Topic summary
Echosounder

Extracted from the Wikipedia article Echo sounding.
Hydrography
A multispectral multibeam echosounder is an extension of a dual frequency vertical beam echosounder in that, as well as measuring two soundings directly below the sonar at two different frequencies; it measures multiple soundings at multiple frequencies, at multiple different grazing angles, and multiple different locations on the seabed. These systems are detailed further in the section called multibeam echosounder.