Glossary of Principal Terms

Inertial navigation systems rely on complex technology, even if the implementation is simple or mundane. Thus it will be inevitable that many technology specific terms and jargon will be in common usage. The more common aspects are covered here together with those that are used in the text of this book. The terms described appear in alphabetical order.

Accelerometers

These devices are used to measure the translational motion of the vehicle in which they are located. In its most basic form, this sensor consists of a proof mass attached, via a spring, to the case of the instrument. The device operates by detecting a displacement of the mass in the presence of an acceleration of the vehicle. An accelerometer actually provides a measure of specific force, the non-gravitational force per unit mass to which it is subjected.

Aiding

This technique refers to the use of external measurement data to enhance the performance of an inertial navigation system. The source of the aiding may be external to the vehicle or derived from an additional on-board sensor. An example of the former type is the use of position information provided by a tracking radar to update periodically an inertial navigation system in a short range tactical missile. Alternatively, an on-board sensor such as a Doppler radar or a barometric altimeter may provide information to aid the inertial system. As with all such techniques which combine measurement data with different characteristics, sophisticated Kalman filtering techniques are often used, and...