- Branche: 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, ...
A constant change in the angle between the axis of rotation and the axis of figure. Secular polar motion was discovered by B. Wanach in 1916 from an analysis of the data on variation of latitude between 1900 and 1915. He found a motion of 0.003" per year along the 55<sup>o</sup> West meridian. Markowitz in 1960, from an analysis of more data found a value of 0.0032" per year along the 60<sup>o</sup> W meridian.
Industry:Earth science
A vertical or diagonal passage between levels to permit ore to be dropped from the one level to the other.
Industry:Earth science
(1) A corner established at the intersection of a township, range, or section line with the banks of a navigable stream or a body of water around which a meander line has been established. (2) A corner established at the intersection of a standard township or section line with the meander line near the banks of a navigable stream or a meanderable body of water.
Industry:Earth science
Convergent photography done so that the cameras' fields of view include the horizon.
Industry:Earth science
A grating placed in front of the objective lens of a telescope to produce stellar spectra. The image of each star in the field is then a short spectrum instead of a dot. The grating must be coarse to keep the spectra short and to reduce overlapping between neighboring images. Objective prisms are also used to produce stellar spectra.
Industry:Earth science
The equation of motion for a viscous fluid: it may be written dv/dt = (1/ñρ) Δρ + F + κ * Δ²v + ½ *Δ (*Δ.v), in which p is the pressure, Δ the density, F the total external force, v the fluid's velocity and κ the kinematic viscosity. For an incompressible fluid, the term in *Δ.v vanishes and the viscosity then plays a role analogous to that of temperature in thermal conduction and to that of density in simple diffusion. Analytical solutions of the Navier-Stokes equation have been obtained only in a small number of special cases. More general solutions are obtained by numerical methods.
Industry:Earth science
A quantity on which the results of an adjustment depend, but which does not appear as an unknown in the observation or condition equations. The concept appears to be equivalent to that called a hidden variable in quantum mechanics.
Industry:Earth science
The number m characterizing a celestial object of brightness b m, according to the formula m ≡ constant -2.5 log b <sub>m</sub>, in which the value of the constant depends on the assigned magnitude n and apparent brightness b <sub>n</sub> of another object taken as standard: constant ≡ n -2.5 log b <sub>n</sub>, so that m - n = -2.5 log (b <sub>m</sub> - b <sub>n</sub>). This defines the scale of apparent magnitudes except for the location of the zero point. The zero point of the scale of visual magnitudes is, by convention, found by assigning the magnitude +1 to the average brightness of the two stars Aldebaran and Altair. On this scale, the Sun has an apparent magnitude of -26.7. A star of first (visual) magnitude provides illumination of 2.43 lumens per square meter or 3.1 x 10<sub>-6</sub> ergs/cm²-sec. A star of sixth magnitude (just barely visible) sends 3000 photos per second into the eye (an aperture of 5.5 mm). A star of 21st magnitude (near the limit of telescopic visibility) sends approximately 0.01 photos per second into an area of 1 cm².
Industry:Earth science
A map showing a variety of geographical features (e.g., coastlines, political boundaries, transportation lines) and used for planning, location, reference, etc. A general map is contrasted with a thematic map and with a special purpose map.
Industry:Earth science
That plane which is defined by the ray incident on a surface and the normal to the surface at the point of incidence. The plane of incidence also includes the reflected or refracted ray, so it can be defined by any two of the three lines.
Industry:Earth science
