Gyroscopic compasses, or gyrocompasses, rely on a rapidly spinning gyroscope. They offer several advantages over traditional magnetic compasses, which rely on the earth's magnetic field.
Because of their steadiness and accuracy, gyrocompasses helped warships to search for and attack submarines. They also allowed the use of more advanced anti-submarine weapons. Master compasses like the example shown here could, in addition, send compass information to "repeaters" at various locations throughout a ship. Canadian corvettes did not start receiving gyrocompasses until mid-war. Until then, they had relied on magnetic compasses, which reduced their effectiveness as escorts and anti-submarine vessels.