Furuno GP-1670F Operator's Manual page 100

7. FISH FINDER OPERATIONS
Size of a school of fish
Usually the size of fish echoes on the screen is proportional to the actual size of the
school of fish. However, if two fish echoes appear at different depths with the same
size, the school of fish at the shallower depth is displayed smaller because the ultra-
sonic beam widens as it propagates and a school of fish in deep water is displayed
larger.
Density of a school of fish
If two 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 school of
fish in deep water tends to be displayed in a weaker color.
Less reddish
(Sparse echo)
Bottom fish
The echoes from the bottom are stronger than
the bottom fish echoes so that you can distin-
guish between them by colors. The bottom ech-
oes are normally shown in reddish-brown or red,
the bottom fish echoes in weaker color.
7-24
School depth and sounding time
Sounding time for a shallow school of fish Sounding time for a shallow school of fish
Sounding time S Sounding time for a deep school of fish g e for e for a deep
Reddish
(Dense echo)
Fish echoes at
the same depth
p school o
Difference in signal strength
Strong echo
Weak echo ak echo o
Bottom fish echo