Acoustic Wavefront Distortion and Compensation
2006
Waag, Robert C.
Ocean propagation models were reviewed and a ray tracing model was selected for use this research. An ray tracing program, TRIMAIN, was obtained and adapted to calculated time delay differences due to sound speed variation with depth in the ocean. An imaging algorithm was also obtained and adapted to include time delay distortion and employ data covering a finite aperture with sparse sampling. Specially modified source code was documented and transferred to the Naval Research Laboratory. Maximum brightness, cross correlation, and triple correlation techniques for the compensation of wavefront distortion were studied and an overview with references was prepared. The propagation model and imaging algorithm were used with available measured scattering data to find image degradation produced by various combinations of sound speed profile, measurement aperture size, and spatial sampling rate. The results indicate little degradation occurs when the spatial aperture is limited by the reliable acoustic path and that image characteristics may still be recognized when the spatial sampling rate is significantly reduced.
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