Navigation General · Compass - Magnetic
Magnetic compass deviation is caused by:
- AThe Earth's magnetic field varying by location
- BThe rotation of the Earth
- CThe magnetic influence of iron and electrical equipment within the vessel itself✓ Correct
- DTidal currents
Explanation
Deviation is the error introduced by the vessel's own magnetic field (steel structure, machinery, wiring). It changes with the ship's heading and is recorded on a deviation table or card; variation, by contrast, is a property of the Earth's field at that location.
Authority: Bowditch (Pub. 9); magnetic compass
Practice the full Navigation General bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Navigation General questions
- Compass - Magnetic
Compass deviation differs from variation in that deviation:
- Dead Reckoning
A vessel departs a known position at 0800 on course 090°T at 12 knots. What is the DR position at 1100?
- Time-Speed-Distance
Using the 60 D = S × T formula, how long will it take a vessel traveling at 15 knots to cover 45 nautical miles?
- Time-Speed-Distance
A vessel travels 90 nautical miles in 6 hours. What is the vessel's speed?
- Dead Reckoning
Which of the following is the best definition of a Dead Reckoning (DR) position?
- Set & Drift
A vessel steers 000°T at 10 knots for 2 hours. The observed position shows the vessel is 4 nm east of the DR position. What is the set and drift of the current?