Single (left) and multibeam (right) echo sounding of the seafloor. Single beam systems typically have beam widths of 10-30 degrees and estimate depth by measuring the shortest slant range to the seafloor within the main beam. Multibeam (swath sonar) systems provide a series of slant range and elevation angle estimates along a fixed azimuth. This method is preferred since it measures an entire area rather than a single line of seafloor. Image courtesy of Lewis and Clark 2001, NOAA/OER.