What is magnetic variation?

Master the Navigation, Seamanship, and Shiphandling (NSS) – Officer of the Deck (OOD) Phase 2 Exam with engaging flashcards and multiple choice questions, complete with hints and explanations. Prepare comprehensively for your test!

Multiple Choice

What is magnetic variation?

Magnetic variation is the angular difference between magnetic north and true north. This means it’s the angle you must account for when converting a bearing or course from the geographic (true) reference to the direction indicated by a magnetic compass (magnetic heading), or vice versa. The value varies by location and changes over time (secular variation), and on charts it appears as the current variation with its rate of change. This differs from grid north, which is based on the map’s projection lines, not the Earth’s magnetic field, and from deviation, which is the error introduced by the vessel’s own magnetic influence on the compass. The statement that best matches magnetic variation is the angular difference between magnetic north and true north.

Magnetic variation is the angular difference between magnetic north and true north. This means it’s the angle you must account for when converting a bearing or course from the geographic (true) reference to the direction indicated by a magnetic compass (magnetic heading), or vice versa. The value varies by location and changes over time (secular variation), and on charts it appears as the current variation with its rate of change.

This differs from grid north, which is based on the map’s projection lines, not the Earth’s magnetic field, and from deviation, which is the error introduced by the vessel’s own magnetic influence on the compass. The statement that best matches magnetic variation is the angular difference between magnetic north and true north.

More practice questions