In
mathematics, a
spherical coordinate system is a
coordinate system for
three-dimensional space where the position of a point is specified by three numbers: the
radial distance of that point from a fixed origin, its
polar angle measured from a fixed
zenith direction, and the
azimuth angle of its
orthogonal projection on a reference plane that passes through the origin and is orthogonal to the zenith, measured from a fixed reference direction on that plane.