The Picture Menu - NorthStar 972 Quickstart Manual And Reference Manual

The picture menu

Reference section 7 — Echo sounding
114

The picture menu

You can adjust the appearance of echoes in
five different ways:
gain (for high intensity echoes)
•
clutter (for low intensity echoes)
•
noise limiter (for interference)
•
hue (to choose colors and white level)
•
signal level (to remove weak echoes)
•
Gain and clutter changes are applied only
to new echoes as they appear on the right
side of the screen — earlier echoes are not
affected.
Adjusting the gain (strong echoes)
The gain setting selects the echo strengths
that will be displayed using the topmost
color in the color bar at the left edge of the
screen (the strongest echoes).
Any echoes stronger than this selection
will use the same color and no detail can
be distinguished. The gain is usually set so
that strong seabed echoes are displayed in
brown, the strongest level.
The gain can be also be set automatically
by pressing Auto. This provides an excel-
lent picture under most conditions, and
allows the sounder to reliably detect the
seabed depth.
Gain is normally adjusted together with
clutter, as described on the next page.
To adjust the gain:
1. At the Echo Sounder screen, press
Gain
2. Press .
3. Press the cursor pad up or down to adjust the
gain, or use the keypad to manually enter the
desired gain value. The available settings
range from zero (minimum) to 75 (maximum).
Return
4. Press to go back to the Echo
Sounder screen.
Adjusting the clutter (weak echoes)
The clutter setting selects the echo strength
that will be displayed using the bottom
colors of the color bar (the weaker echoes).
Any echoes weaker than this selection are
not displayed. If you select a clutter value
of 5, for example, all weak and moderate
echoes are suppressed. You might choose
this setting to eliminate high levels of
background noise and echoes from turbu-
lence or plankton.
A setting of 0 allows all echoes to be
displayed.
To adjust the clutter:
1. At the Echo Sounder screen, press
Picture
.
Picture
.
Northstar 972