SIDESCAN SONAR

Imaging the sea floor with a sidescan-sonar system is accomplished by towing a sonar “tow-fish” over the study area. The tow-fish is equipped with a linear array of transducers that emit, and later receive, an acoustic energy pulse in a specific frequency range. The acoustic pulse is specifically designed such that it is wide in the across-track direction, and narrow in the along-track direction. The acoustic energy (backscatter) received by the sidescan-sonar tow vehicle provides general distribution and characteristics of the surficial sediment and outcropping strata. In general, if all other parameters are constant, a rougher surface will backscatter more energy than a smooth surface and therefore, return higher amplitude signals. Shadows result from areas of no energy return, such as shadows from large boulders or sunken ships, and aid in interpretation of the sonogram (after Urick, 1983; Fish and Carr, 1991).