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 147°T, and the variation is 5°E. If the heading of your vessel at the time of the sighting is 148° 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 147&deg;T, and the variation is 5&deg;E. If the heading of your vessel at the time of the sighting is 148&deg; per standard magnetic compass, what is the correct deviation?

Accepted Answer

Option D: 6&deg;W. Compass error is the difference between the true bearing and the compass bearing. With a true bearing of 147°T and a compass bearing of 148°psc, the error is 1°W. Subtracting the 5°E variation from the error (Error = Var + Dev) yields a deviation of 6°W, following standard piloting procedures.