19. Navigation Sensors
19-17
About alarm "2000 Filter: Pos unreliable"
If the filter is used with automatic route steering then, in case of alarm "2000 Filter: Pos unreliable", all position
sensors and the filter itself are switched OFF and the system continues with backup dead reckoning, based on
chosen speed/course sensors. In this case it is recommended that you leave automatic route steering and continue
using a more traditional steering mode until you find the reason why alarm 2000 was generated. If you don't leave
automatic route steering, the system will repeat alarm "2475 Route: Needs filter ON" every 15 seconds.
After the alarm 2000 is generated, the operator should leave automatic route steering and evaluate which sensor
caused the problem. If the ship position from a position sensor is acceptable, switch it on. Don't choose any sensor
which causes jumping. Then, you can turn the filter ON again and continue automatic route steering.
19.8 Position Alignment
The position alignment feature functions to fine-tune ship’s position by using radar overlay, radar echo target and
ECDIS chart material.
If position alignment is in use, the ECDIS will generate the following alarm every 30 minutes to remind the operator
to align position: "2352 ChartAlign: over 30 min".
19.8.1 Position alignment by means of the ECDIS
If the radar echo targets' symbols are not positioned correctly, there is either position error or gyro error or some
combination of these errors.
Position may be aligned on the ECDIS display by moving your ship's position or by moving ARPA radar target
position. Moving is done by dragging and dropping your ship symbol or ARPA radar target to desired location. Drag
and drop means that you place the object on desired location by rolling the trackball while pressing and holding
down the left mouse button then "anchoring" the object by releasing the left mouse button.
Note: If the radar overlay is on the ECDIS display when position alignment is done, then
• Mode of radar overlay is temporarily changed to "Radar over Chart".
• ECDIS temporarily uses radar overlay color also for your ship and ARPA targets symbols.
To align position, do the following:
1. Choose desired chart material (ARCS or S57).
2. Choose suitable radar target manually for tracking.
3. Place the cursor on the position indication in the information area then push the right mouse button to display
the Sensors dialog box. Open the Position page, then check Enable chart align.
Spd/Cse Posn
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