Figure 2. Photo of NOAA Ship RUDE (taken by NOAA). Click on figure for larger image.

Sidescan-sonar and multibeam-echosounder bathymetry data were collected in 2004 during survey H11310 aboard the NOAA Ship RUDE (fig. 2). A high-resolution Klein 5500 was used to acquire the sidescan-sonar data, transmitting at 455 KHz and using 5 beams on each side of the ship's track. Shallow water multibeam data were acquired using a Reson 8125, operating at 455 KHz. This system sends 240 beams along a 120 degree swath across the ship's track. Both the sidescan-sonar and multibeam data have 1-meter resolution and were digitally recorded in XTF (extended Triton format) using ISIS data-acquisition software. Data were processed using CARIS HIPS/SIPS software. Sidescan-sonar and multibeam data were converted to geographic coordinates. Sidescan-sonar shading was inverted and enhanced such that light tones indicate strong acoustic reflectivity and coarser grained sediment while dark tones indicate weak acoustic reflectivity and finer grained sediment.

Surficial sediment samples, used to verify the sidescan-sonar data, were previously collected using a Petterson grab sampler and analyzed for grain size (McMaster, 1960). Sediment classifications in this report are based on Shepard's (1954) nomenclature as modified by Schlee (1973).