This model further shows potential for statistical impact when multipath arrivals are of similar level as the direct path even when not observable in the image (e.g., within 10 dB). A model for reverberation is presented to provide bounds of the statistical impact using observable image intensity level increases in synthetic-aperture-formed images caused by multipath contamination. Analysis showed a clear and significant increase in the estimated shape parameter in the presence of multipath, representing a trend toward a Rayleigh-distributed envelope. High-resolution sonar imagery often exhibited significantly non-Rayleigh, heavy-tailed envelope statistics, characterized by a low equivalent K-distribution shape parameter. Analysis focused on both system structure and environmentally induced multipath using the K -distribution shape parameter as a metric. Office of Naval Research (ONR)-funded Sediment Acoustics eXperiment 2004 (SAX04) are analyzed in this paper. The software has undergone a few revisions where bug fixes were made and additional features were added. GPLAB was developed by Sara Silva while doing her PhD at the University of Coimbra in Portugal. Broadband acoustic data suitable for SAS processing collected with a rail-mounted mobile-tower as part of the U.S. GPLab is a Genetic Programming toolbox specially developed for MATLAB. A clear understanding of such statistical impact is necessary to advance synthetic aperture formation algorithms and for predicting system performance. Such multipath contaminants may either be environmentally induced, as is often the case when attempting to image ranges greater than the water depth resulting in returns from the boundaries, or may be induced by the system's supporting structure itself. As with traditional sonar, synthetic aperture sonar (SAS) is susceptible to multipath contamination, reducing the quality and also modifying the statistics of the image.
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