Moving target parameter estimation and passive ranging based on waveguide invariant theory

The interference striation equation of the target in intermediate or short range has been derived combining with the concept of waveguide invariant,indicating that the striations are a family of quasi-hyperbolas in the shallow water.The waveguide invariant β,which reflects the environmental information,the heading angle φ and r₀/v,which is the ratio of the range of the closest approach point to the target velocity,can be estimated by processing the LOFARgram and time-bearing display using Hough transform.Both the simulation and sea-trial data analysis results show that stable interference structure of the low-frequency sound field can be observed and high accurate parameter estimation for moving target can be obtained by adopting a means of image processing.Passive ranging could be achieved based on the double elements model,and the simulation results show that the algorithm has higher positioning accuracy and better robustness.