方位角又称地平经度（Azimuth，缩写Az），是在平面上量度物体之间的角度差的方法之一。

假若两者加上与目标的距离，就会成为极坐标：直角坐标系（笛卡尔坐标系）以外的另一种坐标系统。

An azimuth (/ˈæzɪməθ/) (from Arabic al-sumūt, meaning "the directions") is an angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and a reference vector on the reference plane is called the azimuth.