The precision calibration of depth and resolution for multibeam sonar in anechoic pool in the laboratory

Abstract

The multibeam sonar is an important device for underwater survey, of which the measurement precision is a key parameter. We had designed an equipment to calibrate the depth and resolution precision for multibeam sonar in the anechoic pool in the laboratory. The main frame of the equipment is built up by circular and square steel pipes. The absorption materials are laid outside of the pipes, so that the multibeam sonar cannot receive the strong enough reflected acoustic waves from the boundary. We had made a two-dimensional scanning mechanism, which ascends and descends freely for evaluating the depth precision of multibeam sonar. The minimum precision of the depth is 0.1 mm. We had set up a series of iron blocks with the dimension of 0.1,0.2,0.4,0.6,0.8, and 1.0 square meters, respectively, as the standard objects for evaluating the resolution capability of multibeam sonar. In addition, we had placed an underwater camera system to record the iron blocks in time. The result of iron blocks measured by the calibrated multibeam sonar is compared to that recorded by the camera. Because the wavelength of acoustics is larger than that of optics, therefore, good precision of the resolution can be gotten.