Seafloor Mapping

Phase-measuring sidescan sonar. Image showing bathymetry (submarine topography) overlaying backscatter imagery. Without bathymetric data this could have been misinterpreted as eelgrass growing northeastward into featureless seafloor. Eelgrass bed is being buried by southwestward migrating sand sheet.

Phase-measuring sidescan sonar. Image showing bathymetry (submarine topography) overlaying backscatter imagery. Without bathymetric data this could have been misinterpreted as eelgrass growing northeastward into featureless seafloor. Eelgrass bed is being buried by southwestward migrating sand sheet.

The Seafloor Mapping Program uses state-of-the-art acoustic instruments to conduct vessel-based shallow water surveys. A bow-mounted, dual frequency phase-measuring sidescan sonar collects coincident bathymetry (540 kHz) and acoustic backscatter imagery (540 kHz, 1600 kHz).

This allows investigators to conduct scientific research, map benthic habitats and locate marine debris, in nearshore, shallow water settings.

The Center also uses a traditional towed sidescan sonar, which also has dual frequencies (600/1600 kHz). This instrument is very useful as it operates at high-frequencies and because it is towed can be used onboard any vessel of opportunity. Recently it was used onboard several lobster boats to locate, identify and retrieve derelict fishing gear.

 

Dual-Frequency Sidescan Sonar. The above images show the starboard channel of the same stretch of seafloor collected at 600 kHz (left) and 1600 kHz (right). Note the different bottom types in the higher frequency.

Dual-Frequency Sidescan Sonar. The above images show the starboard channel of the same stretch of seafloor collected at 600 kHz (left) and 1600 kHz (right). Note the different bottom types in the higher frequency.