The technique or method of directing a carrier from a starting point to a destination is called navigation. The navigation system measures and resolves the instantaneous motion state and position of the vehicle, providing the driver or autopilot for proper manipulation or control of the vehicle. With the development of science and technology, more and more navigation information sources are available, and there are more and more types of navigation systems. Taking aerial navigation as an example, the available onboard navigation systems include inertial navigation systems, GPS navigation systems, Doppler navigation systems, Roland C navigation systems, etc. These navigation systems have their own characteristics, advantages and disadvantages coexist. For example, the advantage of inertial navigation (hereinafter referred to as inertial navigation) system is that it does not require any external information and does not radiate any information. It can be navigated under any medium and any environmental conditions, and can output the position, speed and orientation of the aircraft. And a variety of navigation parameters such as attitude, the frequency bandwidth of the system, can track any maneuvering motion of the vehicle, the navigation output data is stable, and the short-term stability is good. However, inertial navigation systems have inherent disadvantages: navigation accuracy diverges over time, ie, long-term stability is poor. The navigation accuracy of the GPS navigation system is high. After the US Department of Defense joins the SA (Selective Availa bility) error, the horizontal and vertical positioning accuracy of the C/A code signal can still reach 100 and 157 m, respectively, and does not diverge with time. Long-term stability is beyond the reach of inertial navigation systems. However, the GPS navigation system also has its Achilles heel: the frequency band is narrow. When the carrier makes a high maneuvering motion, the code ring and carrier ring of the receiver are easily lost and lose the signal, thus completely losing the navigation capability; relying entirely on GPS satellite transmission. Navigation information is subject to others and is subject to human interference and spoofing. The remaining navigation systems also have their own advantages and disadvantages.
When various navigation systems are used alone, it is difficult to meet the navigation performance requirements. An effective way to improve the overall performance of the navigation system is to use integrated navigation technology, that is, to measure the same navigation information with two or more non-similar navigation systems. The solution is used to form a volume measurement from which the errors of each navigation system are calculated and corrected. The system using integrated navigation technology is called integrated navigation system, and participates in the combined navigation system called subsystem.
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