# coordinate system

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The Four Main Coordinate Systems
coordinate system

## coordinate system

() A system, resembling that of latitude and longitude on the Earth, by which the direction of a celestial body or a point in the sky can be specified. The direction is defined and determined by two spherical coordinates, referred to a fundamental great circle lying on the celestial sphere and a point on the fundamental circle (see illustration). One coordinate (a) is the angular distance of the celestial body measured perpendicular to the fundamental circle along an auxiliary great circle passing through the body and the poles of the fundamental circle. The other coordinate (b) is the angular distance measured along the fundamental circle from a selected zero point to the intersection of the auxiliary circle.

There are four main coordinate systems: the equatorial, horizontal, ecliptic, and galactic coordinate systems (see table). They are all centered on the Earth. Transformations can be made from one system to another by means of the relationships between the angles and sides of the relevant spherical triangles. The astronomical triangle, for example, relates equatorial and horizontal coordinates; the triangle formed by the celestial body and the poles of the equator and ecliptic relates equatorial and ecliptic coordinates. See also heliocentric coordinate system.

References in periodicals archive ?
So the satellite position in celestial co-ordinate system can be expressed as:
"This marks the first time since the observatory's creation that the geographic and geomagnetic co-ordinate systems have coincided at this location."
African regional and custom groupings could co-ordinate systems and approaches to deal with VAT and trade taxes, as other regional associations such as the European Union have done; this is an important need, given that intra-African trade is increasing at an annual rate of more than 10%.
It provides many more examples of concurrency of lines and circles constructed on geometric figures and on graphs in Cartesian and polar co-ordinate systems. The author thanks, among others, his students and preservice teachers for finding many of these examples.
"It is important to co-ordinate systems as, for example, a bus operating between Middlesbrough and Newcastle runs through three transport sub-regions and would need to communicate with three systems.
Features include many new toolbar options for model layout, including isometric grids and flexible co-ordinate systems, new grouping concepts for and a new "multi-designer" template for access to different market and application templates.
The motion of the rotational pole, which defines `true north', is studied using the International Reference Pole (IRP), a conventional `fixed pole' used in global co-ordinate systems. Relative to the IRP, the rotational pole performs a roughly circular motion with a diameter of about 15 metres, completing the circle about every 430 days.

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