2019_programme: AN EVALUATION OF METRICS USED FOR SEDIMENT CLASSIFICATION USING NORMAL-INCIDENCE ECHO SOUNDING

• Session: 12. Marine sediment acoustics
  Organiser(s): Ballard Megan , Lee Kevin
• Lecture: AN EVALUATION OF METRICS USED FOR SEDIMENT CLASSIFICATION USING NORMAL-INCIDENCE ECHO SOUNDING [invited]
  Paper ID: 953
  Author(s): Isakson Marcia
  Presenter: Gunderson Aaron
  Presentation type: oral
  Abstract: Different types of underwater water sediments (mud, clay, sand, rock) not only have vastly different mechanical properties affecting underwater engineering, they also have different acoustic properties affecting propagation and scattering. Maps of sediment type are essential for acoustic propagation models especially in shallow water areas where there are many interactions with the ocean bottom. However, assessing sediment type is challenging, often requiring coring or grab samples, which are labor intensive and sparse. Normal-incidence echo sounding provides a method for assessing sediment type quickly and remotely. These measurements are often analyzed with statistical methods using the moments of the return such as mean, variance and skew over a particular time window and frequency bin. The moments can be loosely tied to physical attributes such as amplitude, time spread and late arriving scattering components. These data are then analyzed with principal components and spatially separated using k-means clustering. In this study, a different set of metrics is proposed in which physical attributes are assessed based on the structure of the return including peak height, Full Width and Half Max, and the ratio of the Half Width at Half Max before and after the peak. Both approaches were considered for a set of data from a well-characterized shallow water, sandy environment at the Target and Reverberation Experiment (TREX) conducted off the Florida panhandle in May of 2013. It was found that the physical metrics were less correlated. The study also included a finite-element model of the experiment; the results of which were analyzed using the same metrics. The finite element model was useful in assessing the relative impact of different physical properties such as bathymetry, roughness and gradients. It was found that only the peak height metric was sensitive to these environmental factors. [Work supported by the Office of Naval Research, Ocean Acoustics.]
• Corresponding author: Dr Isakson Marcia
  Affiliation: Applied Research Laboratories, The University of Texas at Austin
  Country: United States
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