Gyrotheodolite
![A Wild GAK gyroscope mounted on a Wild T-16 theodolite.](/Images/godic/202501/16/WildT16+GAK_sept19892309.jpg")
A gyro-theodolite is a surveying instrument composed of a gyroscope mounted to a theodolite. It is used to determine the orientation of true north. It is the main instrument for orientation in mine surveying and in tunnel engineering, where astronomical star sights are not visible.