Definition
Deviation arises from permanent magnetism in the hull and engine, induced magnetism in soft iron, and stray fields from loudspeakers, electronics and portable devices. Unlike variation, it changes with the vessel's heading rather than with position, and so must be tabulated on a deviation card against each heading. It is named East when the compass north points clockwise of magnetic north. A well sited and compensated compass on a small yacht should show deviation of only a few degrees.
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