Echo Averaging (Eav 1/2/3) - Furuno FR-2155 Service Manual

2.12 Echo averaging (EAV 1/2/3)

Remarks on the echo-averaging feature
Echo averaging is a useful feature when used properly. If used improperly, however, the
result could be disastrous.
Objective and principle of echo averaging
The main objective of echo averaging is to discriminate targets (flocks of birds, other ships,
fishing floats, etc.) hidden in sea clutter, and stably display long range targets (ship, buoy,
island, etc.) which alternately appear and disappear on the screen.
Normally, unstable echoes such as those from sea clutter and noise appear at random
positions with every rotation of the antenna. To distinguish real target echoes from clutter, the
picture is stored and averaged over successive picture frames. If an echo is solid and stable it
is shown in its actual intensity. Unstable echoes are reduced in intensity.
The following illustrates how echo averaging EAV 1/2/3 work.
OFF
EAV1
EAV2
EAV3
Echo level
15
1 2
Echo level
15
1 2
Echo level
15
1 2
Echo level
15
1 2
Figure 2.8 Echo Averaging
2-13
No. of Scan
No. of Scan
No. of Scan
No. of Scan
FR-2115-SME-27C