Development to high‐resolution side‐look sonar

Abstract

About 28 years ago, the Navy had a requirement to scan the bottom of channels and harbors with sufficient resolving power to identify minelike objects on the bottom with cylindrical dimensions 112 in. in diameter by 6 in. long. A side‐scan sonar was designed to provide a narrow fan shaped beam focused on a line on the bottom by means of a fixed arc array. The transducer array had to be towed a fixed distance (the radius of curvature of the arc array) off of the bottom for optimum focus. The system scanned the bottom by means of the vehicle movement in the direction of tow and perpendicular to the direction of tow by the travel time of the acoustic signal emitted from the transducer to the bottom. This system had a number of limitations: bottom coverage rate (m2/h), fixed height above the bottom, a limited display capability, and limited signal processing. These led to the development of multibeam arrays with electronic all‐range focusing, CRT displays, and adaptive time varied gain tied into the background reverberation levels.