Imaging and spectral analysis of underwater objects*

Coherent sonar provides a versatile tool for the study of underwater objects and environments. High resolution images of the seafloor may be formed through the use of a synthetic aperture. Scattering from objects on the seafloor may be used to identify their position, orientation, shape, and material properties. Fourier based imaging algorithms are used to isolate objects from nearby clutter, and the acoustic spectra of the objects may be used to aid identification. In the work performed at Washington State University, scaled sonar experiments test new sonar algorithms and examine physical scattering mechanisms. Scattering experiments with canonical targets, such as spheres and cylinders, are carried out and mechanisms including surface elastic waves, internal glory rays, and shape modes are observed. Images of the objects formed using a variety of scan geometries are explored. Finally, a full scale collaborative experiment carried out with the University of Washington is discussed.