How is compass error calculated?

Compass error is determined by calculating the difference between the true bearing (the actual direction to a navigational point based on true north) and the compass bearing (the direction indicated by the magnetic compass). This calculation allows navigators to identify how far off the compass reading is from the true direction. The concept of compass error is important for accurate navigation because it helps in correcting course and ensuring that the desired path is followed accurately.

By understanding that compass error is specifically the discrepancy between true north and the magnetic readings provided by a compass, navigators can make the necessary adjustments to account for inaccuracies caused by environmental factors, including magnetic variation (the difference between magnetic north and true north) and any deviation that may occur due to the vessel's magnetic fields. This distinction is crucial in navigation practices, ensuring safe and correct passage on the water.