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 Earth's magnetic field shifting slowly over time
- ✓ The vessel's own magnetism, and it changes with the vessel's headingCorrect
- C. The geographic position of the vessel on the chart
- D. The difference between true north and grid north on the chart projection
Why B is correct
Deviation is caused by the vessel's own magnetic properties and changes as the vessel's heading changes. It is read from the vessel's deviation card. Variation, by contrast, is a property of the Earth's field at a given location and changes with position and time.
Cited:Bowditch Ch. 6 §601