compass error correction
For the last couple of classes, my junior class has been focusing on compass error correction. Compasses have been used for thousands of years to point north. The magnetic field at Magnetic North is strong enough to attract the needle in the compass to point at it.
However, Magnetic North and True North are different points. This degree difference, variation, changes according to where you are and the year. Any inconsistency in a compass can be very significant. If you are navigating between underwater rocks, even a couple degrees can lead to disaster. Compasses is not always accurate. They can be influenced by the metal on the boat you are on. This difference is called deviation.
To find the Compass Course you need to point your boat towards, you must go through some simple calculations. A good way to remember this process is True-Variation-Magnetic-Deviation-Compass.