Compass error is the sum of which two components?

• A. Declination and inclination
• B. Drift and tilt
• C. Deviation and variation
• D. Magnetic field strength

Answer: (C)

Compass error comes from two sources: deviation and variation. Deviation is the error caused by the ship’s own magnetic field and onboard electrical equipment influencing the compass. Variation, or magnetic variation, is the difference between true north and magnetic north at your location due to the Earth’s magnetic field. These two factors add together to give the total misalignment between a true course and what the compass shows. Other terms describe different magnetic properties (for example, inclination is the dip of the magnetic field, while magnetic field strength is a field property, not an error component).