- 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 variant of the arc method of adjusting a triangulation network, in which the length and azimuth of one side of a triangle at every junction between arcs (chains) are assumed correct and carried into a suitable figure at the junction. Directions or angles in arcs between these figures are then calculated, the corrections in the individual chains calculated, and the misclosures passed into the longitudes and latitudes of the initially fixed sides in the junctions by an adjustment of the entire network, using the method of least squares. The method was devised in the Coast and Geodetic Survey, under the direction of William Bowie, for the adjustment of large triangulation-networks.
Industry:Earth science
(1) The quantity gBe obtained by subtracting from a gravity anomaly Δg the free air gravity correction δg <sub>f</sub>, the spherical Bouguer gravity correction δg <sub>Bs</sub>, and the topographic gravity correction δg <sub>t</sub>: Δg <sub>Be</sub> ≡ Δg - δg <sub>f</sub> - δg <sub>Bs</sub> - δg <sub>t</sub>. Equivalently, the quantity obtained by subtracting from the spherical Bouguer gravity anomaly the topographic gravity correction. The topographic gravity correction is introduced because of the difference between the actual distribution of mass ignored in applying the free air correction and that assumed by introducing the spherical shell. (2) The result of subtracting, from a Bouguer gravity anomaly with topographic correction, a further gravity correction to account for the curvature of the Earth. This is practically, if not exactly, equivalent to using a spherical Bouguer gravity anomaly with topographic correction. The expanded Bouguer gravity anomaly is also called the complete Bouguer gravity anomaly and the refined Bouguer gravity anomaly. The latter term, however, seems to be applied also to the Bouguer gravity anomaly with topographic correction.
Industry:Earth science
A method primarily of determining geodetic azimuths from astronomical observations, by measuring the angle θ' between a star and the marker of interest, the star and marker being at large zenith distances z* and z<sub>m</sub>, respectively. The difference between measured angle θ'and the corresponding angle θ in a geodetic coordinate system is θ' - θ = cotz* (y cos A* - x sin A*) - cot z<sub>m</sub> (y cos A<sub>m</sub> - x sin A<sub>m</sub>) where x and y are the deflections of the vertical in the meridian and in the prime vertical, respectively; A* and A<sub>m</sub>m are the astronomic azimuths of the star and marker, respectively. The astronomic azimuth of the star is given by A* = sinφ cot H - tanδ cosφ cosec H, where φ is the latitude of the observer and H and δ are the hour angle and the declination, respectively, of the star. At large zenith distances, θ'- θ is very small, and the geodetic azimuth is given closely by the second equation. If it is not small, three or more observations are made on different stars to determine x and y also. The method is particularly useful at high latitudes. The method has also been used to determine astronomic latitude and longitude.
Industry:Earth science
A false coloring of an image, usually caused by chromatic aberration.
Industry:Earth science
(1) A document, usually given to the buyer of a home with the deed, stating that the title to the property is clear. It is usually prepared by an attorney or qualified person who has examined the abstract of title for the property. It is only an opinion that title is good and is not to be confused with title insurance. (2) A certificate issued to show title registered on lands covered by Torrens title.
Industry:Earth science
A body which keeps its shape regardless of the forces imposed upon it. No actual bodies are completely rigid, but the concept is convenient in mechanics. For example, a good, approx-imate theory of oceanic tides can be derived by assuming that the lithosphere is a rigid body and that only the oceans yield to the attractions of the Moon and Sun.
Industry:Earth science
A traverse which relies on the magnetic compass for orienting the traverse as a whole of for determining the directions of individual lines.
Industry:Earth science
A document which evidences that an entryman is entitled to a patent provided that no irregularities are found in connection with his entry.
Industry:Earth science
The line passing through the second nodal point of the objective of a telescope and perpendicular to the axis of rotation of the telescope. In a surveyor's transit or theodolite, the collimation axis is perpendicular to the horizontal axis of the telescope. In a leveling instrument, it is perpendicular to the standing axis (vertical axis) of the instrument. When the telescope of a transit or theodolite is rotated about its horizontal axis, the collimation axis describes a plane called the collimation plane.
Industry:Earth science
