By tracking the Sun, we can determine local true noon (the point at which the sun is highest in the sky), which can differentiate from the local standardized time by nearly up to an hour, depending on one's location in a time zone. In the northern hemisphere, the difference in degrees between the bearing of the Sun and magnetic south at local true noon in turn determines true south; this difference is called the Sun's azimuth. Thus, a celestial navigator could use a quadrant and the Sun to calibrate a compass.
Of course, overcast skies can prove a serious annoyance, since they hide a navigator's celestial reference points. This holds true whether you're just trying to observe the sun for a project or a sailor lost at sea in the Northern Atlantic. Fortunately, we enjoyed clear skies during our data collection layover.