Solar compass

The solar compass uses the movement of the sun to indicate North (or rather South in the Northern Hemisphere). It is an astronomic device which does not rely on anything but the knowledge of the movement of the sun. Essentially the principle is that at noon (local solar time) the sun is due South. However, for this the exact moment the sun is highest in the sky must be determined. For moments in between South can still be determined but this requires some knowledge of time (longitude) and location (latitude). Most solar compasses use a set of scales to solve for this problem.