Furuno GP-3500F User Manual
Page 215
11. VIDEO SOUNDER OPERATION
11-43
If two fish schools appear with the same color at different depths, the one in
deeper water is denser because the ultrasonic wave attenuates as it propagates
and the fish school in deep water tends to be displayed in a weaker color.
Fish Echo
Less Reddish
(Sparse echo)
Reddish
(Dense echo)
Diference in
signal strength
Weak Echo
Strong
Echo
Fish school density
Fish schools at bottom
Because bottom echoes are stronger than fish school echoes, it is possible to
distinguish them by echo color. When the gain is properly set, bottom echoes are
displayed in reddish-brown or red, and fish school echoes in weaker colors.
Bottom
fish school
Other
Plankton
A plankton lager, a likely place to find fish, is displayed in green or blue dots.
Fish School
Plankton
Plankton