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Old 24-01-2017, 03:15   #1
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AIS icon

When reading the request for inland ECDIS compatibility, I came across the requirement to have a different symbol for targets when there is no heading info available.
This seems to me a very good point.
Trying to have something for O as well I, my first test looks like this.
Please reply with comments.
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Old 24-01-2017, 11:00   #2
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Re: AIS icon

Dirk,

first: why do you think this is interesting beyond the restricted (in the sense of very limited space) Inland Waters? And there this is defined.

second: do you think we can test the correct implementation for InlandECDIS?
Some data stream or direct data at your location? Or shall we request test data to the corresponding body?
- this part is recommend for InlandECDIS in Information Mode, not mandatory. But we should handle it correctly anyhow.

Hubert
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Old 24-01-2017, 11:16   #3
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Re: AIS icon

Hubert,
I am not trying to make an inland ECDIS implemention, it was only the trigger that started me thinking .
To my opinion it is sometimes confusing to show an AIS target on a north course while there is no course info available. As the implementaition is now you have to check for the target prediction line to see if there is valid course info. (A target north course with prediction line is realy on a northerly course. when there is no prediction line the real heading could be anything.) And on a large scale there won't be a prediction line anyhow so you have to 'hoover over' to check the targets real heading.

But if I am the only one having this 'problem' we leave it as it is.

Dirk
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Old 24-01-2017, 11:27   #4
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Re: AIS icon

Dirk...

Nice work.
But I think it would be more intuitive if we stayed with the triangular shape, and adopted another color, or maybe a hash pattern color, for targets with no COG/SOG. Or maybe smaller triangles. I had to look at your image for some time before I got it. "Aha! Those little green squares are moored boats ...."

Keep thinking
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Old 24-01-2017, 12:19   #5
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Re: AIS icon

Dave,

that's my question: a moored boat has no COG but perhaps Heading (if the sensors are good). And a moving one has COG.

What are the situations to be resolved here?

(And perhaps I have not understood the complete InlandECDIS BlueFlag story yet)

Hubert
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Old 24-01-2017, 13:07   #6
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Re: AIS icon

Hubert,
A real life example. Happend to me the day before christmas.
Around 19:00 (dark) I come sailing with a WNW breeze. Intending to enter the port of Nes Ameland. (upper right).
On my screen I see a barge coming out of port, and then turning. At some moment (see screen shot) I have no idea what the barge is doing. Navigation lights not/hard visible in background lights from the port. But I do have its name from AIS and ask for his attention. Answer He will stay there to discharge a load of mud. So I inform him I will pass his stern.
????
No he was stemming the tide on an ESE course. So I was overtaking him and then cross its bow.
Do you see the confusing with a Nbound target icon with no valid heading?
(Sorry I had no VDR running so I had to make up the screen shot)
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Old 24-01-2017, 16:09   #7
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Re: AIS icon

Dirk...

Confused, but not argumentative.

Let us be sure we are super clear on the difference in the terms "heading" and COG.

Forget about barge's heading for a minute.

If the barge was underway ESE, with "some" SOG, then why was the icon rendered "north-up"? Maybe his SOG was too low? (see ais.cpp:around line 967.)

Or, if he was Class A (by the picture he is), then he "probably" has functional heading reported, so he was actually pointed north but making way ESE. Not surprising at low speed in a tidal stream discharging mud. Also explains why you could not read his lights.

So, how would your proposal change the presentation to make it more clear?

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Old 24-01-2017, 23:49   #8
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Re: AIS icon

Dave,
No the barge's SOG was 0. And therefore its COG anything.
For the inland AIS class A it is not compulsory to have a compass connected, and most of them don't have one. (See first screenshot. almost all 'squares' are class A. Only 1 with a heading alongside)
[offtopic] For autopilot they use a Rate Of Turn gyro. So the barge will keep its heading as long you don't touch the autopilot, or you can give a RoT order to sail a bent in a river. For barges this is far more convenient then compass steering [\offtopic]
If in my example the barge would have being plotted as 'no heading available', I wouldn't have thought it was on a Northerly heading, and in my radio conversation I would have said "I will pass south of you" instead of "I will pass your stern".
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Old 25-01-2017, 06:26   #9
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Re: AIS icon

Dirk...

OK, I'll condense. We are considering a unique symbolization when:

a) SOG is too low to give a meaningful COG

.and.

b) No HDG information is available, for whatever reason.

On our side of the pond, this will mostly be Class B targets while moored.

I still think we should use the triangle, in some undefined way/color pattern.

Ideas?

Thanks
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Old 25-01-2017, 07:07   #10
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Re: AIS icon

Dave,

why not following or imitating/adopting the InlandENC shapes and informations?

That's in the point 5.1 of the EU909/2013 (see the InlandECDIS thread, the link is wrong there pointing to 909/2014 instead of /2013)
EUR-Lex - 32013R0909 - EN - EUR-Lex

They distinguish four parameters
- heading information yes/no
- blue sign for passing not connected/not set/set
- blue cones for signaling dangerous cargo (outline of shape in red)
- displaying symbol (triangle) or rendered shape for vessel

The first one and the third we don't distinguish today, the second one as the blue half triangle - so not complete - and the last one yes, depending on scale.

I'm hesitating about the first parameter, as the ClassB targets don't have the heading and RoT information and drawing them all just as an octagon looks not very practical.

Hubert

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Old 25-01-2017, 08:27   #11
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Re: AIS icon

Should this be uploaded to OpenCPN Dokuwiki under MEDIA =opencpn:manual
as "ais_inland_ecidis_sym.png" ?

and inserted into the end of the AIS section with "Future Symbols" "Under development" ?

Later: Actually a separate page under AIS at the bottom under ATON

http://opencpn.org/wiki/dokuwiki/dok...ar_buttons:ais
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Old 25-01-2017, 08:45   #12
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Re: AIS icon

Rick,

this discussion still. Not implemented. So perhaps in stand-by.
The InlandECDIS EU directive is a "reference manual".

Hubert
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Old 25-01-2017, 10:08   #13
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Re: AIS icon

Dave,
a simple (red?) question mark on top?
Dirk
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Old 25-01-2017, 10:15   #14
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Re: AIS icon

Dirk,

another question: the "blue flag" and "blue cones" as InlandAIS signal are those mutual exclusive with the voyage status for ClassA (moored, not under command...)?

Hubert
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Old 25-01-2017, 10:52   #15
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Re: AIS icon

Quote:
Originally Posted by bcn View Post
Dirk,

another question: the "blue flag" and "blue cones" as InlandAIS signal are those mutual exclusive with the voyage status for ClassA (moored, not under command...)?

Hubert
Hubert,
A blue flag (now a days not a flag anymore) is used on rivers. when you go up river you would like in bents have the inside where there is less current. So if the river turns to the left you set a blue signal to indicate that you want the portside af the fairway and meet traffic starboard to starboard. So in practice you crossing the fairway very often.
If you are going down and see a upgoing vessel showing the blue vlag, you 'anwer' by setting also the blue flag, meaning you understood and will pass accordingly.

The blue cones is a total different story. The cones are telling that the vessel is transporting dangerous cargo. Where:
1 cone means flamable cargo
2 cones poison cargo
3 cones explosive cargo
Depending of the number of cones there are multiple safety rules as distance to stay free etc.

So the blue flag is changing a few times per hour depending of the curving river, and the cones are changing with the cargo/voyage
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