NorthStar Navigation EXPLORER 435 - Manual (Page 19)

Northstar Explorer 435/438 Installation and Operation Manual 19
Note: Times indicated are for illustration only.
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Stationary boat
When a boat is stationary, all bottom echoes will come from the same
small area of bottom. This will produce a flat bottom trace on the
screen.
The appearance of the Sonar and Zoom screens can be
changed to suit individual preferences.
4-2 Fish detection and display
Where to find fish
Underwater features like reefs, wrecks and rocky
outcrops attract fish. Use the sonar to find these
features, then look for fish by passing over the
feature slowly several times using the Zoom
display (see section 5-2 Sonar Zoom display). If
there is a current, the fish will often be found
downstream of the feature.
When fishing with the Explorer 435 and Explorer
438 with the Fish symbols Off, a weak fuzzy band
may appear between the bottom trace and
surface. This might indicate a thermocline - a
rapid change in water temperature, such as the
edge of a warm or cold current. The temperature
difference can form a barrier which the fish
may not swim through. In fresh water, fish often
collect around a thermocline.
Fish symbols
The fish symbol can be customized or switched
off altogether so that the echoes are not
converted to fish symbols on the display. See
section 3-2 Setup > Sonar. The differences
between Fish symbol On and Off are:
Fish symbols On
Using Northstar’s SBN sonar technology the
fishfinder analyses all echoes and eliminates most
false signals and clutter so that remaining targets
are most likely fish. Depending on the strength of
the remaining
echoes,
they are
displayed as
either small,
medium or
large fish
symbols
- with or
without
depth. While
the SBN
processing
is very
sophisticated
it is not
foolproof - there will be times when the fishfinder
will not be able to differentiate between large
air bubbles, rubbish containing air, fishing floats
etc. and fish.
The following picture shows the Sonar display with
the Fish symbol: On + depth:
Fish symbol Off
For experienced users this always provides the
best information as every echo is displayed,
whether it is surface clutter, a thermocline or a
fish.
The picture in section 4-1 Interpreting the display,
shows the Sonar display with the Fish symbols
Off. The fish appear as arches.