cylindrical coordinate system

A cylindrical coordinate system with origin O, polar axis A, and longitudinal axis L. The dot is the point with radial distance ρ = 4, angular coordinate φ = 130°, and height z = 4. The reference plane contains the purple section.

A cylindrical coordinate system is a three-dimensional coordinate system that specifies point positions around a main axis (a chosen directed line) and an auxiliary axis (a reference ray). The three cylindrical coordinates are: the point perpendicular distance ρ from the main axis; the point signed distance z along the main axis from a chosen origin; and the plane angle φ of the point projection on a reference plane (passing through the origin and perpendicular to the main axis)