- Industria: 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, ...
An azimuth chosen as a matter of convenience, usually by assigning north south line in a survey as the meridional direction, or by defining an east west line as being at right angles to the meridional direction.
Industry:Earth science
A compensating base line apparatus composed of a bar of iron and a bar of brass, each a little less than 6 meters in length, held together firmly at one end, with the free ends so connected by a compensating lever as to form a compensating base line apparatus.
Industry:Earth science
The angle between the plane of the hour circle passing through a celestial body and the plane of the hour circle passing through the vernal equinox. It is measured eastward from the vernal equinox through 24 hours (1 angular hour equals 15° ) or 360°. It may also be defined as the angle, at the celestial pole, between the tangents to the hour circles of the celestial body and of the vernal equinox. Right ascension and declination form a pair of coordinates that conveniently specify the location (direction) of a body on the celestial sphere. It is conventionally represented by <font face = symbol>a</font>.
Industry:Earth science
A telescope containing illuminated crosshairs placed so that they are imaged, by the objective lens system, at infinity (i.e., light from it is collimated by the objective lens system). When the telescope is aimed at a flat reflector placed approximately perpendicular to the telescope's optical axis, the crosshairs and their reflected image can be viewed together through the telescope's eyepiece. The reflected image will be displaced from the direct image by twice the angle between the optical axis and the perpendicular to the reflector.
Industry:Earth science
That apparent change in direction of a star, planet, or other celestial body which is caused principally by the Earth's revolution about the Sun. That part of stellar aberration which has an annual period. (The Sun's barycentric motion combines with the Earth's revolution to cause a very small aberration which is also covered by the term. ) During the year, a star in the plane of the Earth's orbit (the ecliptic) appears to move from one end of a straight line to the other and back again. The length of this line is twice the constant of aberration. A star 90° from the ecliptic appears to move in a circle which has a diameter twice the constant of aberration. Stars at intermediate angles above or below the ecliptic appear to move in ellipses with major diameters twice the constant of aber-ration and with minor axes getting longer with increasing angular distance of the star from the ecliptic. Because the Earth moves in an elliptical rather than a circular orbit, the apparent paths of stars not on the ecliptic are not quite elliptical.
Industry:Earth science
(1) A vector which has a length is equal to the magnitude of a given plane angle and which is directed so that it is perpendicular to the plane of that angle and in a sense so as to form a right handed system with the sides of the angle.
(2) The angle between the fixed line to which a direction is referred and a radius vector.
Industry:Earth science
An instrument used for determining depths of the oceans or other deep bodies of water. There are a number of designs of such instruments. The principal ones are the lead line and the echo sounder.
Industry:Earth science
A direction determining machine into which the coordinates of a celestial body can be set, together with the observer's latitude, and which then indicates astronomic north, azimuth and heading.
Industry:Earth science
Voluntary surrender or relinquishment of possession in real property without vesting this interest in another person.
Industry:Earth science
