Bistatic Localization of Objects in Very Shallow Water

Ting Zhang,T C Yang,Wen Xu

doi:10.1109/access.2019.2947851

Abstract

Bistatic or multi-static systems use spatially distributed sources and/or receivers to ensonify scattering objects over a distance to obtain the acoustic images of individual targets for classification purposes. The targets need to be localized first and separated from the clutter. To reach targets at a distance, low frequency sound is often used; targets can in principle be classified based on the frequency and azimuthal angle response of the echo return, referred to as acoustic color. Practical application of this technology is limited by the array size and the ability to localize the target and extract the scattering echo. Deconvolution of conventional beamforming (CBF) has been shown to achieve a narrow beam width and low side lobe levels equivalent to CBF of an array of much larger aperture. This method is applied to active sonar in this paper. Analysis of simulated and tank experimental data demonstrated a better separation of targets and a higher target-to-reverberation ratio than that using CBF.

Highlights

Underwater imaging technology has wide applications in ocean exploration and other fields, such as pipe and cable survey, bridge pillar inspection, fish detection, mine classification, etc
Bistatic detection and classification of bottom laid, partially and fully buried objects were carried out in very shallow water (VSW) using a rack-mounted horizontal line array (HLA) and/or an array mounted on an autonomous underwater vehicle (AUV) as the receiver [1]–[4]
To compare clutter returns for sources at different positions, we show in Fig. 11(d) the deconvolved CBF (dCv) beam energy versus angle and time, and in Fig. 11(e) the dCv localization map in Cartesian coordinate based on data from the source at position 4 (x = 0, y = 25.3 m)

Summary

INTRODUCTION

Underwater imaging technology has wide applications in ocean exploration and other fields, such as pipe and cable survey, bridge pillar inspection, fish detection, mine classification, etc. Low frequency (e.g., 20 kHz or less) sonar has been recently proposed to extend the detection range to hundreds-to-thousands meters It could provide a high rate for target detection over a large area. To extract the acoustic color, the target needs to be localized and separated from the strong reverberation return This requires a beamformer that produces a narrow beam width. Bistatic detection and classification of bottom laid, partially and fully buried objects were carried out in very shallow water (VSW) using a rack-mounted horizontal line array (HLA) and/or an array mounted on an autonomous underwater vehicle (AUV) as the receiver [1]–[4].

PROBLEM FORMULATION

EXPERIMENTAL DATA ANALYSIS

SUMMARY AND CONCLUSION