On 20 June your vessel's 1955 ZT DR position is LAT 52°38.9'N, LONG 03°42.7'E, when an amplitude of the Sun is observed. The Sun's center is on the visible horizon and bears 311° per gyrocompass. Variation in the area is 6°W. At the time of the observation, the helmsman noted that he was heading 352° per gyrocompass and 358° per steering compass. What is the gyro error and deviation for that heading?

Question

Accepted Answer

Option C: 1.3°E GE, 1.3°E DEV. Calculate the Sun's true amplitude using the formula sin(Amp) = sin(Dec) / cos(Lat). With the Sun at the horizon, compare the true amplitude to the gyro bearing to find gyro error. Apply the gyro error to the gyro heading to find the true heading, then compare with the magnetic heading to derive deviation.