The use of a side looking echo sounder to determine the profile of an ice ridge

In the Baltic experiments were made using an echo sounder with the transducer rotated around a horizontal axis at the end of an 8 to 14 meter aluminum tube. Each turn gave a visible record of the profile. Using a narrow beam (0.7/deg) the selectivity was good even from a long distance. From a shorter distance echoes were reflected both from the front and from the back side of the first ice floe in the keel and thus the thickness and the width of the ice floe were easily determined. Sometimes several ice floes behind each other gave echoes. Efforts have been made to install the side looking echo sounder on an icebreaker.