Inertial reference unit
An inertial reference unit is a type of inertial sensor which uses gyroscopes and accelerometers to determine a moving aircraft’s or spacecraft’s change in rotational attitude and translational position over a period of time. In other words, an IRU allows a device, whether airborne or submarine, to travel from one point to another without reference to external information. They mainly have application in guided missiles.
Another name often used interchangeably with IRU is Inertial Measurement Unit. The two basic classes of IRUs/IMUs are "gimballed" and "strapdown". The older, larger gimballed systems have become less prevalent over the years as the performance of newer, smaller strapdown systems has improved greatly via the use of solid-state sensors and advanced real-time computer algorithms. Gimballed systems are still used in some high-precision applications where strapdown performance may not be as good.
