Abstract: A method of calibrating a side scan sonar system by allowing the sonar transducer to roll with respect to the plane of a reference surface to be scanned; measuring the roll angle of the transducer during collection of backscattered sonar data; using backscattered sonar data from a range of transducer roll angles and the measured roll angle to decouple the operating characteristics of the transducer from the angular backscatter characteristics of the reference surface; thereby obtaining an estimate of the operating characteristics of the transducer.