Underwater acoustic applications

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Due to their low absorption in water, acoustic waves are frequently used for remote sensing of various oceanographic variables, bottom sediment classification, ocean bathymetry, fish stock assessment, underwater acoustic communication, navigation and positioning. Most of these applications require good understanding of underwater acoustic channels and sophisticated algorithms for signal compression, transmission and reception. Acoustic transmissions in highly reverberant, time-varying underwater channels often require an adaptive receiver combined with adaptive acoustic beam forming and tracking. This is particularly relevant in shallow water transmissions. Efficient acoustic ray tracing algorithms are needed for precise acoustic navigation and multi-beam acoustic bathymetry. The large amounts of data associated with acoustic sensing require efficient compression for transmission or storage. Any practical design of acoustic sensing systems must address these problems. The proposed research will recognize all these problems but it will concentrate on novel acoustic methods for precise navigation and positioning of underwater platforms such as bottom crawlers and various underwater vehicles. Such platforms are more and more frequently used for ocean research, bottom inspection and in ocean observing system such as planned by Neptune Canada program and several others. New methods for transmission and signal processing will be developed to achieve precisions not attainable by presently available systems. Specific applications to be addressed include also measurements of plate movements where required precision is in order of millimeters over distances in order of kilometers. Achieving such an extraordinary accuracy require new approaches to such measurements. Another area of research will concentrate on new methods for bottom characterization and classification using depth sounders and side-looking sonars. The mapping of bottom type and its topography is important for fisheries, fish stock assessment and other area of ocean exploration.