Furuno FR-7112 - Manual (Page 20)

2-8
6.0 NM
2.0
EBL1 bearing
EBL1 bearing 40.0° R
135.0° R
EBL
EBL1
EBL2
Target
Cursor
Cursor
Bearing
40.0°R 4.0 NM
Figure 2-10 How to measure bearing by EBL
and cursor
Note: The bearing readout for the EBL and
the cursor can be displayed in relative
or true bearing (true bearing requires
heading sensor input). For North-up
and Course-up display modes the
bearing reference is always true.
Tips for measuring bearing
¡ Bearing measurements of smaller targets are
more accurate; the center of larger target pips
is not as easily identified.
¡ Bearings of stationary or slower moving tar-
gets are more accurate than bearings of faster
moving targets.
¡ To minimize bearing errors keep echoes in
the outer half of the picture by changing the
range scale; angular difference becomes dif-
ficult to resolve as a target approaches the
center of the display.
2.16 Using the Offset EBL
The offset EBL provides two functions: predict
collision course of radar target and measure the
range and the bearing between two targets.
Predicting collision course
1. Operate the trackball to place the cursor on
the center of the target.
2. Press the [EBL 1] key to turn on EBL1.
3. Press the [EBL OFFSET] key. EBL1’s ori-
gin shifts to cursor location.
4. After waiting several minutes, press the
[EBL 1] key again.
5. Operate the trackball to pass EBL1 through
the center of the target.
If the target tracks along the EBL towards the
center of the display (your vessel’s position),
the target may be on a collision course.
To cancel the offset EBL, press the [EBL OFF-
SET] key.
Offset EBL
(EBL1)
6.0 NM
2.0
EBL1 origin
(initial position
of target)
Target moved
here.
EBL1
bearing
70.0° R
VRM
6.0 NM VRM1
range
EBL
Figure 2-11 Predicting collision course by
using the offset EBL
Measuring range and bearing between
two targets
The procedure which follows shows how to
measure the range and bearing between target
“A” and target “B” in Figure 2-12.
1. Operate the trackball to place the cursor on
the center of target “A”.
2. Press the [EBL 1] key to turn on EBL1.
3. Press the [EBL OFFSET] key. EBL1’s ori-
gin shifts to cursor location.
4. Press the [EBL 1] key.
5. Operate the trackball to bisect target “B” with
EBL1. Check the EBL1 readout to find the
bearing between target “A” and target “B”.
6. Press the [VRM 1] key to turn on VRM1.
Operate the trackball to place the outside
edge of VRM1 on the inside edge of target
“B”. Check the VRM readout to find the
range between target “A” and target “B”.