You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2°W. The variation is 8°W. Find the deviation on a magnetic compass heading of 166°. HEADING PSC-PGC 030.5°-024° 061.5°-054° 092.0°-084° 122.5°-114° 152.0°-144° 181.0°-174° 239.5°-234° 269.0°-264° 210.0°-204° 298.0°-294° 327.5°-324° 358.5°-354°

Question

You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2&deg;W. The variation is 8&deg;W. Find the deviation on a magnetic compass heading of 166&deg;. HEADING PSC-PGC 030.5&deg;-024&deg; 061.5&deg;-054&deg; 092.0&deg;-084&deg; 122.5&deg;-114&deg; 152.0&deg;-144&deg; 181.0&deg;-174&deg; 239.5&deg;-234&deg; 269.0&deg;-264&deg; 210.0&deg;-204&deg; 298.0&deg;-294&deg; 327.5&deg;-324&deg; 358.5&deg;-354&deg;

Accepted Answer

Option B: 1.5&deg;W. Convert the magnetic compass heading of 166° to True using the 8°W variation (158°T). With a 2°W gyro error, the PGC is 160°. Interpolating the table for this heading confirms the deviation is 1.5°W, ensuring the magnetic compass is correctly adjusted for the vessel's current magnetic signature and local variation.