Underwater exploration is becoming more and more important for many applications involving physical, biological, geological, archaeological, and industrial issues. This paper aims at surveying the up-to-date advances in acoustic acquisition systems and data processing techniques, especially focusing on three-dimensional (3-D) short-range imaging for scene reconstruction and understanding. In fact, the advent of smarter and more efficient imaging systems has allowed the generation of good quality high-resolution images and the related design of proper techniques for underwater scene understanding. The term acoustic vision is introduced to generally describe all data processing (especially image processing) methods devoted to the interpretation of a scene. Since acoustics is also used for medical applications, a short overview of the related systems for biomedical acoustic image for motion is provided. The final goal of the paper is to establish the state of-the art of the techniques and algorithms for acoustic image generation and processing, providing technical details and results for the most promising techniques, and pointing out the potential capabilities of this technology for underwater scene understanding.

Three-dimensional image generation and processing in underwater acoustic vision

In this paper, an algorithm devoted to the segmentation of acoustic three-dimensional sparse images is presented. The goal is the discrimination and the reconstruction of the objects present in an underwater scene. The final aim is to obtain an augmented representation of such images providing a virtual representation of the recognized objects in order to support a human operator for the navigation and inspection of underwater environments.

Segmentation of underwater 3D acoustical images for augmented and virtual reality applications

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Complete list of publications

Acoustic imaging is an active research field that aims to study techniques for the formation and processing of images generated by raw signals acquired by an acoustic system [1]. Our purpose is to present a brief survey concerning the generation and processing of acoustic images for underwater applications [2,3], especially focusing on algorithms for three-dimensional (3-D) imaging. Like optical systems, acoustic systems can generate an image by processing the waves backscattered from the objects of a scene. The relative ease of measuring the timeof-flight of an acoustic signal makes it possible to generate not only acoustic 2-D images similar to optical ones but also range estimates that can be used to produce a real 3-D map.

Three-dimensional underwater acoustical imaging and processing

In this paper, a system aimed at the augmented representation of underwater scenes is presented. The system operates on three-dimensional acoustic images and is composed of several modules devoted to noise filtering, segmentation in pipe-shaped structures, recognition and reconstruction. Finally, identified objects are backprojected in the acoustic image in order to facilitate its interpretation. The final aim is to obtain an augmented (or virtual) representation of such images providing a useful tool to support a human operator for navigating in and inspecting underwater environments.

Augmented representation of underwater scenes by segmentation and reconstruction of 3D acoustic images

This paper presents a technique for the segmentation of three-dimensional (3D) images acquired by an acoustical camera. The proposed algorithm identifies first the most reliable image points likely corresponding to man-made objects, and, second, determines the points belonging to the same surface. Actually, it exploits the geometrical properties embedded in the sparse and noisy 3D information available to group the points which better fit the current quadric surface. This algorithm can be applied for the reconstruction of virtual environments from acoustic data, useful for robotic applications (e.g., vehicle navigation). Results on synthetic and real acoustic images are promising.

http://ieeexplore.ieee.org/iel4/5877/15668/00725813.pdf

S. Bianchini

Papers

A geometric approach to the segmentation and reconstruction of acoustic three-dimensional data