Simrad ES60 - REFERENCE MANUAL REV H Reference Manual page 16

System description
The bottom detection algorithm locks to the first good bottom
return. The depth at point A rather than the depth along the
transducer axis will be output for a sloped bottom. The detected
depth value is always smaller than the depth along the
transducer axis implying that a safety margin is automatically
included.
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857-160970 / Rev.H