Acoustic imaging of surface ship wakes

Techniques for three-dimensional visualization of a surface ship bubbly wake using a high-frequency narrow beam profiling sonar are reported. Instrumentation, experimental set-up, and data processing are described. An Imagenex profiling sonar is mounted on the side of a boat at about 1 m below the water surface. The narrow pencil beam scans the water through the sectors whose plane is perpendicular to the direction of the boat motion. Two scanning techniques were used. In the first, the wake is scanned from the side with about 50° sectors, with the profiling boat moving slowly along the wake in the direction opposite to that of wake laying ship. In the second technique the boat moves inside the wake and scans it with a 180° sector. Both techniques have their advantages and disadvantages which are discussed in the paper. The GPS coordinates of the profiling boat and angular position of the sonar head are recorded. These data allow building a three-dimensional image of the bubbly wake during post-processing.