Simrad CE33 ChartSounder Manual page 28

Chapter 3-6 CE33 Chart menu and INFO windows
In addition to the larger boundaries of the world chart there will be
separate boundary lines for the individual charts stored on the same
cartridge. However, the boundary lines for the C-MAP chart areas
can be turned off, so they will not be visible on the chart - refer to
section 3.4 Chart setup.
Other chart areas can quickly be reached by means of the zoom keys:
+
Zoom out until desired area becomes visible
Move cursor to approximate area, and...
-
Zoom in
The chart will automatically start to move when cursor reaches the
edge of the screen. When cursor is switched off [CLR], the chart will
return to ship's position.
See also section 3.4 Chart setup.