Resolving range ambiguities in asynchronous underwater acoustic tracking system by reference to target position

For underwater acoustic positioning system based on measurement of time_delay, range ambiguity appears when pulse's propagating time is longer than its repetition period. Range ambiguity is an unavoidable problem in active high data rate underwater acoustic positioning system. Positioning system may work at asynchronous style when signal's emitting time is unknown. In this case a fixed time difference exists between emitter's and receiver's clock. This paper proposed the problem of resolving range ambiguities in asynchronous tracking system based on time_delay measurement and a software method of resolving ambiguities by target's reference location was brought forward. The equivalence rule was obtained from the pcsitioning model, and based on this rule the algorithm of resolving ambiguities and the responding reference scope were derived. The reference scope is large enough to ensure the method's feasibility and security, and the method has been proved to be valid by sea trial. This method not only has merits that hardware methods cannot hold, but also has a broader application space compared with the software methods in synchronous systems when the clock has low precision and even excursion.