What does "variation" refer to in navigation terms?

In navigation, "variation" specifically refers to the angular difference between the true meridian and the magnetic meridian at a particular location on the earth. This is important because mariners need to account for this difference when using a compass, which points toward magnetic north rather than true north. Understanding variation helps navigators accurately determine their true heading and course over the ground, ensuring safer and more precise navigation.

Recognizing the distinction between true and magnetic directions is crucial, as it can significantly affect navigational calculations and decisions. The amount of variation can change depending on the geographical location and may also evolve over time due to changes in the Earth's magnetic field. Navigators typically refer to charts that provide information about local variation to make necessary adjustments in their bearings and course plotting.