Description
The Vertical sundial has two main parts: the Gnomon and the Vertical sundial shadow-receiving plane. Vertical sundial shadow-receiving plane is aligned vertically and the gnomon is positioned in a way that it aligns with the Earth’s axis of rotation.
If the wall of the building faces toward the South, but does not face due South, the gnomon will not lie along the noon line, and the hour lines must be corrected. Since the gnomon’s style must be parallel to the Earth’s axis, it always “points” true North and its angle with the horizontal will equal the sundial’s geographical latitude; on a direct south dial, its angle with the vertical face of the dial will equal the colatitude, or 90° minus the latitude.
The gnomon of Vertical sundials is often a single metal bar, but may also be a tripod of metal bars in order to help provide rigidity.