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Old 03-05-2014, 15:10   #1
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CPA Warning Vector Missing

I was returning to port today with two instances of OpenCPN 3.3.1606 running side-by-side. Another vessel came up across the river on my starboard side, causing a red-yellow CPA vector to appear (see right pane on screen shot). This warning vector stayed up on the display for several minutes. The instance of OpenCPN on the left had the exact same AIS settings, and received the exact same data, but did not display the TCPA vector. Any idea why the left pane did not show the vector?

There was no safety issue involved here, but I am concerned about the lack of a vector in the left instance. I consider that vector very informative and would want it to show up at both zoom levels, especially in a safety-critical situation.



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Old 03-05-2014, 18:21   #2
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Re: CPA Warning Vector Missing

RhythmDoctor...

The left screen has "Suppress Alerts for Anchored/mooored targets" checked. The target of interest is reporting "Moored" (note black "anchor ball" symbol). So, the CPA alert is suppressed.

Sharp readers will note that the target in the main channel is actually moving. He is not likely to be dragging at several knots directly upstream. The ship's Master or Pilot often fails to reconfigure the AIS transponder on weighing anchor. We see this often....

We choose to honor the target anchored/moored status bit, even though it is patently incorrect. It is thought to be best practice to simply report AIS status without creative editing.

Dave
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Old 03-05-2014, 20:17   #3
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Re: CPA Warning Vector Missing

Dave,

Well that makes sense! Thanks, I didn't notice that.

I unchecked all the CPA/TCPA boxes on the right side because I don't need duplicate AIS alarms, but I didn't realize the "suppress" box would continue to have relevance. I guess I should have realized, since it wasn't greyed out.

I, too, have learned to totally ignore any of the manually entered status and destination information because of its inaccuracy. I've seen a lot of ships who reported their destination as "Philadelphia" who were headed the wrong direction. Their GPS SOG and COG data do not lie, so I pay attention to that instead.

In the screenshot, I hadn't noticed the black dot on the icon indicating that it was supposedly moored. I totally noticed the 1 nm long 5 minute predictor vector, indicating a speed of about 12 kts. That's much more important (and accurate) in most cases.

I'll change uncheck the "suppress" box on the left side.
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Old 04-05-2014, 02:17   #4
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Re: CPA Warning Vector Missing

Quote:
Originally Posted by bdbcat View Post
RhythmDoctor...

The left screen has "Suppress Alerts for Anchored/mooored targets" checked. The target of interest is reporting "Moored" (note black "anchor ball" symbol). So, the CPA alert is suppressed.

Sharp readers will note that the target in the main channel is actually moving. He is not likely to be dragging at several knots directly upstream. The ship's Master or Pilot often fails to reconfigure the AIS transponder on weighing anchor. We see this often....

We choose to honor the target anchored/moored status bit, even though it is patently incorrect. It is thought to be best practice to simply report AIS status without creative editing.

Dave
I wonder if there is something what we are missing (despite of the obvious operator errors in the static AIS data).

If you look into the timing information for AIS messages you will find entries like:

Quote:
Class A
- At anchor or moored and moving less than 3 knots: 3min
- At anchor or moored and moving faster than 3 knots (!!) 10s
- 0 to 14 knots 10s
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