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15. Navigation Sensors
2-19
2.14 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 in Figure (a). If the EBL passes through the
sweep origin (own ship) as illustrated in Figure (b), the target ship is on a collision course.
2.14.1 How to assess risk of collision by the offset EBL
From the control unit w/keyboard
1. Press the EBL ON key to display or activate an EBL (No. 1 or No. 2).
2. Put the cursor (+) on a target appearing as threatening (A in the figure below) by operating the trackball.
3. Push the EBL OFFSET key 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
below. If the EBL passes through the sweep origin (own ship) as illustrated in the right-hand figure below, the
target ship is on a collision course.
5. To return the EBL origin to the own ship's position, push the EBL OFFSET key.
By trackball
1. Display an EBL, following steps 1-3 in "By trackball" in section 2.12.1.
2. With the cursor inside the effective display area, spin the scrollwheel to show "Nav Marks" in the guidance area
then push the right button.
3. Use the trackball to place the offset EBL on a target appearing as threatening (A in the figure below), spin the
scrollwheel to show Offcenter REF pt then push the right button to anchor the EBL origin.
4. After waiting 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 deactivate the offset EBL and restore normal EBL operation, spin the scrollwheel to show the Nav Marks menu
and check "Centered REF Pt".
Collision assessment by offset EBL