What does deviation refer to in navigation?

Deviation in navigation specifically refers to the error introduced in a vessel's compass due to magnetic interference from the ship itself. This is particularly important when determining the true course and ensuring safe navigation.

While 'error in course the boat is trying to steer' seems to suggest deviation, it doesn't accurately describe what deviation means in navigational terms.

The correct understanding of deviation indicates how the onboard magnetic compass may not provide an accurate reading due to local magnetic fields created by electronic equipment or other magnetic materials on the vessel. Therefore, deviation must be accounted for when determining the vessel's true heading, particularly when navigating under varying magnetic conditions.

In contrast, the other definitions relate to different navigational concepts. The difference between true and magnetic north refers to magnetic variation, not deviation. Actual distance traveled pertains to the distance covered over a certain period, and change in speed over time refers to acceleration and does not relate to navigation errors.

Understanding the nuanced definitions helps in grasping the significance of compass corrections and maintaining an accurate course at sea.