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Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere.
This is then subtracted from 90° to obtain the angular distance from the position directly above to obtain the zenith distance. A further correction must then be taken into account to counter the "wobble" of the earth's spin and rotation relative to the sun and planets.
To compute the greatest distance D BL at which an observer B can see the top of an object L above the horizon, simply add the distances to the horizon from each of the two points: D BL = D B + D L For example, for an observer B with a height of h B =1.70 m standing on the ground, the horizon is D B =4.65 km away.
Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon. The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth.
Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction. Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the Earth. [1]
Azimuth: the direction angle within the plane of the horizon, typically counted clockwise from the north (in geodesy and astronomy) or the south (in France). Elevation: the angular height of an object above the horizon; alternatively: zenith distance equal to 90 degrees minus elevation.
Celestial navigation by taking sights of the Sun and the horizon whilst on the surface of the Earth is commonly used, providing various methods of determining position, one of which is the popular and simple method called "noon sight navigation"—being a single observation of the exact altitude of the Sun and the exact time of that altitude ...
The fundamental plane is the plane of the Earth's equator. The primary direction (the x axis) is the March equinox. A right-handed convention specifies a y axis 90° to the east in the fundamental plane; the z axis is the north polar axis. The reference frame does not rotate with the Earth, rather, the Earth rotates around the z axis.