Explain the underlying principles of gyro surveying and describe the process of determining true north in an underground mine environment where GPS signals are unavailable.

Gyro surveying is a surveying technique used to determine the direction of true north in environments where GPS signals are unavailable, such as underground mines. It relies on the principle of gyroscopic inertia and the Earth's rotation. Gyroscopic inertia is the tendency of a spinning object to maintain its orientation in space. A gyroscope consists of a spinning rotor mounted on gimbals, which allow it to rotate freely in three dimensions. When the gyroscope is set in motion, its rotor will tend to resist any changes in its orientation. As the Earth rotates, the gyroscope will experience a torque, which is a rotational force, that causes it to precess. Precession is the slow, conical motion of the gyroscope's spin axis. The direction of precession depends on the orientation of the gyroscope relative to the Earth's ....