Your vessel is proceeding up a channel, and you see a pair of range lights that are in line ahead. The chart indicates that the direction of this pair of lights is 352°T, and the variation is 4°W. If the heading of your vessel at the time of the sighting is 359° per standard magnetic compass, what is the correct deviation?

Question

Your vessel is proceeding up a channel, and you see a pair of range lights that are in line ahead. The chart indicates that the direction of this pair of lights is 352&deg;T, and the variation is 4&deg;W. If the heading of your vessel at the time of the sighting is 359&deg; per standard magnetic compass, what is the correct deviation?

Accepted Answer

Option A: 3&deg;W. True heading is 352°. Magnetic heading is True minus Variation (352 - (-4) = 356°M). With a compass heading of 359°C, the deviation is the difference between Magnetic and Compass. Since the compass reads higher than magnetic, the deviation is 3°W (Compass Best, Magnetic Least, Error West).