Gyrocompasses

Gyrocompasses or gyros are instruments that measure the rotation or heading of a device. Usually, an Inertial Navigation System INS is composed by an Inertial Measurement Unit IMU in which there are usually 3 accelerometers and 3 gyroscopes to measure the acceleration in the 3 directions of the space and the rotation in the 3 axes. Normally these 6 elements are arranged in a cluster in an orthogonal instrument. 

There are different types of gyros, such as the mechanical Dynamically tunned gyroscope DTG, the ring laser gyro RLG, the fiber optic gyro FOG, and the Micro Electrical Mechanical Sensor Gyro MEMS.  

Typically, the mechanical gyros have a measuring range of 500°/sec and are quite huge, while RLG gyros have a measurement range of 1000°/s, and although are more expensive they offer a very good accuracy, and are used for aerial photogrammetry, aerospace, and submarines. On the other hand, the FOG gyros have a measurement rate of up to 1000°/s, have a good accuracy and are used in surveys and vessels. Finally, the MEMS gyros are the cheaper and smaller solution, although these offer less accuracy, they can be successfully implemented in cars and microdrones.