Assessment of the operational resolving power of small imaging sonars

Several small commercial imaging sonars were tested to determine the actual resolving power of the systems. Experiments were performed with specially designed resolution targets in a large tow tank facility at the National Research Council Institute for Ocean Technology, with precise control of sensor-target geometry, and in the Defence Research & Development Canada calibration tank. Resolving power has been assessed for several high frequency imaging sonars (450 to 1800 kHz) using an analog to resolving criteria as defined for optical systems. Small imaging sonars are a sensor of choice for underwater inspection tasks using Remotely Operated Vehicles, particularly in the not-uncommon situation that water clarity limits the usefulness of video. Sonar manufacturers´ specifications do not usually provide a complete picture of the ability of any particular system to perform in this role.