the relationship between exposure and resulting density in a photograph, usually plotted as the density (D) against the logarithm of the exposure (log E) in candle meter seconds. It is also called a D-logE curve, Hurter and Driffield curve, H and D curve, sensitometric curve, time-gamma curve and density-exposure curve.
Industry:Earth science
That part of a current, disturbed from steady motion in equilibrium, which has the characteristic features of purely inertial movement.
Industry:Earth science
A line having a specific direction. Many variations of this basic definition are in use in different disciplines.
Industry:Earth science
A coordinate system consisting of a plane of reference called the equatorial plane, a plane of reference (called the zero meridian plane) perpendicular to the equatorial plane, and a point (called the center) on the line of intersection of the two planes. The coordinates of a point are (a) its distance from the center, (b) the angle at the center between the equatorial plane and a line joining the center to the point in question and (c) the angle from the zero-meridian plane to the plane which contains the center, the point in question and a perpendicular to the equatorial plane at the center.
Industry:Earth science
A contact screen composed of dots of magenta hue and variable density. It is used for making halftone photographic-negatives.
Industry:Earth science
The quantity gc obtained by subtracting from a gravity anomaly Δg the following gravity corrections: (a) the condensation gravity correction &3948;g <sub>c</sub>; (b) the free air gravity correction δg <sub>f</sub>; and (c) a Bouguer gravity correction δg <sub>B</sub>, a modified Bouguer gravity correction δg <sub>Bm</sub> or an expanded Bouguer gravity correction δg <sub>BE</sub>. Applying the condensation gravity correction is the mathematical analog of replacing all the mass between the reference surface and an equipotential surface through the point P at which gravity was measured by a thin layer of mass condensed onto the reference surface (or at a predetermined distance below it). Applying the free air gravity correction then changes gravity from its value on the reference surface to the corresponding value at elevation Hp, and applying the Bouguer gravity correction replaces the missing mass by the Bouguer plate or some modification thereof. If the distance (called the depth of condensation) of the layer of condensed matter below the reference surface is zero, i.e., if the mass is applied as a coating to the reference surface, the gravity anomaly is sometimes referred to as Faye's gravity anomaly, because Faye proposed putting the layer on the reference surface. However, because the term Faye's gravity anomaly has also been used for other kinds of gravity anomaly, the term is best not used at all. Note that to some extent, depending on how the mass to be condensed is estimated and on what kind of Bouguer correction is applied, the condensation gravity is a variant of the Bouguer gravity anomaly with topographic correction.
Industry:Earth science
(1) A geodetic datum which specifies that the center of the ellipsoid shall be located at the Earth's center of mass. It is customary to specify also that the shortest axis of the ellipsoid be parallel to the Earth's axis of rotation (instantaneous, average or conventional) or to some other similar line of known orientation. Another axis may be required to be parallel to plane of the Greenwich meridian or, for some purposes, to the plane of the zero meridian of the Bureau International de l'Heure. More often, the ellipsoid is placed to provide a satisfactory fit to the geoid. A rectangular coordinate system is often associated with a geocentric geodetic datum by placing the origin of that coordinate system at the center of the ellipsoid, making the x- and z-axes coincide with the longest and shortest axes, respectively, of the ellipsoid, and requiring that the coordinate system be right handed. (2) A geodetic datum specifying that the center of the ellipsoid be at the Earth's center of mass, that the shortest axis be parallel to the Earth's conventional axis of rotation, and that one of the other two axes be parallel to the plane of the meridian of Greenwich.
Industry:Earth science
