- 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, ...
A cylindrical box containing two vertical mirrors, one of which can be rotated through 60„a about a vertical axis. The movable mirror is turned by a knob at the top of the box and, as it rotates, so does an external pointer which indicates, on a metallic, graduated arc, the angle turned. The largest angle measurable is 120<sup>o</sup>. The instrument is best used for approximate but rapid measurement of horizontal angles in a reconnaissance for a later survey.
Industry:Earth science
The difference between the photographic and photovisual magnitudes of a star or, more generally, the difference between the magnitudes of a single star in two separate and specified regions of the spectrum. By convention, the color index (C. I. ) is then defined as: magnitude in short wavelength region minus magnitude in long wavelength region. The C. I. for an A0 star is defined in the Johnson Morgan UBV system of stellar classification to be zero. The C. I. of the Sun is 0. 62. The color index appears in geodesy when the coordinates of stars are to be determined very accurately from stellar photographs. It is one of the quantities appearing in the equations used in reducing the measurements of the photographs.
Industry:Earth science
A manufacturer's term for the spindle or spindles which are vertical when the leveling instrument is in used, and about which the leveling instrument, or a part of it, rotates.
Industry:Earth science
A composite printing, on glass, of the drawing of contour lines and drainage used on the shadow projector for checking the horizontal accuracy of landforms to be shown on relief models.
Industry:Earth science
The curve whose equation is y = k cosh(x/k), where k is a constant. A homogenous, perfectly flexible, inelastic cable, tape, or wire will, when suspended from two fixed points at its ends, assume this curve. If the density of the cable is d and the force of gravity is g, then the distance y' of a point on the cable from the ground is y' = h + (k/dg) cosh(xdg/k), where h and k are constants.
Industry:Earth science
The quantity P<sub>i</sub> / (Σ P<sub>i</sub>), where P<sub>i</sub> (i = 1,2,3) is the amount of a primary color required to give, by additive mixture with the other two primary colors, a match to the color desired.
Industry:Earth science
(1) The outer part or edge of anything; margin, verge. (2) A boundary. (3) A frontier of a state or of the settled part of a country; a district on the frontier.
Industry:Earth science
Bringing the center of an instrument vertically above a specified mark, using an optical device that allows the observer to view the point with the instrument or its mounting in place. The device itself is called an optical plummet, because it replaces the leaden plummet formerly used for centering instruments.
Industry:Earth science
A chart showing by arrows and numbers the average direction and speed of tidal currents at a particular part of the currents' cycle. A number of such charts, one for each hour of the currents' cycle, are usually published together.
Industry:Earth science
The most general map projection producing the least distortion in representing longitudinal distances. It was invented by Chebychev in 1856.
Industry:Earth science
