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GPSMAP 198C 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—shows only the Bottom Lock picture
(returns from the bottom up) on the full screen. However, if
Dual Frequency Screen is set to Split, then a 50/200kHz split
screen shows.
When started, the zoomed picture becomes the Sonar Page. You
can also cycle through the sonar zoom levels by pressing the IN
or OUT keys. The Zoom function can be stopped 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
screen. 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 shows 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 screen.
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
screen.
Target Level
—adjusts how dark or light a return
(or target) is shown 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.
Gain Adjustment
Target Level
Selection
View
Adjustment