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Position alignment by means of the ARPA radar
User chart, showing coast line, buoys, etc., can be used as a position reference once the ARPA radar is able to see
these objects. If the ARPA radar targets and the User Chart are not exactly overlapping there is either position error
or gyro error or some combination of these errors. Some selected ARPA radar modes which can display User Charts
can perform position alignment.
ARPA Radar with CHART ALIGN push-button
1. User chart must be available on the radar.
2. Press CHART ALIGN push-button on the ARPA radar display once. Then use ARPA radar
display track ball and move the User Chart so that it overlaps correct radar echoes. Press
CHART ALIGN push button again once. Then the amount of alignment is transferred to the
ECDIS.
3. If the position source is Dead Reckoning, then CHART ALIGN set a new start position to the
Dead Reckoning. In this case there is no offset and no indication text OFFSET. If the
position source is something else than Dead Reckoning, then the indication of OFFSET is
displayed on Upper information area. See Figure below.
Upper information area on ECDIS screen.
ARPA radar without CHART ALIGN push-button
1. User chart must be available on the ARPA radar. (ARPA radar must be connected to the
ECDIS and STORED VIDEO MAP pushbutton of the ARPA radar must be pressed). Press
Sensors button and select Position sheet open.
Press Start button to
alignment with radar.
2. On the ARPA radar screen, locate a clear reference radar echoes and suitable User Chart lines
or symbols.
3. Press Start button in Position sheet. If there was no User Chart lines on the ARPA radar
display, then system is unable to continue and generate alarm "2072 ChartAlign: No line
avail". If there was User Chart lines on the ARPA radar the system can continue and as a
reminder of the ongoing process it generate and maintain alarm "2061 Chart Align:
Executing" during the whole process.
4. Use the track ball of the ARPA radar and move the User Chart so that it overlaps radar echoes.
310 • • • • Navigation Sensors
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