When determining true south, the key thing to remember is that the times reflected on a clock do not necessarily match up with what is actually happening. This means that it is necessary to make a few basic observations and calculations, starting with determining when the sun is at its highest point in the sky. Then, by using any object, a compass and calculating magnetic declination, you can determine true south in a matter of minutes.
- Determine when the sun is at its highest point in the sky
Although noon is traditionally thought of as when the sun is at its highest point, noon as the clock reads is not necessarily an accurate reflection of this occurrence. Instead, find the times for the sunrise and the sunset, and then determine the time exactly in the middle. This is the point of the day at which the sun is at its highest.
- Use an object to identify the shortest shadows
When the sun is at its highest point, track an object's shadow to determine when it is at its shortest. When the shadow is at its shortest, the sun is in perfect true north and true south alignment. To determine an object's shortest shadow, it may be necessary to make several markings reflecting the size of the shadow and then find the marking that is the closest to the actual object.
- Calculate magnetic declination
Magnetic declination refers to the distance of a location from the meridian line in a time zone. Magnetic declination can be determined using a compass and a location's latitude and longitude. If latitude and longitude are unknown, there are multiple tools on the Internet to aid in making this determination. Turn the compass the number of degrees in the direction indicated from the meridian. The compass is then pointing true north and true south.