Bottom detection methods in single beam echo sounding (SBES) are often less robust in areas with subaquatic vegetation. Due to current mapping efforts emphasizing near shore coverage for safety of navigation and the mission for alternative uses of hydrographic quality data with the Integrated Ocean and Coastal Mapping (IOCM) Center, there is a requirement for both robust bottom detection in areas with complex vegetation and delineation of the vegetated areas themselves. Vegetation can often be found growing in close proximity to rocks and other features of navigational significance and would provide valuable information to fisheries if prime fish habitats like eelgrass could also be mapped with the navigational hazards. A bottom detection algorithm implemented in the program TracEd is being evaluated for handling bottom detections on eelgrass in the water column. This algorithm allows for detections of multiple returns in a full waveform trace for each ping. Each of these returns is then tagged as being associated to seafloor or water column features. Should this algorithm prove to be more robust in recognizing returns from vegetation and identifying the underlying bottom, a systematic approach for NOAA to more accurately determine depth in areas of sub-aquatic vegetation might be possible. A full waveform SBES dataset collected in New Hampshire’s Great Bay Estuary is under analysis to determine whether bare earth can be distinguished from the eelgrass canopy in this area where eelgrass is common and well studied. Additionally, characteristics of the waveform necessary for bottom detection are also being evaluated for eelgrass mapping.
Journal or Conference Title
U.S. Hydrographic Conference
Apr 25 - Apr 28, 2011
Tampa, FL, USA
Hydrographic Society of America
T. Beduhn and S. Dijkstra, "On the horizon: Better bottom detection for areas of sub-aquatic vegetation," in US Hydro, 2011. [Online]. Available: http://ushydro.thsoa.org/hy11/0427A_03.pdf.