- Отрасли: Earth science
- Number of terms: 93452
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- 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, ...
The window of optical quality, in an aircraft, through which aerial photographs are taken. The quality of the camera port has a significant effect on the quality of the photographs taken.
Industry:Earth science
An instrument which allows two standards of length to be compared by substituting the one standard (bar) for the other in the instrument.
Industry:Earth science
The direction indicated by the north-seeking end of the needle or other magnetic component of a magnetic compass. It differs from magnetic north, the direction of a magnetic line through the point of observation, by the amount that the supports and housing of the magnetic compass affect the needle's movement.
Industry:Earth science
The Newton Cotes formula for N = 4. Simpson's rule is preferred to Boole's rule for simplicity; Weddle's rule is preferred for both accuracy and simplicity.
Industry:Earth science
One of a set of numbers and a system of coordinates, introduced by Bessel, for predicting the progress of solar eclipses and of occultations. The coordinate system has its origin at the center of mass of the Earth. The z-axis is drawn in the direction of the Moon and parallel to the line joining the centers of the Sun (or other star) and the Moon. The y-axis lies in the plane of the z-axis and the North Pole and is positive northwards. The x-axis is drawn to complete a right handed, rectangular Cartesian coordinate system. The Besselian elements are then the following: (a) the coordinates (x,y) of the center of the Moon's shadow on the (x,y) plane (eclipse) or the right ascension and declination (áα*, δ*) of the star (an occulation); (b) the rates of change (x',y') of x and y per hour; (c) the Universal Time or Ephemeris Time To of conjunction in right ascension of the Moon and star (occultations only); (d) the hour angle μ of the z-axis at the Greenwich meridian (eclipses) or the hour angle H of the star at Greenwich at the instant To (occultations); (e) the declination d of the z-axis (eclipses) or the value Y of the y coordinate at the instant To (occultations). The quantities α*, δ*, x', y', To, H and Y are the Besselian elements of an occultation. The quantities x, y, x', y', μ, sin d and cos d, together with the following quantities peculiar to eclipses, are the Besselian elements of an eclipse; (f) the quantity dμ/dt (μ'); (g) the radii l<sub>1</sub> and l<sub>2</sub> of the umbral and penumbral cones on the (x,y) plane; (h) the angles f<sub>1</sub> and f<sub>2</sub> (half the vertex angles of the penumbral and umbral cones, respectively. The Besselian elements both for eclipses and for occultations are usually given in astronomical almanacs. However, many almanacs, because interest in eclipses and occultations has decreased and because calculating machines can easily calculate some of the elements, no longer list all the elements. (Some authors consider only x, y, x', y', μ, sin d and cos d to be Besselian elements of an eclipse. )
Industry:Earth science
A boundary between countries. Such a boundary is established by the sovereign powers concerned.
Industry:Earth science
The formula adopted in 1930 by the International Association of Geodesy and called the International Gravity Formula.
Industry:Earth science
Source material used as a guide by the compiler and/or draftsman in preparing a map or chart and consisting, usually, of details on roads, railroads, cities, and the like that have been developed from field surveys. It is usually furnished in the form of overlays, annotated maps, drawings, photographs or field sheets.
Industry:Earth science
The plane described by the collimation axis of the telescope of a transit or theodolite when the telescope is rotated around a horizontal axis.
Industry:Earth science
