Why AIS makes sense

[Wanderlust]

Originally Posted by fgd3

If they want to do that all they need to do is code it as virtual, not real.

Fabbian

Not a good idea if there is actually a buoy floating there. If it's physically there I would expect the message to indicate that, regardless of whether it is transmitted from the buoy itself or elsewhere.

[fgd3]

Originally Posted by Wanderlust

Not a good idea if there is actually a buoy floating there. If it's physically there I would expect the message to indicate that, regardless of whether it is transmitted from the buoy itself or elsewhere.

Unless the AIS transmitter is actually on the buoy there's no guarantee that the buoy is actually where the AIS transmitter says it is. If a buoy drifts off station you want to know where it is, not where it is supposed to be.

Fabbian

[Jim Cate]

Originally Posted by fgd3

Unless the AIS transmitter is actually on the buoy there's no guarantee that the buoy is actually where the AIS transmitter says it is. If a buoy drifts off station you want to know where it is, not where it is supposed to be.

Fabbian

This depends upon whether you are trying to avoid hitting the buoy or hitting the obstruction that the buoy is supposed to mark!

In fact, both options are important!

Jim

[El Pinguino]

If a buoy drifts off station you are better off knowing where it is supposed to be than where it actually is....

If Captain Sillybugger has the 'AIS' fairway buoy on his ECDIS in the same location as the radar return from the buoy is he going to 'click' on the buoy and read the fine print or is he simply going to steer for it and end up on Dumbfugger Shoal? Especially if it is a long way offshore and there aren't a lot of other references to go by.... Beira and LM come to mind... not that many yachts go to either of them....

[fgd3]

Originally Posted by Jim Cate

This depends upon whether you are trying to avoid hitting the buoy or hitting the obstruction that the buoy is supposed to mark!

In fact, both options are important!

Jim

Your chart shows where the aid is supposed to be so you can avoid the obstruction it is supposed to mark.

An AIS transmission coded as real should be attached to the physical aid so you'll know if it is off station.

Fabbian

[El Pinguino]

Refer back to #11 ... if the AIS for the fairway buoy was generated elsewhere it would be synthetic .

A number of virtual AIS tx can be seen below.... including Astrolabe Reef which is 13 miles offshore from Tauranga... no physical marks as are half tide rocks and shoals.. I imagine the TX comes from Motiti Island.. close south.

A pity Astrolabe wasn't marked in 2011....

[fgd3]

Originally Posted by El Pinguino

Refer back to #11 ... if the AIS for the fairway buoy was generated elsewhere it would be synthetic .

And it wouldn't be coded as "Real", would it?

The point I was trying to make--and perhaps I failed to state it clearly--is that there is no reason for the authorities to falsely report the category of the target as suggested in #8. There are enough categories (Real, Synthetic, and Virtual) to describe properly the status of the target.

Especially with floating aids the advantage to having an AIS transmitter on the aid is that you can keep track of where it really is. Your chart shows where it is supposed to be. While you are proceeding towards the charted position in low visibility conditions it is helpful to see the actual position of the buoy so you can avoid hitting it. And if visibility is good enough that you can see the buoy the AIS message tells you if it is off position so you know not to rely on it but to use the charted position instead.

The disadvantage to Synthetic AIS messages is they cannot independently tell you the aid is off position. The buoy drifts off position but the AIS target doesn't follow it until someone notices the buoy has moved and changes the target data.

Virtual AtoNs never drift off station but they are invisible to those without AIS.

Fabbian

[barnakiel]

Yes. Atons are pretty common in Europe.

b.

[Ivanm]

I have a problem with ais , although it show the names of the vessels for some it only show a yellow ais icon with heading but no name. The ais unit that gives input to Open does show the name as well. Are there a setting that i mis someway

[bcn]

Ivan,

there is an issue with Static Voyage data for some vessels with a very recent version of AIS transponders and OCPN 4.4.0

Should be solved for 4.5 and the upcomming 4.6.0

[Dockhead]

Originally Posted by El Pinguino

Interesting.....

To the best of my knowledge AtoNs are 'synthetic' ... the buoy or whatever isn't doing the transmitting... that comes from a central TX in the Harbourmaster's office or wherever.

So that 'off position' buoy needed human intervention from ashore to adjust its position *after* it was observed and reported to be out of position. During the gale and when it was dragging it would have still shown as being at the start of the fairway.

They always used to teach us not to rely on buoys as they may be out of position........... nothing changes... this would be a case where - during the gale and before adjustment - I would rely on AIS rather than eyeball.....

Not on the UK. They have transponders. I don't know this for a fact, but I would guess that "synthetic" AIS positions would be forbidden by the protocol as potentially dangerously misleading EDIT: if the aid to navigation they are broadcasting physically exists.

Sent from my D6633 using Cruisers Sailing Forum mobile app

[bcn]

Dockhead...

look here:
https://www.nauticalcharts.noaa.gov/.../ais_aton.html

bcn

[Dockhead]

Originally Posted by bcn

Dockhead...

look here:
https://www.nauticalcharts.noaa.gov/.../ais_aton.html

bcn

I stand corrected -- thank you very much!

This has added to my knowledge

This:

http://www.eba.eu.com/site-documents...n-ais-aton.pdf

Seems to say that a "synthetic ATON" broadcasts from shore or another place, but reports real position and other data, received by other means from a real buoy.

It's a "virtual ATON" which does not report the real position of any navigational aid. These report reefs, wrecks, floating debris, etc., or buoys which do not exist physically.


I can't find any reference to the use of Virtual ATONs in cases where the buoy they are reporting, actually exists physically. I would think that this would be bad practice, but I would be interested to know more if someone has information.

[Ivanm]

Originally Posted by bcn

Ivan,

there is an issue with Static Voyage data for some vessels with a very recent version of AIS transponders and OCPN 4.4.0

Should be solved for 4.5 and the upcomming 4.6.0

Can be as it is new vessels that don't display data will test with 4.5

[Ivanm]

When I go to Menu, Ships, MMSI Properties, New what does the Persistent tick box do is it the same as always track?