On 28 July your 1937 zone time DR position is LAT 26°13.0' N, LONG 78°27.0' E. At that time, you observe Deneb bearing 048.7°pgc. The chronometer reads 02h 37m 42s, and the chronometer error is 00m 15s fast. The variation is 4°W. What is the gyro error?

Correct Answer: Option D — 2.8°E

Finding GMT via chronometer and error allows extraction of geographic position for Deneb. Solving the navigational triangle determines true bearing (pgc equivalent). The algebraic difference between true bearing and gyro bearing establishes the gyro error of 2.8°E.