- Industry: Earth science
- Number of terms: 93452
- Number of blossaries: 0
- 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 volume of water required to cover one acre to a depth of one foot. Equivalent to 43,560 cubic feet of water, it is a convenient unit for measuring the amount of water in a reservoir, the amount needed for irrigation, or the amount of runoff.
Industry:Earth science
The angle from the line of apsides of an elliptical orbit to a radius vector drawn from the center of the ellipse to that point on the circumscribed circle which lies on the same perpendicular (to the line of apsides) as the moving body. The point on the circle and the moving body therefore project onto the same point on the line of apsides. The eccentric anomaly is usually denoted by E; less often by η. It is related to the mean anomaly by Kepler's equation.
Industry:Earth science
A horizontal control datum in Africa, based on Cape datum and having presumably the same origin with the same coordinates and azimuth there. However, the vast longitudinal and latitudinal extent of the networks have caused complex modifications to take place during the calculations, and it is difficult to say exactly what datum or datums govern the networks. The Clarke 1880 spheroid (modified) is used for the most part, but triangulation in some former French territories has been on a datum using Clarke's values for a and b rather than his values for a and 1/f. There is a series of datums called Arc datum 1950, Arc datum 1960, etc. It is not clear to what extent these are different datums, different networks, or both.
Industry:Earth science
(1) The outlet of a lake. (southern U. S. A. ) (2) A small river or creek. (southern U. S. A. )
Industry:Earth science
A form of mean time used particularly in setting an astrograph (navigational device); 1200 hours mean time is set to occur when the local hour angle of the vernal equinox is 0°.
Industry:Earth science
That steric anomaly which would be reached if the pressure of sea water were changed isothermally to a standard pressure of one atmosphere. i.e., the steric anomaly with pressure terms omitted.
Industry:Earth science
Determining differences of elevation with respect to a specified surface from differences of atmospheric pressure measured with a barometer or from differences of altitude determined using a barometric altimeter. By applying certain corrections and using what is sometimes called the barometric formula, a difference of atmospheric pressure at two places is transformed into a difference of altitude at those places. If the elevation of one station above a reference surface is known, the approximate elevations of other stations connected with it by barometric altimetry can be calculated. By using barometers of special design, and by including several stations of known elevation in a sequence of occupied stations, the accuracy of the elevations determined for the new stations is increased. Corrections are applied for temperature, latitude, index of barometer, misclosure of circuit, diurnal variation in atmospheric pressure, etc.
Industry:Earth science
(1) Aerotriangulation using a mechanical, optical, or optomechanical model of the relationship between image point and object point. Two principal methods are used: the radial method, which obtains only the horizontal coordinates of the ground points; and stereotriangulation, which uses a stereoscopic plotting instrument to obtain horizontal coordinates, vertical coordinates or both. (2) The process of determining the location and orientation of the aerial camera at the times the photographs were taken. This meaning is rare.
Industry:Earth science
Conversion of the measured length of a base line to the length of a line lying on some other surface but having its end points on the same verticals or normals that pass through the end points of the base line. The surface chosen is usually the reference ellipsoid (base line reduction to the ellipsoid) but may be to an ellipsoid approximating an equipotential surface through mean sea level at some point (base line reduction to mean sea level) or to an ellipsoid approximating the geoid (base line reduction to the geoid).
Industry:Earth science
