A HRG gyrocompass is a compass and instrument of navigation.
It uses a hemispherical resonant gyroscope (HRG), 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 outstanding reliability. Its operational mean time to failure (MTBF) values are improved over a fibre optic gyrocompass and also conventional mechanical gyrocompass.
It is also immune to severe environmental conditions.
References
https://www.shephardmedia.com/news/digital-battlespace/uscg-patrol-boat-gets-safrans-bluenaute-system/