Target detetction in Clutter for sonar imagery

本课题旨在研究基于三维和纹理分析的水下目标检测与分类新技术。在平坦沙等简单的海底类型上，很容易对目标进行探测和分类。当海床上布满岩石或珊瑚结构、海藻等海洋生物或性质复杂（大型岩石露头和沙丘）时，这就变得困难得多。在这些区域，经典的目标检测和分类技术失败了，因为它们往往集中在目标的形状上，经典的使用阴影分析来恢复（声阴影是由目标在海底投射的）。另一方面，由于传统的高分辨率声纳容易受到散斑噪声的影响，并且通常分辨率不足以进行分类，因此对目标回波进行分析是困难的。在这种具有挑战性的场景中，可以通过将目标检测为当前纹理域中的异常值来改进检测和分类。这可以使用2D或3D纹理测量来完成，但由于大多数强烈的纹理是由于海底的3D性质，我们认为3D纹理分析将更有效，因此建议将重点放在这些上。分类可以通过开发新的高分辨率声纳（SAS）和新的3D声纳（干涉式SAS /侧扫）来解决。随着分辨率的提高，回声的结构将变得更加明显，并且可以使用机器视觉和模式识别社区开发的技术。这是本建议的次要目标。

This proposal aims at studying new techniques for detection and classification of targets underwater using 3D and texture analysis. On simple seabed types such as flat sand, it is very easy to detect and classify targets. It becomes much more difficult when the seabed is either highly cluttered with rocky or coral structures, marine life such as seaweed or is of a complex nature (large rocky outcrops and sand dunes). In those areas, classical target detection and classification techniques fails as they tend to concentrate on the shape of the target, classically recovered using shadow analysis (the acoustic shadow is casted by the target on the seabed). On the other hand, the analysis of the target echo is difficult for classical high resolution sonars as they are susceptible to speckle noise and in general not resolved enough for classification. Detection and classification in such challenging scenarios can be improved by detectiing the targets as an outlier in the current texture field. This can be done using 2D or 3D texture measures but as most strong textures are due to the 3D nature of the seabed, we believe that 3D texture analysis will be more effective and therefore propose to focus on these. Classification can be addressed with the development of new higher resolution sonars (SAS) and new 3D sonars (Interferometric SAS / Side Scan). As resolution increases, the structure of the echo will become more apparent and techniques developed in the machine vision and pattern recognition communities can be used. This is the secondary objective of this proposal.