coordinate system

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The Four Main Coordinate Systemsclick for a larger image
The Four Main Coordinate Systems
coordinate systemclick for a larger image
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.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
Vectors of absolute linear velocity of the mass centers projected in reference coordinate system are: - for body 1:
Analysis of Table I and Table II shows, that the largest differences of the distinguished parameters determined for SE for PS with PhS and for PS without PhS are when condition number cond(G) is taken into account independently of the used coordinate system. Smaller differences of the distinguished parameters are for number of iterations [] and the smallest ones for ratio A.
Direction calibration is used to obtain the rotation angle between the visual coordinate system and the tool coordinate system around the X-axis of tool coordinate system, and the laser emission direction of laser displacement sensor [12, 13].
M-T is the air gap flux orientation coordinate system of the torque system.
However, the kinematics and control of the robot should be realized in the robot base coordinate system [R.sub.B] which is generated in the robot body.
UPML Wave Equation in Orthogonal Curvilinear Coordinate System. From the literature [17,23], we know that the form of diagonal matrix of the parameters in the orthogonal curve coordinate system is unchanged.
(4) Inner gimbal coordinate system O[x.sub.n][y.sub.n][z.sub.n]: the O[x.sub.n] -axis points to the target and coincides with the beam direction.
(i) Navigation coordinate system ([S.sub.n] - [o.sub.n][x.sub.n][y.sub.n][z.sub.n]): a local ENU (east-north-up) frame fixed to a world is selected as the navigation frame.
a/ Parameters of the classification vector [[bar.M].sub.j] for classes full, miss-2, miss-3, miss-5 b/ Pattern determination, fixed coordinate system and ROIs
This vector, which describes the response along the direction of maximum response of the r-axis accelerometer, is useful here because it can be expressed in the (x, y, z) coordinate system of the gimbal, as can the acceleration vector
where matrix [M.sub.HG] is the homogeneous transformation matrix from the fixed coordinate system H - xy to G- [x.sup.p] [y.sup.p] and [M.sub.GL] is the one from G - [x.sub.p][y.sub.p] to the moving coordinate system L - [x.sub.m][y.sub.m].
where C is a constant and [R.sub.j] is the Raman tensor of the phonon j in crystal coordinate system. Loudon derived the Raman tensors for each of the 32 crystal classes (symmetry point groups).

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