An angular measurement, usually measured in degrees, within a spherical coordinate system. Derived from the Arabic “as-sumut” or “the directions”. As a celestial coordinate, it’s the horizontal direction of an astronomical object in the night sky, for example, using the star as a point of interest and the local area as the reference plane, while truth north serves in this example as the reference vector. The term first came into use in the 14th Century. It’s used in navigation, astronomy, engineering, mapping, and ballistics.
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