- 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) The average value of the quantity x(r+nh) and y(nh), where x and y are randomly varying functions of the quantity nh and n being an integer which varies from N to +N and r and h are constants. (2) The limit of the quantity defined in (1) as N becomes very large. (3) The average value φ(r) defined by (1/2T) ∫ x(r+t)y(t) dt. (4) The limit of the quantity φ(r) defined in (3) as T goes to infinity. If x and y are different variables, the correlation function is called the cross correlation function of the two variables. If they are the same variable, it is called the auto correlation function of x.
Industry:Earth science
(1) The geographic locations at which measurements of current are made. (2) The facilities used to make measurements of current at a particular site. These may include a buoy, ground tackle, current meters, recording devices and radio transmitter.
Industry:Earth science
The largest amount (annual aberration), in theory, by which a star's apparent direction varies during the year solely because of the Earth's revolution about the Sun. It is commonly denoted by κ and is given by the formula κ = 2π a/(cT (1 - e²)½) , in which a is the length of the semi major axis of the Earth's orbit, e is the eccentricity of that orbit, T is the length of the sidereal year and c is the speed of light in space. For the epoch 2000 A. D. , κ has the value 20. 495 52 (I. A. U. 1977).
Industry:Earth science
The difference between the two corresponding angles formed by the intersection of a geodesic with two different meridians. Sometimes abbreviated to convergence or convergency. It may also be defined as the difference in forward and back azimuths at the two ends of a geodesic. At the equator, all meridians are parallel - they make the same angle, 90<sup>o</sup>, with the equator. Passing north or south from the equator, two meridians converge until they meet at the poles, intersecting at angles equal to their differences of longitude. If the surface involved is spherical, the quantity is called spherical convergence; if it is a rotational ellipsoid (spheroid), it is called spheroidal convergence.
Industry:Earth science
An easterly and westerly property line adjusted to the same average bearing from each monument to the next one in regular order, as distinguished from the long chord or great circle that would connect the initial and terminal points.
Industry:Earth science
A quantity added to the time of the chronographic signal of a stellar transit observed using an electrically recording, impersonal micrometer, to allow for the time required for the contact spring to cross half the width of a contact strip in the head of the micrometer. In order to ensure a satisfactory signal, the contact strips are given an appreciable width. As the micrometer wire travels from different sides of the instrument at upper and lower culminations, and also before and after reversal of the instrument, the contact spring produces a signal sometimes from one edge of a contact strip and sometimes from the other. The contact correction is intended to produce the time that would have been recorded if the electrical signal had occurred only when the contact spring crossed the middle of the contact strip.
Industry:Earth science
The loss in value of the remainder of a piece of property, resulting from the acquisition of a part of the property.
Industry:Earth science
A sketch showing how the prints of the transformed photographs taken by a multiple-lens camera should be changed to get the equivalent of a single photograph made by a single-lens camera. The sketch gives distances referred to the fiducial marks on the photographs and is the result of the calibration of the particular camera used.
Industry:Earth science
(1) A positive photograph on a transparent substance, usually plastic or glass. The term generally refers to a transparent positive on a glass plate, used in a stereoscopic plotter, a projector, or a measuring engine (comparator). In Europe, it usually refers to a positive film transparency which would be identified as a slide by an American user.
(2) A photographic image external to the aerial camera by which it was formed.
Industry:Earth science
A formula giving the effect of errors in the measured angles and lengths in a geometric figure on the error in an angle or length calculated from the measured values. Often referred to as GDOP. The name refers to the well known fact that the error which results in calculating the value of an angle or length in a geometric figure from the values of other angles and lengths depends very much on the values of those other angles and lengths. There are firm rules set for the shapes allowable in planning a triangulation network, based on this fact.
Industry:Earth science
