Ground-Truthing Side-Scan Sonar Mosaics

This study explored the relationship between bottom sample characteristics and backscatter intensities of high-frequency side scan sonar. Bottom samples collected during the summer of 2009 from an area at the mouth of the Chesapeake Bay in Virginia were compared with side-scan sonar readings taken from the same area by the NOAA hydrographic research ship Thomas Jefferson from 2007-2009. Fifty sediment samples were collected in the study area and analyzed to determine percent carbonate, total organic content, and grain size. These data were then plotted against seven overlapping 455 kHz side-scan sonar mosaics using ArcGIS to visually examine how differences in sediment characteristics relate to differences in the backscatter intensity. Analysis of the data showed that there is a positive correlation between sediment grain size and side-scan backscatter intensity throughout the range of intensities, with a stronger correlation for high intensity areas and coarse grain sizes, but a much weaker correlation in lower intensity areas.