- Branche: Earth science
- Number of terms: 93452
- Number of blossaries: 0
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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, ...
Any device using a spinning mass to establish or maintain a fixed direction. A spinning mass resists any attempt to change the direction in which the axis of rotation points. A torque applied to the mass and perpendicularly to the axis of rotation causes the axis of rotation to precess. Gyroscopes can therefore be used to find North (as in gyroscopic compasses and gyroscopic theodolites) or to maintain the orientation of a structure (as in inertial navigation systems.) The basic law governing the motion of a free gyroscope is dI ω / dt = T / I ω, in which I* is the vector giving the angular velocity of the spinning mass, T is the torque applied perpendicularly to axis of rotation, ω is the rate of rotation, I is the magnitude of the angular momentum and t is the time. The name gyroscope was applied to the device by Foucault in 1852
Industry:Earth science
The condensation gravity reduction in which the masses above the geoid are first transferred inside the geoid and as close to it as possible. The best method is to coat the masses onto the geoid (giving the ideele störende Schicht). The process is then sometimes called the Faye gravity reduction.
Industry:Earth science
(1) The quantity to be added to that used in the free air gravity reduction to take account of the fact that by removing matter between the geoid and the real surface, the position of the geoid is changed (lowered) so that masses now appear outside the geoid.
Industry:Earth science
The determination of altitudes by using a barometric altimeter. More usually called barometric altimetry.
Industry:Earth science
The quantity δg <sub>Honkasalo</sub> ≡ - k(1 - 3 sin²φ) added to a theoretical value of gravity (or subtracted from a measured value) to correct for the effect of a permanent Earth tide; this produces an increase of gravity with latitude φ. The value 0.037 for k gives δg <sub>Honkasalo</sub> in milligals.
Industry:Earth science
A combination of elevation and scale factors used to convert from distance on the ground to distance on the grid, or vice versa, in the State Plane Coordinate System or State Coordinate System.
Industry:Earth science
(1) A light (3-7 kg) lead attached usually to a line not more than 20 fathoms (about 40 meters) long. (2) A light (3 - 6 kg) sounding lead attached to a line usually less than or equal to 25 fathoms (about 46 meters). (3) The lead-line consisting of the lead and line referred to in the preceding definition.
Industry:Earth science
An optical device used by the pilot of a helicopter to assist him in hovering precisely over a marked point on the ground. The device consists of an auto-collimator mounted vertically on a silicon-damped pendulum. The image of the mark, on the autocollimator's reticle, is superposed on an image of the ground beneath.
Industry:Earth science
The gravity anomaly obtained by adding, to the measured value, the amount by which gravity is increased by removing all water at depths greater than 5 km and replacing it with rock of density 2.60 g/cm3, and replacing rock at depths less than 5 km by water.
Industry:Earth science
