Echo Averaging - Furuno FR-1710 Operator's Manual

Note: The display is automatically shifted by
75% of the range in use whenever the cur-
sor is placed at an edge of the effective dis-
play area.

1.24 Echo Averaging

The echo average feature effectively sup-
presses sea clutter. Echoes received from
stable targets such as ships appear on the
screen at almost the same position every ro-
tation of the scanner. On the other hand, un-
stable echoes such as sea clutter appear at
random positions.
To distinguish real target echoes from sea
clutter, echo average performs scan-to-scan
correlation. Correlation is made by storing
and averaging echo signals over successive
picture frames. If an echo is solid and stable,
it is presented in its normal intensity. Sea clut-
ter is averaged over successive scans result-
ing in the reduced brilliance, making it easier
to discriminate real targets from sea clutter.
To properly use the echo average function, it
is recommended to first suppress sea clutter
with the A/C SEA control and then do the fol-
lowing:
1. Press the [MENU] key.
2. Press the [5] key twice to select the ECHO
SIG menu.
ECHO SIG
1. TGT COLOR
2. ECHO AVG
3. INT REJ
4. N REJ
5. ENHANCE
6. 2ND ECHO
7. CONTRAST
8. CLTR SWEEP
9. SWEEP LVL
0. CNTR ENHANCE OFF ON
Figure 1-23 ECHO SIG menu
1-18
YEL GRN COLOR
OFF 0.5 1 2 3
OFF 1 2 3
OFF ON
OFF ON
OFF ON
1 2 3
OFF ON(LINK) ON(FIX)
1 2 3
3. Press the [2] key to select echo averag-
ing level (OFF, 0.5 1, 2, 3) from the ECHO
AVG field.
OFF: No averaging effect
0.5: Distinguishes small targets from
sea clutter.
1: Distinguishes targets from sea
clutter and suppresses brilliance
of unstable echoes.
2: Distinguishes small stationary
targets such as navigation buoys.
3: Stably displays distant targets.
4. Press the [ENTER/SELECT] key to con-
clude your selection followed by the
[MENU] key to close the menu.
(a) Echo average OFF
Figure 1-24 Echo averaging
Echo averaging uses scan-to-scan signal cor-
relation 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 average is not
however effective for picking up small targets
running at high speeds over the ground.
Echo average requires log and compass sig-
nals. If you wish to use this feature without a
compass signal, consult a FURUNO repre-
sentative.
Manual speed entry is done at the menu item
MAN SPD on the OTHER menu, which is ac-
cessed by pressing the [MENU] and [0]
(twice) keys.
(b) Echo average ON