DATA ACQUISITION – SIDE-SCAN SONAR
Acoustic backscatter data were collected with a Klein 3900 side-scan sonar towfish flown off the port quarter of the USGS research vessel RV G.K. Gilbert (fig. 3) approximately 3–4 m astern. Klein SonarPro acquisition software (Klein Associates, Inc.) was used to aquire the side-scan data and manage cable out and layback offsets. Horizontal offset values between the side-scan towfish and DGPS antenna were entered into SonarPro, which calculated fish position dynamically during acquisition. The towfish itself has internal sensors for attitude, including a gyroscope for independent heading. The Klein 3900 instrument is a dual frequency sonar (445 kHz and 900 kHz). Data were processed at the lower frequency to maximize swath width in shallow water. The data files were recorded as Extended Triton Format (XTF) files along the common navigation survey tracklines shared by the other geophysical instrumentation deployed in this survey. Approximately 487 line-km of data were collected along 76 tracklines spaced over 300 m apart.
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Table 7. Specifications for the Klein 3900 side-scan sonar towfish used to collect acoustic imagery of the seafloor (http://www.l-3klein.com/3000series/3000specs.html).
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