USCG Exam PracticePlotting with variation and deviation (T-V-M-D-C)
Deviation differs from variation in that deviation is caused by which of the following?
- A. The geographic position of the vessel relative to the magnetic pole
- ✓ The vessel's own magnetism and changes with the vessel's headingCorrect
- C. Annual secular change in the earth's magnetic field
- D. The difference between grid north and true north on a Mercator chart
Why B is correct
Deviation is the angle between magnetic north and the vessel's own compass north, caused by the vessel's magnetism; it changes with the vessel's heading and is read from the deviation card. Variation, not deviation, is tied to geographic position and secular change.
Cited:Bowditch Ch. 6 §601