Multibeam sonar calibration: removal of static surface reverberation by coherent echo subtraction

Calibration of multibeam sonar in confined environments may require treatment of surface reverberation. In the case of tanks, the method of coherent echo subtraction may be employed to remove static surface reverberation, allowing the tanks to be used for standard-target calibration. This is illustrated for the Simrad SM2000 Multibeam Echo Sounder operating at 200 kHz. The signal-to-noise ratio is typically improved by about 25 dB.