Navigation systems are used for land, sea, airborne, and space vehicles. These systems provide an operator and/or control system with the necessary information to effect some action in response to data provided by these systems. For example, this action can be a course correction indication for an aircraft pilot or a feedback control signal to guide an autonomous vehicle. These systems incorporate onboard sensors coupled with a computer, permitting self-contained operations with little or no assistance required from sources external to the vehicle.

The core of the navigation system is a set of sensors combined with a computer that can provide a relatively stable and accurate source of navigation. These systems output navigation state data, which usually include position, velocity, and attitude. As a result of imperfections in navigation sensors and computational errors, errors develop in the navigation state data and grow in time. The host vehicle's operating environment also influences the error growth rate. Long-term error growth is minimized by including other sensors that provide independent redundant navigation data, i.e., position, in an integrated system that optimally combines this independent data source with the core navigation system. These independent sensors, referred to as navigation aids, are characterized by long-term error stability, which can compliment the short-term error stability of the navigation system's sensors. When combined within a computer algorithm, such as a Kalman filter, errors from both the core sensors and navigation aids can be estimated to reduce the integrated navigation system's errors. The resulting navigation system will exhibit...