Furuno 1833C Manuel D’Utilisation

4. VIDEO SOUNDER OPERATION 
 
 

The zero line (sometimes referred to as the transmission line) represents the 
transducer’s position, and moves off the screen when a deep phased range is 
used. 

Zero line

Shift

 

Echoes from the bottom are normally the strongest and are displayed in 
reddish-brown, but the color and width will vary with bottom composition, water 
depth, frequency, sensitivity, etc. 
 
In a comparatively shallow depth, a high gain setting will cause a second or 
sometimes a third or a fourth echo to be displayed at the same interval between 
them below the first echo trace. This is because the echo travels between the 
bottom and the surface twice or more in shallow depths. 
 
The color of the bottom echo can be used to help determine the density of the 
bottom materials (soft or hard). The harder the bottom, the wider the trace. If the 
gain is set to show only a single bottom echo on mud, a rocky bottom will show a 
second or third bottom return. The range should be chosen so the first and 
second bottom echoes are displayed when bottom hardness is being 
determined. 

Intensity difference
in water depth

Second bottom
echo

Rock base

Mud and sand