Search results
Results From The WOW.Com Content Network
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.
[3] [a] In practice, the horizon can be defined as the plane tangent to a quiet, liquid surface, such as a pool of mercury, or by using a bull's eye level. [4] The pole of the upper hemisphere is called the zenith and the pole of the lower hemisphere is called the nadir. [5] The following are two independent horizontal angular coordinates:
Angular distance appears in mathematics (in particular geometry and trigonometry) and all natural sciences (e.g., kinematics, astronomy, and geophysics). In the classical mechanics of rotating objects, it appears alongside angular velocity, angular acceleration, angular momentum, moment of inertia and torque.
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]
Geometrical horizon distance. 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.
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
Instead of the radial distance r geographers commonly use altitude above or below some local reference surface (vertical datum), which, for example, may be the mean sea level. When needed, the radial distance can be computed from the altitude by adding the radius of Earth, which is approximately 6,360 ± 11 km (3,952 ± 7 miles).
The difference between this measurement and the nadir point was the nadir distance of the star. A movable horizontal wire or declination-micrometer was also used. [11] Another method of observing the apparent altitude of a star was to take half of the angular distance between the star observed directly and its reflection observed in a basin of ...