Chart Navigation & Plotting · Compass & Course
Compass deviation is caused by:
- AThe difference between true and magnetic north
- BThe earth's rotation
- CMagnetic influences within the vessel acting on the compass✓ Correct
- DErrors in the chart's compass rose
Explanation
Deviation is the compass error produced by the vessel's own magnetic fields — steel, electronics, and equipment — and it changes with the vessel's heading. Variation, in contrast, is a property of the earth's field at that location, independent of the vessel.
Authority: Bowditch, Pub. No. 9 (magnetic compass)
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