中文摘要：

介绍一种利用水声信道的统计不变特征（波导不变量）实现被动测距的方法。对接收LOFAR（Low Frequency Analysis Record）图使用HOUGH变换等边缘提取技术提取条纹，得到波导不变量以及抛物线参数的估计值，进而得到目标的CPA（Closest Point of Approach）点距离。矢量水听器的振速通道数据所得LOFAR图信噪比明显高于声压LOFAR图，可以提高测距精度。仿真和试验数据结果显示本方法能以较高的精度提取CPA点距离。对比波导不变量经验值和在线估计值所得最近点距离结果，发现使用具有一定精度的在线估计波导不变量值可以显著提高测距精度。

英文摘要：

A passive ranging method is proposed based on waveguide invariant. The receive Low frequency analysis record （LOFAR） spectrum contain parabola striations when the wideband target pass by the Closest Point of Approach （CPA）. We can extract the striations Through suitable image processing technique such as HOUGH transform, and then derive the waveguide invariant, finally estimate the range of the target. Vector LOFARgram contain particle velocity information has higher SNR than scalar LOFARgram which can improve the precision of range estimate. The method can estimate the range of the CPA with high precision for both simulation and experimental data. In estimating the CPA range, both the experience value and the measuring value of the waveguide invariant are used, result show that the measuring value is more credible.