- Branche: 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 method of finding particular values of a set of randomly variable unknowns by requiring that the entropy - Σ p <sub>i</sub> log p <sub>i</sub> of the set of probabilities p <sub>i</sub> associated with the unknowns x <sub>i</sub> be a maximum. The method has been applied mostly to determining the frequencies present in signals that can be represented as a mixture of frequencies, i.e., in spectral analysis.
Industry:Earth science
A satellite of a planet. The word is not capitalized when used in this sense, e.g., a moon of Mars or an artificial moon.
Industry:Earth science
The horizontal-control datum in the Philippine Islands which is defined by the following coordinates of the origin and by the azimuth (clockwise from South) on the Clarke spheroid of 1866; the origin is at triangulation station Balanacan:<br>
Industry:Earth science
That method (of observing an artificial satellite) in which measurements are made from four or more stations simultaneously; the locations of at least three of the stations with respect to each other must known.
Industry:Earth science
A map that provides a large variety of information and satisfies the needs of many different kinds of users.
Industry:Earth science
Determining the coordinates of an observer from observations on a satellite over a portion of the orbit so long that the orbit must be represented by as faithful a set of equations as possible. A long arc method is usually considered to require more than a quarter of one complete revolution of the satellite. Anything less than this is treated by the short-arc method.
Industry:Earth science
A method of solving for the location of a survey station by first deriving the orbit of a satellite from observations made at stations elsewhere and then using observations on the satellite from the survey-station, together with the known orbit, to derive the location of the station. The survey station's location is found in the coordinate system used for the locations of the stations whose data were used in determining the orbit. Two variants of this method are in common use: the short-arc method and the long-arc method. In the short arc-method, the stations used for determining the orbit observe the satellite shortly before or after the survey station. A very short part of the actual orbit is therefore used, and this can usually be approximated by a curve much simpler than the actual orbit. In the long-arc method, the stations determining the orbit observe long before and long after the survey station. The orbital mode is distinguished from the simultaneous mode in that the latter requires that observations be made simultaneously by the survey station and by the stations whose coordinates are known. No orbit need be determined in this method.
Industry:Earth science
A map containing information of two or more general types. A composite map is usually a compiled map, bringing together for comparison data originally shown on separate maps. For example, a map showing air-routes and roads would be a composite map, particularly if the air-routes and roads had originally been shown on separate maps.
Industry:Earth science
Map projection mapping the three great arcs of a spherical triangle on the sphere as straight lines on the plane and laying off, from the vertices of the planar triangle, the true distances, to scale, of points on the sphere. To each point on the sphere then corresponds a small triangle in the plane. The center of each small triangle is taken as the representation of the corresponding point on the sphere. This map projection, developed by W. Chamberlin, has been used for a number of maps published by the National Geographic Society.
Industry:Earth science
