Which statement best distinguishes Deviation from Variation?

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Understanding how these two influences affect compass readings helps answer this. Deviation comes from local magnetic interference—metal objects, machinery, or electrical equipment on the vessel that distort the compass’s magnetic field. This interference is specific to the ship and can change as gear or cargo changes. Variation, on the other hand, is a geographic difference: the angle between magnetic north and true north at a given location due to the Earth’s magnetic field. It’s a property of where you are, not what’s on your boat.

So the best statement separates the two by saying deviation is caused by metal near the compass, while variation is caused by the difference between Magnetic North and True North. This captures that deviation is local interference, and variation is a regional magnetic field effect.

For context, deviation is corrected by calibrating the compass and creating a deviation card (swinging the compass) to account for onboard interference. Variation is corrected in navigation calculations by applying the variation value to magnetic bearings to obtain true bearings, or by using charts that show the local variation.