﻿ Azimuth

# Azimuth

The ( also ) Azimuth ( from Arabic السموت, DMG as- sumut that way ', plural of السمت / as- velvet / ' the path ' ) is a term used in astronomy, one oriented according to the compass horizontal angle referred to. The term is, mutatis mutandis, also used in other fields.

## The azimuth in astronomy and geodesy

The definition of astronomy is as follows: The azimuth is the angle between the meridian plane and the vertical plane of a star.

In astronomy, the azimuth is counted starting from the south on the west, so that a star in the south, an azimuth of 0 ° and a star in the West has an azimuth of 90 °, or from North to East. The former is the original astronomical counting because if a point with equatorial right ascension a is at the meridian, it is a clock sidereal time ( simple conversion Horizon to equatorial system ). The second option is the system in geodesy and navigation generally accepted, because it was the North Pole always easy to determine (via the North Star ) ( and then the azimuth is the true bearing ) - This system is increasingly also in astronomy through. It is usual then for the four main points ( cardinal points) N 0 ° (0); O 90 ° ( π / 2); S 180 ° ( π ), W 270 ° ( 3π / 2). It is thus generally, looking from the zenith to the nadir, opposite to the Earth's rotation in the mathematically negative sense counted (clockwise), so the rotation of the apparent rotation of the celestial sphere to the observer, as he actually sees. Analogous measures in the Southern Hemisphere of South east ( the latter more system in the above sense, respectively from north west in the former sense) what the local - " mirror-image " - course of the sun and heavenly bodies from east to west across northern equivalent. But there are also systems in use, which are shown respectively in the other direction of rotation. Therefore always look for in azimuth information on the precise definition of the underlying coordinate system.

To calculate the azimuth of a star for a given time and a given observation site using the navigational triangle ( also called Astronomical triangle ). The azimuth of a star is only valid for a certain time and a certain place of the earth's surface.

The Geodesy knows except this astronomical azimuth, which can be determined by measurements according to fundamental stars accurate, even the ellipsoidal azimuth. This is the direction in a survey network, based on a reference ellipsoid of land surveying or at an average Erdellipsoid calculated up to 0.01 " ( arc seconds ) exactly. Astronomical and ellipsoidal azimuth differ by the east- west component of the deflection of the vertical. in the Gauss -Krüger coordinate system angles are specified, refer to grid north ( high - or x -axis). the reason for the difference between the celestial and terrestrial systems lies in the precise definition of the zenith on the local gravity vector ( plumb line ), or the surface normal ( perpendicular ) of the ellipsoid, and analogous to the exact north.

The methods for azimuth determination are the subject of Astro Geodesy; the most important for practical measurement methods are the Polaris azimuth (by Polar Star) and the solar azimuth. Individual measurements of celestial bodies can about 0.1 "just be ( equivalent to 5 mm to 10 km), with longer series of measurements more accurate. Azimuths sun reach only 1-5 ​​seconds of arc, but are won quickly and have the advantage of daytime viewing.

## Azimuths in the navigation and Technology

In the navigation ( maritime, air ) is called the azimuth between point and destination point course to steer, as opposed to actually driven course over ground. Nautical the azimuth is based on the north (see also culmination). So for the southeast is the azimuth in terms of a nautical course exactly 135 degrees, 225 degrees West.

In celestial navigation is meant azimuth of a star with the angle at the gegissten location ( paired site) from north through east to the image point ( base point ).

In cartography is meant by the azimuth angle measured clockwise between geographically -Nord ( North Pole ) and an arbitrary direction (eg marching direction magnetic compass bearing, etc. ) on the earth's surface.

In the artillery azimuth is the exact indication of direction in line ( artillery parts per thousand ).

In the antenna technology ( satellite radio ), the azimuth angle, the horizontal alignment of an antenna, as opposed to the elevation that specifies the vertical angle between the horizon and the antenna direction.

For wind turbines, the term azimuth is used for anything that has to do with the horizontal wind tracking of the nacelle. The yaw system is used for tracking of the nacelle and consists of yaw bearing, yaw drive, yaw drives and azimuth control. Azimuth drive consists of multi-stage planetary gears that are driven by frequency-controlled electric motors.

In tape recorders, tape recorders and audio equipment to the optical film projectors measured in the band plane angle between the Tonkopfspalt and the direction orthogonal to the belt running direction is referred to as azimuth. This angle should ideally be equal to zero, otherwise it is an azimuth error. To produce the correct azimuth of the tape heads are accordingly adjusted.

In solar technology is (at least north of the equator) denotes the deviation of the solar collector from south azimuth. -45 ° means southeast exposure, 0 ° and 45 ° south facing southwest exposure of the collector.

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