Target-tracking with a multiple-frequency split-beam echo sounder

During a calibration trial with the Kongsberg TOPAS PS18 sub-bottom profiling parametric sonar, the Simrad EK60 split-beam scientific echo sounder was used to track the position of a standard target in the TOPAS beam. The target was a 280-mm-diameter solid sphere composed of the aluminum alloy 6082 T6. Simultaneous measurements were performed with proximate transducers operating at 18, 38, 70, 120, 200, and 333 kHz. The beamwidths were 7 deg at all frequencies except at 18 kHz, where the beamwidth was 11 deg. The target range was about 90 m. Position data are compared ping-by-ping relative to the individual transducers and in a common reference frame defined by the vessel motion reference unit and sea surface.