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Chapter 11: Working with sonar 101
11.10 Measuring an object’s depth and distance
You can use the Variable Range Marker (VRM) t o determine the depth and
distance- behind-the boat of an object on the display. The VRM function
can be used on the scrolling bottom image, bottom lock and zoom pages.
The VRM is displayed as a cross hair with the height and width of the
display screen. The centre of the crosshair is the reference for which depth
Depth
Distance-behind-boat
VRM/EBL
D7018_1
102 RayTech RNS V6.0 - Users Guide
and distance-behind-boat are displayed. You can use the cursor to move
the VRM over a particular object.
Depth is displayed, in system units, on the VRM. In the scrolling bottom
and zoom pages, depth is measured from the surface down. In the bottom
lock page, depth is measured from the bottom up.
Distance-behind-boat is displayed next to the vertical line at the top of the
screen. Depth is displayed above the horizontal line at the left of the
screen.
The distance-behind- boat continues to update as your boat moves.
However, the vertical line does not scroll with the scrolling bottom image.
If the display range changes, the VRM maintains the same position and
may, therefore, move out of the visible display area. When you switch on
the VRM, it is displayed at its last position, unless this is off-screen. If its
last used position is off-screen, it will be displayed in the default on-screen
position.
If you use the VRM with the sonar in split frequency or zoom modes, it will
appear in both panes.
To use the VRM:
1. Click
Presentation
.
2. Click
VRM/EBL
to ON. The crosshair will appear on screen as dashed lines.
3. Click
Edit VRM/EBL
.
4. Use the cursor to move the VRM/EBL to the required position, the depth and
distance will update as you move it.
5. When the VRM/EBL is in the required position, click. The crosshair will remain
in the selected position and change to solid lines. The depth will remain
constant, but the distance-behind-boat will continue to update as the
image scrolls.
11.11 Sonar alarms
You can set up alarms to warn you of:
•Shallow water.
•Deep water.
•Fish.
Each alarm can be turned on and off as required.
Shallow water alarm
The shallow water alarm can be set at any depth between 2ft (0.5 fathoms/
1 meter) and 3000ft (500 fathoms/1000 meters). You set the depth at
which the alarm triggers. When the depth is less than that set, an audible
alarm sounds and a pop-up message describing the alarm is displayed. You
cannot set the shallow alarm to a depth greater than the deep alarm. To
cancel the alarm, click any button.
Deep water alarm
The deep water alarm can be set at any depth between 2ft (0.5 fathoms/1
meter) and 3000ft (500 fathoms/1000 meters). You set the depth at which
the alarm triggers. When the depth is less than that set, an audible alarm
sounds and a pop-up message describing the alarm is displayed. You
cannot set the deep alarm to a depth shallower than the shallow alarm. To
cancel the alarm, click any button.
Fish alarm
If this alarm is on, an audible warning is sounded whenever the sonar
detects a fish. To cancel the alarm, click any button.