- Branche: 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, ...
Any plane containing the perspective center. Because the intersection of two planes is a straight line, the intersection of a perspective plane with a horizontal plane will always appear as a straight line in the photograph. Any straight line in object space will therefore also appear as a straight line in the photograph.
Industry:Earth science
A camera whose optical system consists simply of a small hole through which the light is admitted. A pinhole camera has extremely high geometric fidelity. However, its resolution is limited by diffraction. The very small aperture needed to ensure geometrical fidelity also cuts down the amount of light admitted, so that either very long exposures must be used or only very bright objects photo-graphed. It has been used for architectural photogrammetry, solar photography and other projects where very high accuracy is important. X-ray photographs are taken with pinhole cameras.
Industry:Earth science
A dynamic number calculated with the value of gravity calculated from a standard gravity formula rather than from the measured value.
Industry:Earth science
The angular coordinates of a celestial body in a heliocentric coordinate system, referred to mean equator and equinox of a standard epoch. A mean place is deter-mined by removing from the directly measured angular coordinates the effects of refraction, geocentric and stellar parallax, and stellar aberration and by referring the coordinates to the mean equinox and equator of a standard epoch (e.g., of date). Alternatively, it may be considered the result of removing from the apparent place the annual aberration and the annual parallax. In compiling star catalogs, it has been the practice not to remove the secular part of stellar aberration or the elliptic part of annual aberration.
Industry:Earth science
An orbit differing from another orbit considered standard or ideal for that same body. The perturbations are the differences between the actual orbit and the standard or ideal orbit. An osculating orbit at some suitable time is commonly selected as the standard. A Keplerian orbit chosen so that the average values of the perturbations are small is also often used.
Industry:Earth science
(1) A nearly polar orbit about the Earth, with a radius such that the satellite passes twice daily, at local solar time, over all places on the Earth having the same latitude. (2) An orbit with a radius and inclination such that the orbit maintains its initial orientation relative to the Sun. Sun-synchronous orbits are retrograde, having inclinations between 95.7<sup>o</sup> and 180<sup>o</sup> and altitudes up to 5980 km. E.g., a noon-midnight orbit can be selected to allow good photographic conditions for about one-half of every revolution, or a twilight orbit can be selected so that the satellite is never in shadow (allowing solar power to be used continuously). The relation between the average radius r of the orbit and the inclination i of the orbit is given, approximately, by 9.97(R/r)^3.5 cos i = -0.9856, in which R is the average radius of the Earth.
Industry:Earth science
A printing plate prepared from a drawing or scribed plate showing only one color and used for reproducing that part of the map to be printed in that one color.
Industry:Earth science
