This is a type of plane sundial clock, with the clock plane perpendicular (vertical) to the earth surface at the sundial location. The shadow produced by the tip of the gnomon on the vertical clock plane is used to read the hour and the day.
The vertical clocks are classified into two subtypes; aligned and nonaligned (declining).
Aligned clocks have the normal of their plane and the plane of the gnomon in the plane of the local meridian of the location. Nonaligned clocks have the normal of their plane forming an angle with this meridian, called the orientation (decline) of the wall. This angle is usually measured from the south in the northern hemisphere and from the north in the southern hemisphere. The orientation is either easterly or westerly from true south and is common for both hemispheres.
This sundial includes a calendar, and the proper corrections for longitude, the equation of time, and daylight savings time, in order to obtain the correct civil time.
The geometric dimensions of the clock used in the program are input in the screen DIMENSIONS.
