Furuno color video plotter GD1720C - Manual (Page 132)

4. VIDEO SOUNDER OPERATION
4-3
frequency is useful for general detection and judging bottom condition.
HF picture
The higher the frequency of the ultrasonic pulse the better the resolution. Therefore, the
high frequency is ideal for detailed observation of fish school.
low frequency
high frequency
Sounding area and transmission frequency
Marker-zoom display
The marker-zoom display expands a selected area of the normal sounder picture to full
vertical size of the screen on the left-half window. You may specify the portion to expand by
operating the VRM (Variable Range Marker), which you can shift with the ENTER knob.
The area between the VRM and zoom marker is expanded. The length of the segment is
equal to one division of the depth scale.
Note:
The VRM is set independently from other displays in case of multiple displays.
HF
80
42.0
MARKER-ZOOM
DISPLAY
Fish school
Fish
school
This part
is zoomed.
Zoom marker
VRM
(White on color model)
NORMAL
DISPLAY
50
0
100
-
-
-
-
-
-
-
-
-
-
-
42
44
46
48
50
-
-
-
-
- 0'20"
Marker-zoom display plus normal sounder display