OpenCPN not reporting a special NMEA 2000 AIS target

[SoggyPaws]

Reported on the OpenCPN Users FB Group, thought I'd pass it on to the developers:

Person has a Raymarine Axiom Chart Plotter and OpenCPN (version and flavor unknown atm, but has been asked). The targets show up on their chart plotter, but not on OpenCPN. When queried:

- The targets are actually (visually) fishing net markers in the Indian Ocean
- Data coming in to OpenCPN via Wifi from Axiom connection as NMEA 2000
(I don't know the details of this).
- Target MMSI's that don't show up in OpenCPN are (for example)
005030101, and 005030105 See attached shot from Axiom display
These 2 MMSI's show in Marine Traffic as SAR Airplanes registered in Australia, last seen in January in PNG.
- Other more normal targets are displaying normally in OpenCPN
- Person seems familiar with OpenCPN and competent with his system.

See attached graphic--list of MMSI's from the Axiom. If I get OpenCPN version details, I'll come back and report. Just thought you ought to know. Maybe this is a feature and not a bug!

[SoggyPaws]

We have a lot of fishing boats with sketchy AIS signals here in the Straits of Malacca. I found one currently on my target list with a similar MMSI pattern and Class=Base Station near me, and OpenCPN is showing it. Vesper 850 connected via NMEA 0183. OpenCPN 5.8.2 on Windows 11.

[Hakan]

The mentioned MMSI (005030101, and 005030105) are not according to standard. Starting with "00" is a coast/base station.

From ITU-R M.585-8: (MID= country code)
a) 00MID1XXX Coast radio stations
b) 00MID2XXX Harbour radio stations
c) 00MID3XXX Pilot stations, etc.
d) 00MID4XXX AIS repeater stations

A fishing net buoy is not yet covered by any standard. There is no recommendation to local authorities how to handle such a transponder. If anyone use such a buoy they often try to invent an "own" MMSI-number but without a valid registration.

Local authorities would be able to give a permission but as an AtoN with a MMSI like 99MID1XXX, i.e. physical AtoN.

I know some has used "941MIDXXX" but it's not validated. (Will show up as a class B ship since message 18 will be used mostly)

With no local authorization the fishing net AIS transponder is not legal to use inside any territorial borders.

And if the MMSI number is not according to any known standard OCPN may omit to use it.

[s/v Jedi]

Originally Posted by Hakan

And if the MMSI number is not according to any known standard OCPN may omit to use it.

That would be very bad for the user and, if true, needs to be fixed asap. It is not for OCPN to decide who to display and who not; all received targets must be displayed.

[Hakan]

Jedi..
I may have used a misleading word, sorry.
As long the mmsi part of the VDM, or other AIS messages, is not empty OCPN will try to use it.
The target Type for a unknown structure of the mmsi will be "undefined" but still listed.
Based on the VDM message number it may also get a Class, like A, B, Base....

[s/v Jedi]

Originally Posted by Hakan

Jedi..
I may have used a misleading word, sorry.
As long the mmsi part of the VDM, or other AIS messages, is not empty OCPN will try to use it.
The target Type for a unknown structure of the mmsi will be "undefined" but still listed.
Based on the VDM message number it may also get a Class, like A, B, Base....

Oh that’s great news! Phew

[wholybee]

I wonder if the Axiom is filtering AIS targets?
I have seem Opencpn display all sorts of malformed/invalid mmsi numbers.
All zeros, all nines, 1234567890 etc. Usually fishing nets. I've also seen vessel names as "11.4V2.1A" on what appeared to be some sort of drone. Apparently a way to monitor battery status.
Anyway, i think a recording of the nmea2000 data would be helpful.

[LeaseOnLife]

I have a sneaking suspicion that the AIS sends N2K PGN 129040 for these targets. which O does not support despite my report on 11/2022 of this problem during the last beta phase:

Originally Posted by LeaseOnLife

please don't forget PGN 129040: I got that from my N2K AIS when encountering Chinese fishing vessels, they marked their net with AIS buoys.

N2k=>signalk=>N183=>OpenCPNn did not display those ais targets
N2k=>iKommunicate=>N183=>OpenCPN did display them
N2k=>B&G Zeus did display them


for more explanation:
https://github.com/sbender9/signalk-...a0183/issues/8


I don't have a N2K dump with 129040 though..

https://www.cruisersforum.com/forums...ml#post3678353


In April 2023 I did send DaveR a candump that contained PGN129040.



Nothing heard since then!

[SoggyPaws]

Originally Posted by LeaseOnLife

I have a sneaking suspicion that the AIS sends N2K PGN 129040 for these targets. which O does not support despite my report on 11/2022 of this problem during the last beta phase

That's what I'm thinking. The code processing 0183 AIS is completely different than the code processing the NMEA 2000 AIS signals. (I looked through it trying to see why it was getting filtered, but got "boggled".)

I think this is a bug that ought to be looked into. I can definitely see the 0183 AIS signals from targets with (I think) identical characteristics (A Base Station and a similar number pattern). The Chinese fishing boats with many longlines are using them all over Asia.

While on the subject, it sure would be nice to flag a "SART" signal (by individual MMSI) that is not really a SART but a $%#@! fisherman using a SART as a net buoy. They are all over in the Malacca Strait and it's really annoying. This should take a little effort (at least an "are you sure?".

[LeaseOnLife]

It is not just the Chinese longliners, but here in French Polynesia the local fishing boats use them too. Here is one close enough to a marinetraffic shore station to actually be shown as a fishing buoy. The second pic is a bit zoomed out, showing orange/brown fishing ships, each surrounded with these grey AIS targets. That could well be the AIS fishing net / longline markers.
when my AIS receives a signal from these type markers, it issues a PGN 129040 for that target.

[Hakan]

What the world would need is a recommendation from ITU how to handle fishing net buoys. Who can convince them to act?
Now it's the laws of the jungle leading to all kinds of private inventions.
That's not easy for OCPN to cope with.

[Hakan]

To add PGN 129040 would be possible I suppose. Everything is possible if time and energy is there. Anyone can make a request to add code.

[LeaseOnLife]

Originally Posted by Hakan

What the world would need is a recommendation from ITU how to handle fishing net buoys. Who can convince them to act?
Now it's the laws of the jungle leading to all kinds of private inventions.
That's not easy for OCPN to cope with.

My old, 1st generation, ZEUS8 displays this N2K PGN 129040. I am happy these fishermen use 'something' to mark their miles-long long lines, or nets.

My take: Anything that can be at least decoded to a lat/lon should be displayed. If there is more info (COG/SOG), even better.

[s/v Jedi]

Originally Posted by LeaseOnLife

My old, 1st generation, ZEUS8 displays this N2K PGN 129040. I am happy these fishermen use 'something' to mark their miles-long long lines, or nets.

My take: Anything that can be at least decoded to a lat/lon should be displayed. If there is more info (COG/SOG), even better.

Completely agree; even when it’s the ghost from the Flying Dutchman, plot it

[Hakan]

Now the Dutchman's didn't make a mmsi-number rule for that. Only a "diver's radio" See here