- 行业: 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 leveling instrument whose telescope and level are connected rigidly to a vertical axle, so that the line of sight must be leveled using the screws in the base (or using the compensator). A contrasting variety is the tilting level.
Industry:Earth science
The celestial reference system determined by ignoring small variations of short period in the motions of the celestial equator and ecliptic. Coordinates in stellar catalogs are normally referred to the average catalog equinox and equator of the beginning of a Besselian year.
Industry:Earth science
A suspension of a light-sensitive salt of silver (especially silver chloride or silver bromide) in a colloidal medium (usually gelatin, which is placed as a coating on rigid or flexible materials such as glass plates, plastic film, or paper to be used in photography. It is usually referred to simply as the emulsion, although it is not a true emulsion. Types in common use are panchromatic (producing black and white pictures), color negative (producing pictures in colors complementary to those of the object), color positive (producing pictures in colors the same as those of the object), infrared-color (producing pictures in which infrared radiation from the object is represented by colors in the picture), and infrared black and white (producing pictures in which the density of a spot in the picture is proportional to the amount of infrared illumination radiation that has illuminated that spot).
Industry:Earth science
An ephemeris which contains coordinates and times (and possibly velocities) more precise than those of a broadcast ephemeris. The term has been used, in particular, to refer to the ephemerides of the TRANSIT satellites. Those ephemerides are prepared from data received from several tracking stations over the world and are calculated with great precision using the method of least squares.
Industry:Earth science
An ellipse containing exactly 50% of a set of points having a bivariate Gaussian distribution. The equation of the ellipse is (ξ/σ<sub>x</sub>)² 2ρ(η/σ<sub>x</sub>) (η/σ<sub>y</sub>) + (η/σ<sub>y</sub>)² = (1 - ξ²)κ ², in which κ ² is such that (1 - exp(- κ ²/2)) is exactly 0. 5. σ<sub>x</sub> and σ<sub>y</sub> are the standard deviations and ρ is the correlation coefficient. κ² is approximately 1. 1777.
Industry:Earth science
The ellipse which is the intersection of an ellipsoid with a plane through the center of the ellipsoid and perpendicular to a line oblique to the axes of the ellipsoid.
Industry:Earth science
Hydrostatic equilibrium assumed to be present over a very small oceanic area.
Industry:Earth science
(1) The elevation resulting from adding an adjustment correction to an orthometric elevation. (2) The elevation resulting from adding both an orthometric correction and an adjustment correction to a preliminary elevation.
Industry:Earth science
(1) The difference in hour angle between mean solar time and apparent solar time. An equivalent definition is the difference between the hour angle of the true Sun and the hour angle of the mean Sun. As the equation of time may be expressed as a correction to either apparent solar time or to mean solar time, its sign must be observed carefully. (2) The difference between mean and apparent time. From the beginning of the year until near the middle of April, mean time is ahead of apparent time, the difference reaching a maximum of about 15 minutes near the middle of February. From the middle of April to the middle of June, mean time is behind apparent time but the difference is less than 5 minutes. From the middle of June to the first part of September, mean time is again ahead of apparent time, with a greatest difference less than 7 minutes. From the first part of September until the latter part of December, mean time is again behind apparent time, the difference reaching a maximum of nearly 17 minutes in the early part of November. The analemma is a graphical display of the equation of time.
Industry:Earth science
A cube-corner reflector used in distance measurement by electro optical distance measuring.
Industry:Earth science
