Zero Line; Bottom Echoes - Furuno FCV-1200L Operator's Manual

4.2

Zero Line

The zero line represents the transducer's position. It moves off the screen when a shifted range
is used, or is shown at draft depth when ship's draft is entered.
4.3

Bottom Echoes

Bottom echoes are normally strongest and displayed in reddish brown or red, but colors and
width will vary with bottom material, depth, sea condition, installation, frequency, pulselength
and sensitivity.
Bottom profile
A hard and rough bottom appears with a longer tail because it reflects more of the ultrasonic
pulse. Because of their stronger return, shallow echoes appear wider than deep ones even
when all botom conditions are equal. Also, a longer bottom tail appears on slopes because of
the difference in traveling time at both edges of the beam angle. In the rugged bottom, echoes
are reflected on many different planes, overlapping to present a 3D effect.
Color difference
Second bottom
echo
4-2
Range shifted
Zero line
Bottom material and bottom profile
Zero Line
Rugged
bottom