You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2°E. The variation is 8°W. Find the deviation on a magnetic compass heading of 104°. HEADING PSC-PGC 030.5°-020° 061.5°-050° 092.0°-080° 122.5°-110° 152.0°-140° 181.0°-170° 210.0°-200° 239.5°-230° 269.0°-260° 298.0°-290° 327.5°-320° 358.5°-350°

Question

You swung ship and compared the magnetic compass against the gyro compass to find deviation. Gyro error is 2&deg;E. The variation is 8&deg;W. Find the deviation on a magnetic compass heading of 104&deg;. HEADING PSC-PGC 030.5&deg;-020&deg; 061.5&deg;-050&deg; 092.0&deg;-080&deg; 122.5&deg;-110&deg; 152.0&deg;-140&deg; 181.0&deg;-170&deg; 210.0&deg;-200&deg; 239.5&deg;-230&deg; 269.0&deg;-260&deg; 298.0&deg;-290&deg; 327.5&deg;-320&deg; 358.5&deg;-350&deg;

Accepted Answer

Option C: 2.2&deg;W. Convert PGC to True using 2°E gyro error (True = PGC + Error). At 104°T, interpolate the table to find the PSC heading. Applying the variation (8°W) to the True heading yields the Magnetic heading. The difference between Magnetic and Compass headings provides the deviation, calculated here as 2.2°W.