HRG gyrocompass

A HRG gyrocompass is a compass and instrument of navigation. It is the latest generation of maintenance-free instruments.
It uses a hemispherical resonant gyroscope, accelerometers and computers to compute true north. The HRG gyrocompass is a complete unit, which unlike a conventional compass, has no rotating or other moving parts. It has an outstanding reliability. Its operational Mean Time Between Failure (MTBF) values are improved over a Fiber Optic Gyrocompass and also conventional mechanical gyrocompass. 
It is also immune to severe environmental conditions.