Glossary term: 高度角
Description: 高度有兩種含義：一是指在某種坐標系中的特定角度，如“恆星的高度角”，二是指相對於給定參考水平的垂直距離，如“海拔高度5000米”。
在天文學（以及測量學）中，高度角是所謂地平坐標系中的一個角度。這個角度衡量的是天體距離地平線有多高——如果你用手指指向一個天體，然後將手指直下移動到地平線處，那麼你的手臂的方向就會發生變化，變化的角度就是高度角。高度角可以用度或弧度來測量。位於地平線的天體，其高度角為0°；而位於頭頂正上方（即所謂“天頂”）的天體，其高度角為90°。負的高度角表示當前位於地平線以下的天體——此處，高度角測量的是天體在地平線以下的距離。位於你腳底正下方（即所謂“天底”）的天體，其高度角為-90°。
在航空或大氣物理學等其他領域，海拔高度是指一個位置比某個給定的參考水平面高出多少。在地球上，海拔高度通常被定義為平均海平面以上的高度。根據這一含義，海拔高度是以長度單位（例如如米）來衡量的。
Related Terms:
See this term in other languages
Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
This is an automated transliteration of the simplified Chinese translation of this term
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
If you notice a factual or translation error in this glossary term or definition then please get in touch.
Related Diagrams
Horizontal Coordinate System
Caption: This image shows the horizontal coordinate system of an observer on Earth. On the right we see the coordinate system in the local context of the observer. The observer appears here as a point surrounded by the celestial sphere. The ground appears as a plane, while the Earth is round, we can approximate the ground in the area around the observer as a plane. The line where this plane intersects with the celestial sphere is the horizon. The point directly above the observer is the zenith, the point directly below the observer is the nadir which is hidden by the ground.
Two coordinates define this coordinate system, altitude and azimuth, hence the reason this sometimes called an alt-az coordinate system. The altitude is zero at the horizon, maximum (90°) at the zenith and minimum (-90°) at the nadir. Azimuth is the angle around the horizon. Most commonly this is defined to be zero in the direction of north. Any point on the celestial sphere can be defined by these two coordinates. However what objects appear on these position will depend on the time and the location of the observer.
On the left-hand part of the diagram, we can see that when we put the observer and their local horizontal coordinate system in a global context, that the parts of the sky the observer can see depend on their position on the Earth and on the rotation of the Earth. The zenith points perpendicular to the Earth's surface so the position on the sky the zenith and nadir correspond to is dependent on the observer's latitude. The horizon also depends on the observer's position on the Earth.
Credit: Maria Cristina Fortuna/IAU OAE
License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (CC BY 4.0) icons
