Question 647Navigation General

The correct answer is B) variation and deviation. When changing from a compass course to a true course, you need to apply both variation (the angle between true north and magnetic north) and deviation (the angle between the compass needle and the magnetic north) to convert the compass course to a true course. Variation is a geographic correction that accounts for the difference between true north and magnetic north, while deviation is a compass-specific correction that accounts for local magnetic disturbances. The other options are incorrect because: A) Applying a correction for current set is only necessary when converting between compass course and water course, not when converting between compass course and true course. C) Variation alone is not sufficient, as deviation must also be accounted for. D) Deviation alone is not sufficient, as variation must also be accounted for.