Target detection method of side scan sonar

Abstract

The invention discloses a target detection method of a side scan sonar. The target detection method of the side scan sonar can effectively reduce an image noise and a small noise caused by factors such as scatter from water surface or water and furthermore has advantages of high processing efficiency and high detection accuracy. According to the target detection method, a weighted average template based on a 3*3 window is used for performing low-pass filtering on the image of the side scan sonar, thereby effectively eliminating a scattering noise caused by reasons of water surface scattering or in-water scattering in the image, and reducing processing stress and complexity for subsequent processing. Then a K means algorithm is utilized for classifying the pixels of the sonar image to a target kind and a shadow kind and generating two kinds of different images, thereby facilitating subsequent processing to the target and the shadow and improving processing efficiency. Furthermore a pyramid increase / reduction algorithm is used for eliminating the small noise in the image. Finally phony targets are further eliminated according to the area of a suspected target, the area of a corresponding suspected shadow and a ratio between the area of the suspected target and the area of the corresponding suspected shadow, thereby improving detection accuracy.

Description

technical field [0001] The invention relates to the technical field of digital image processing, in particular to a side-scan sonar target detection method. Background technique [0002] With the development of science and technology and the in-depth study of autonomous underwater robots, sonar technology has been developed by leaps and bounds. The attention and research on imaging sonar is also rapidly maturing. There are already acoustic holographic imaging test systems close to optical image quality, sonic mirror imaging systems, etc. Although the quality of acoustic images obtained by these imaging systems is good, they are not suitable for real environments. . The underwater open environment in practical applications has high requirements for sensors, which need to accurately perceive the real information of the surrounding environment. Active sonar (Activesonar) is the most widely used detection equipment for autonomous underwater vehicles, and side-scan sonar is one...

AI Technical Summary

Problems solved by technology

[0003] Although side-scan sonar images, like optical images, are essentially planar or spatial distribution maps of energy, due to the complex and changeable characteristics of underwater acoustic channels, as well as the projection and scattering characteristics of sound waves, their images is very different from the optical image

The side-scan sonar image in the underwater environment mainly has the following characteristics: (1) The resolution is low, the wavelength of the detection sound wave emitted by the sonar detection device is generally longer, and the detection step angle is relatively large, and the adjacent beams do not change continuously Yes, there is a certain interval, resulting in low resolution of sonar images; (2) Noise interference is serious, the underwater acoustic channel and the ocean environment are complex and changeable, and there are attenuation, reverberation, and scattering interferences in the sound wave propagation process. Other sounds in the marine environment are also the main source of sonar image noise, and targets are often submerged in these disturbances, making it difficult to detect; (3) Multipath phenomenon, which is caused by the propagation of sound waves in the process of propagation, making A target has multiple return values, resulting in ghosting in the image, making it difficult to determine the true position of the target; (4) side lobes, when the sonar beam is formed, in addition to forming a maximum value on the narrow main lobe , its side lobe will receive signals in a wide range, so when a certain echo is strong, a bright line of echo will be formed at the same distance from the nearby beam, that is, side lobe interference; (5) Doppler Le effect, when the target moves or the robot moves, the emitted and received sound waves will have a certain offset, and the same target will get different outlines on the sonar image at different times, thus causing deformation and distortion of the target

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