Onwa KF-667 - Manual (Page 14)

ZOOM mode (high or low frequency)
Three types of zoom displays are available: marker zoom, bottom-lock expansion,
bottom zoom. The zoom mode to be used can be selected on the main menu with ZOOM MODE.
2-3
Zoom marker (yellow)
Normal
display
Bottom-
lock
display
BOTTOM-LOCK
This display provides a compressed normal picture on the
top 2/3 of the screen and a 5 or 10 meter (10 or 20 feet)
wide layer in contact with the bottom is expanded onto the
bottom 1/3 of the screen. This mode is useful for bottom
discrimination. Note that the seabed should be steadily
and distinctly plotted in red or reddish-brown. Adjust the
gain if necessary.
Note1:The bottom-lock range can be selected on the
system menu.
Note2:The zoom marker can be turned on/off on the
system menu.
Bottom-zoom
display
Zoom
marker
(yellow)
Normal
display
BOTTOM ZOOM
This mode expands bottom and bottom fish echoes two to
five times to vertical size of the screen, and it is useful for
determining bottom hardness. A bottom displayed with a
short echo tail usually means it is a soft, sandy bottom. A
long echo tail means a hard bottom.
The zone automatically moves so that the bottom echoes
locate on the lower half of the screen.
Note1:The amount of expansion can be selected on the
system menu.
Note2:The zoom marker can be turned on/off on the
system menu.
Normal
display
This section
is zoomed
Marker-zoom
display Zoom marke
(yellow)
This mode expands selected area of the normal picture to
full vertical size of the screen on the left-half window. You
may specify the portion to expand with the VRM (Variable
Range Marker), which you can shift with [ ]or [ ]. The
area between the VRM and the zoom range marker is
expanded. The length of the segment is equal to one
division of the depth scale.
MARKER ZOOM
Variable range
marker(green)