Furuno FAR-21 7-BB Series, Operator'S Manual

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1. RADAR OPERATION
1-36
1.22 Collision Assessment by Offset EBL
The origin of the EBL can be placed anywhere with the trackball to enable
measurement of range and bearing between any targets. This function is also
useful for assessment of the potential risk of collision. It is possible to read CPA
(Closest Point of Approach) by using a VRM as shown below (Figure (a)). If the
EBL passes through the sweep origin (own ship) as illustrated (Figure (b)), the
target ship is on a collision course.
1.22.1 How to assess risk of collision by the offset EBL
By keyboard
1. Press the [EBL ON] key to display or activate an EBL (No. 1 or No. 2).
2. Place the cursor (+) on a target appearing as threatening (A in the illustrated
example on the next page) by operating the trackball.
3. Press the [EBL OFFSET] key, and the origin of the active EBL shifts to the
cursor position. Press the [EBL OFFSET key] again to anchor the EBL origin.
4. After waiting for a few minutes (at least 3 minutes), operate the EBL rotary
control until the EBL bisects the target at the new position (A'). The EBL
readout shows the target ship's course, which may be true or relative
depending on the EBL bearing reference setting.
Note: If relative motion is selected, it is also possible to read CPA by using a
VRM as shown in left-hand figure at the top of the next page. If the
EBL passes through the sweep origin (own ship) as illustrated in the
right-hand figure at the top of then next page, the target ship is on a
collision course.
5. To return the EBL origin to the own ship's position, press the [EBL OFFSET]
key twice.
By trackball
1. Display an EBL, following steps 1-3 in “By trackball” in paragraph 1.21.1.
2. With the cursor inside the effective display area, push the left button, roll the
wheel to show “EBL OFFSET / EXIT” in the guidance box and then push the
left button.
3. Roll the trackball to place the offset EBL on a target appearing as threatening
(A in the illustrated example on the next page) and then push the left button
to anchor the EBL origin.
4. After waiting for a few minutes (at least 3 minutes), operate the EBL used in
step 1 until it bisects the target at the new position (A'). The EBL readout
shows the target ship's course, which may be true or relative depending on
the EBL bearing reference setting.
To return the EBL origin to the screen center, show “EBL OFFSET / EXIT” in the
guidance window and then push the left button.