Variation in a magnetic compass is determined by what?

• A. Where you are on the Earth's surface
• B. The vessel's speed
• C. The time of day
• D. The weather

Answer: (A)

Variation is the angular difference between magnetic north and true north at your location. This depends on where you are on the Earth's surface because the Earth's magnetic field is not aligned with the geographic poles and varies across latitude and longitude. So the amount and direction of variation change as you move from place to place. Speed, time of day, and weather don’t set this angle (though intense magnetic storms can cause temporary compass wobble, that’s a separate effect).