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GPSMAP 188/188C Sounder Owner’s Manual 81
USING SONAR > SONAR PAGE
• Btm (Bottom) Split—shows two reduced pictures; the right
at the original depth scale and the left showing sonar returns
from the bottom up. All target depths read as a distance from
the bottom.
• Btm (Bottom) Lock—displays only the Bottom Lock
picture (returns from the bottom up) on the full screen.
However, if Dual Frequency Display is set to Split, then a
50/200kHz split screen appears.
When activated, the zoomed picture becomes the Sonar Page
display. You can also cycle through the sonar zoom display levels
by pressing the IN or OUT keys. The Zoom function can be turned
off by pressing the OUT key until the No Zoom setting appears.
View/Span
—available when a Zoom scale
other than No Zoom is selected. The View or
Span setting is used to change the viewing
range of a zoomed display. If the Zoom is
set to 2X split or 4X split, only the zoomed
portion on the left side of the screen is
affected by the change. If the Zoom is set to
Bottom Split or Bottom Lock, Span adjusts
how far off the bottom the unit displays
data. In Zoom mode, you can control the
view of the left side of the split.
Gain—allows you to control the sensitivity
of the unit’s receiver. This provides some
flexibility in what is seen on the display.
To see more detail, increase the receiver
sensitivity by selecting a higher gain
percentage. If there is too much detail
or if the screen is cluttered, lowering the
sensitivity can increase the clarity of the
display.
Target Level—adjusts how dark or
light a return (or target) is displayed
on-screen. A Color Bar (see page 86)
appears on the right side of the screen
as you adjust this setting. The higher
the percentage, the darker the return
appears. This setting does not increase
or decrease the unit gain.
View Adjustment
Gain Adjustment
Target Level Selection