The Sun as a position finder: Simple determination of latitude
 
Set up a simple sharp vertical gnomon to cast a shadow on to a horizontal plane having a surface on which the shadow tip can be marked. At intervals of about ten minutes, over a period of about one hour either side of the local noon, mark the position of the shadow tip. After the recordings are completed, measure the minimum shadow length from the base of the gnomon to the shadow tip. This corresponds to the time when the Sun is on the meridian. Knowing the height of the gnomon above the horizontal plane allows the maximum altitude to be determined using the formula
.
Knowing also the Sun’s declination for that day, the latitude of the observer may be determined from


Figure 1. The simple determination of latitude.