Bottom Lock - Raymarine C140w User Reference Handbook

The standard fishfinder display shows a historical record of fishfinder
echoes. If required, you can display a live image of the bottom
structure and the fish directly below the transducer by using the
A-Scope feature. The width of the bottom covered by the A-Scope
is indicated at the bottom of the window. A-Scope provides a more
precise and easier to interpret indication of the target strength.
There are three A-Scope modes, as illustrated in the diagram below:
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Enabling the Fishfinder A-Scope Mode
From the fishfinder main screen:
1. Press the appropriate ADJUST... softkey.
2. For dual frequency screens, select FREQ1 or FREQ2 to select
which frequency display you wish to change.
3. Press the SELECT VIEW softkey.
4. Use the trackpad up/down to select A-SCOPE.
5. Press OK when complete.
Note: Enabling A-Scope mode automatically switches OFF
Bottom Lock and Zoom.

Bottom Lock

The Bottom Lock function applies a filter to flatten the image of the
seabed and make any objects on or just above it easier to discern.
This feature is particularly useful for finding fish that feed close to
the bottom.
Bottom Lock is selected for individual fishfinder windows and
can replace or appear alongside the standard fishfinder image.
Adjusting the range of the bottom lock image allows you to view
more bottom details. You can also reposition the image on screen to
anywhere between the bottom of the window (0%) and the middle of
the window (50%) by using the Bottom Shift control.
C-Series Widescreen user reference