| Abstract from DBPedia | An azimuth (/ˈæzəməθ/; from Arabic: اَلسُّمُوت, romanized: as-sumūt, lit. 'the directions') is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematically, the relative position vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane (the horizontal plane); the angle between the projected vector and a reference vector on the reference plane is called the azimuth. When used as a celestial coordinate, the azimuth is the horizontal direction of a star or other astronomical object in the sky. The star is the point of interest, the reference plane is the local area (e.g. a circular area with a 5 km radius at sea level) around an observer on Earth's surface, and the reference vector points to true north. The azimuth is the angle between the north vector and the star's vector on the horizontal plane. Azimuth is usually measured in degrees (°). The concept is used in navigation, astronomy, engineering, mapping, mining, and ballistics.方位角（ほういかく、英語: azimuth）とは、方位（方向の水平成分）の数値表現であり、基準となる方位との間の角度のことを言う。 航空分野においては、機首の方向や進行方向を示すのに用いられる。 水平座標系や天測航法、また衛星通信用地上アンテナの光軸方向を示すときには、水平方向の方位角と、垂直方向の仰角という2つの角度を用いる。 角度の単位は測量や航法などの分野においては標準的には度・分・秒が用いられる。 (Source: http://dbpedia.org/resource/Azimuth) |
