Digital sediment charts (DSC) using multibeam sonar data

Waterway and ocean bottom sediment maps have traditionally been created using core samples and grab samples. Limited data is available from single beam sonars which have the ability to classify the bottom sediment after some pre-tuning. Core, grab and single beam sonar samples all suffer from the fact that only sparse sediment samples are available for bottom mapping. A new high resolution source of data has recently become available using amplitude from multibeam sonars. Multibeam sonars provide up to 4000 bottom samples in the athwart ship direction. These samples are traditionally used to map a swath of the bottom with respect to depth. A new Multibeam Bottom Sediment Classification Algorithm (MBSCA), scheduled for installation on the new Pathfinder TAGS-60 survey vessel, uses sonar amplitude to determine the bottom sediment type. The classification algorithm relies on a one-time transducer and hydrophone calibration at initial sonar installation in dB/uPa. Because amplitude is calibrated, no at sea tuning is needed. The MBSCA algorithm was developed using data collected on the Tags-34 USNS Wyman survey vessel. Surveys were conducted in areas with known core sample data. This paper compares sediment data derived from USNS Wyman multibeam sonar returns to core sample measurement data "ground truth".