Fig. 1
From: Acoustic water bottom investigation with a remotely operated watercraft survey system
Sonar images obtained by a a 200 kHz acoustic source (P391 transducer, Airmar), b 455 kHz acoustic source (StructureScan® HD, Lowrance), and c 455 kHz side-scan (StructureScan® HD, Lowrance) for the same track. The red arrows indicate the submerged trees; X and Y on a and b are the same objects. Brighter images suggest stronger acoustic reflection. c Side-scan image shows the areal distribution of acoustic reflections on the lake floor; prominent materials on the floor are bright and their shadows are dark. Thus, the shape of materials on the floor is identifiable; for example, submerged trees (yellow arrows) have long shadows