 Gyroscope, the gyroscope is a device used for measuring or maintaining orientation and angular velocity. It is a spin wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting. According to the conservation of angular momentum, gyroscopes based on other operating principles also exist, such as the microchip packaged MEMS gyroscopes found in electronic devices, solid state ring lasers, fiber optic gyroscopes, and the extremely sensitive quantum gyroscope. The applications of gyroscopes include inertial navigation systems, such as in the Hubble telescope, or inside the steel hull of a submerged submarine. Due to their precision, gyroscopes are also used in gyroheodolites to maintain direction in tunnel mining. Gyroscopes can be used to construct gyro compasses, which complement or replace magnetic compasses in ships, aircraft and spacecraft, vehicles in general to assist in stability bicycles, motorcycles, and ships or be used as part of an inertial guidance system. MEMS gyroscopes are popular in some consumer electronics, such as smartphones.