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 gyro heading of 166°. 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 gyro heading of 166&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 A: 1.0&deg;W. Convert the gyro heading of 166° to True using 2°E error (168°T). Apply 8°W variation to find the magnetic heading (176°M). Interpolating the table for the corresponding PSC heading shows the compass reads 177°PSC. The difference between 176°M and 177°PSC confirms a deviation of 1.0°W for this heading.