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3. ARP OPERATION
3-3
3.3 Activating, Deactivating ARP
To activate or deactivate the ARP:
1. Roll the trackball to place the arrow in the ARP ACQ MODE box at the right
side of the display. (Note that “ATA” replaces “ARPA” when the ATA feature is
used.)
ARPA
AUTO
MAN
ARPA ACQ MODE box
2. Push the left button to show OFF, MAN or AUTO MAN as appropriate.
3.4 Entering Own Ship's Speed
The ARP requires own ship's speed and heading data. The speed can be STW,
BT, SOG or echo-referenced speed (based on 3 max. stationary objects).
Manual input is also possible.
For automatic or manual input, see paragraph 1.13. For echo-referenced speed
input follow the procedure below.
3.4.1 Echo-referenced speed input
The use of echo-referenced speed is recommended when:
• The speed log is not operating properly or not connected to the radar.
• The vessel has no device which can measure ship's leeward movement
(Doppler sonar, speed log, etc.) when leeward movement can not be
disregarded.
If you select echo-referenced speed, the ARP calculates own ship's speed
relative to a fixed reference target. The number of targets may be 1, 2 or 3. They
appear as tracked targets, each shown in a small circle. When a plural of objects
are selected, the mean value is used for stabilization and speed.
1. With the cursor inside the effective display area, roll the wheel to display
“REF MARK / EXIT” in the guidance box.
2. Select a small fixed island or any radar prominent point located at 0.2 to 24
nm from own ship.
3. Roll the trackball to place the cursor (+) on the target selected at step 2.