Furuno FAR-21 7-BB Series, Operator'S Manual

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1. RADAR OPERATION
1-44
1.27 Echo Averaging
The echo averaging feature effectively suppresses sea clutter. Echoes received
from stable targets such as ships appear on the screen at almost the same
position every rotation of the antenna. On the other hand, unstable echoes such
as sea clutter appear at random positions.
To distinguish real target echoes from sea clutter, echoes are averaged over
successive picture frames. If an echo is solid and stable over successive frames,
it is presented in its normal intensity. Sea clutter is averaged over successive
scans and its brilliance reduced, making it easier to discriminate real targets
from sea clutter.
Echo averaging uses scan-to-scan signal correlation technique based on the
true motion over the ground of each target. Thus, small stationary targets such
as buoys will be shown while suppressing random echoes such as sea clutter.
True echo averaging is not however effective for picking up small targets running
at high speeds over the ground.
Note 1: Do not use the echo averaging function under heavy pitching and
rolling; loss of targets can result.
Note 2: Echo averaging can be used without a heading sensor. For further
details, contact your dealer.
Note 3: Echo averaging requires heading, position and speed data.
To properly use the echo averaging function, it is recommended to first suppress
sea clutter with the A/C SEA control. Then, do as follows:
1. Roll the trackball to choose the PICTURE box at the left side of the display.
2. Push the right button to show the PICTURE menu.
3. Roll the wheel to choose 3 ECHO AVERAGE and then push the wheel or the
left button.
4. Roll the wheel to choose OFF, 1, 2 or 3 as appropriate and then push the
wheel or the left button. Chosen setting appears at the top left corner.
OFF: Echo averaging OFF
1, 2:
Detects targets hidden in sea clutter. “2” is more effective than “1” in
detecting targets hidden in strong sea clutter. However, “1” is more
effective than “2” in displaying high speed targets. Choose the
setting best suited to current conditions. For effective monitoring of
high-speed craft, you should use “2” together with Wiper.
3: Stably displays unstable targets; distinguish high-speed craft from
sea
clutter.
5. Push the right button to close the menu.