An experimental synthetic aperture SONAR

Aperture synthesis is a mature technique that has been used with success in a number of remote sensing fields. Sonars can also potentially benefit from the technique, though to date the limitations of slow acoustic propagation and difficulty in maintaining a stable platform has hindered investigation. This thesis investigates aperture synthesis for high resolution underwater imaging. A prototype sonar is designed and fabricated for the study. The performance of the sonar is assessed in both tank and sea trials and the results presented in this thesis

Advances in Sonar Technology

The demand to explore the largest and also one of the richest parts of our planet, the advances in signal processing promoted by an exponential growth in computation power and a thorough study of sound propagation in the underwater realm, have lead to remarkable advances in sonar technology in the last years.The work on hand is a sum of knowledge of several authors who contributed in various aspects of sonar technology. This book intends to give a broad overview of the advances in sonar technology of the last years that resulted from the research effort of the authors in both sonar systems and their applications. It is intended for scientist and engineers from a variety of backgrounds and even those that never had contact with sonar technology before will find an easy introduction with the topics and principles exposed here

Interferometric synthetic aperture sonar system supported by satellite

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

A new algorithm for high-precision submarine topography imaging

730-738In this paper, a new algorithm for high-precision submarine topography imaging is proposed. The innovative idea comes from the most effective and widely used instruments: Multibeam echo sounder (MBES) and side scan sonar (SSS). The MBES can acquire bathymetric information with high precision, but its along-track resolution is related to the result of the beam angle multiplied by the slant range. The SSS combined with synthetic aperture sonar technology can achieve a high-precision along-track imaging resolution, but it cannot acquire bathymetric information directly below it. The proposed algorithm uses the beam footprints of the MBES in the along-track direction to perform the aperture synthesis and uses the time-domain and beam-domain imaging algorithms to acquire high-precision along-track imaging resolution and bathymetric information, to improve the along-track resolution and obtain the bathymetric information with high precision at the same time. Finally, an experiment is performed to evaluate the effectiveness of our method. Experimental results demonstrate that two targets, 13 cm in size, can be clearly observed from the obtained imaging. Moreover, their bathymetric information can be calculated by using the beamforming angle information

Synthetic Aperture Techniques for Sonar Systems

Today a good percentage of our planet is known and well mapped. Synthetic aperture techniques used in space and airborne systems has greatly aided to obtain this information. Nevertheless our planet is mostly covered by water and the level of detail of knowledge about this segment is still very far away from that of the land segment

Synthetic aperture sonar

Synthetic aperture techniques have been applied very successfully for many years in astronomy and radar to obtain high resolution images, an outstanding example in recent years being the use in remote sensing satellite systems. In underwater acoustics, because of the inherent problems caused by random fluctuations in the signal path, the slow velocity of the acoustic wave and the unknown movements of the transducer as it traverses the aperture, the application of the synthetic aperture technique has mainly been limited to the very useful but rather inferior non-coherent technique known as side-scan sonar. However the rapid advances that are being made in micro-chip technology and fast digital signal processing, and the development in image processing algorithms has created renewed interest in the possible application of the synthetic aperture technique to underwater acoustics. This thesis describes such a study

Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating Shallow Water

The goal of the research was to develop best practices for image signal processing method for InSAS systems for bathymetric height determination. Improvements over existing techniques comes from the fusion of Chirp-Scaling a phase preserving beamforming techniques to form a SAS image, an interferometric Vernier method to unwrap the phase; and confirming the direction of arrival with the MUltiple SIgnal Channel (MUSIC) estimation technique. The fusion of Chirp-Scaling, Vernier, and MUSIC lead to the stability in the bathymetric height measurement, and improvements in resolution. This method is computationally faster, and used less memory then existing techniques