a question for the AIS experts...

[winsbury]

Are the new uses for AIS - specifically AIS-SART and Buoy transmissions compatible with early AIS receivers which were intended only for class A and B reception or does older AIS reception equipment need to be swapped out now ?

 

[prv]

AIS SARTs send two message types. Can't remember the numbers off-hand, but one is the same as the dynamic data from a ship. The other is more unusual (though I don't think it's exclusively for SARTs) and probably not supported by older kit.

So in practice, nearly all old displays will show a SART or MOB device, but it will look like an ordinary ship. You can tell it's a SART because the MMSI starts with a particular set of digits, but the display won't set off any alarms or do anything special with it.

It's unlikely but possible that the second message type will confuse a poorly-implemented and poorly-tested device - some Garmin plotters would actually crash if an AIS MOB was set off within range! Garmin did fix that one within a couple of days when it was discovered.

A modern device will display an AIS SART or MOB as a red cross in a circle and presumably set off some kind of alarm - I know mine does.

The purpose of these beacons is to allow a crewed boat to return to its own casualty. So assuming you noticed that your crewmate fell off, even with an old plotter it should be obvious what's going on when the "ship" suddenly appears almost on top of you. So although if you buy a beacon then a new display (or firmware update) would make things clearer, I wouldn't say it's essential. And I certainly wouldn't be looking to re-equip in order to pick up beacons that other people might have - while other vessels noticing the alert is a bonus, it's not really what the system is about.

Pete

 

[knuterikt]

Are the new uses for AIS - specifically AIS-SART and Buoy transmissions compatible with early AIS receivers which were intended only for class A and B reception or does older AIS reception equipment need to be swapped out now ?

The problem is not with the receivers, they will receive and and send all AIS data out on the NMEA (0183 or 2000) port.
The problem is with the display units that is filtering out (and not showing at all) or that the display show the target as a normal AIS target - in both cases no alarm.

I have an Em-trak B100 that is connected to
-Furuno NN3D via NMEA 0183 (only support for AIS data on 0183 even if it has got N2K support)
-Raymarine i70 via NMEA 2000 (SeatalkNG)

We tested this setup with a AIS-SART (it's not illegal to set of an AIS-Sart yet...) using a McMurdo smartfind S10
The i70 raised an alarm while the NN3D ignored the target (and no alarm)

Furuno didn't believe us so we had to prove it before the would accept it as a bug - but still 18 months later no new SW..

If you are planning on buying AIS-SART you should verify that it's working with your equipment.

 

[prv]

The problem is not with the receivers, they will receive and and send all AIS data out on the NMEA (0183 or 2000) port.
The problem is with the display units

True - my reply implied this, talking about displays and plotters rather than receivers, but perhaps I should have stated it specifically.

We tested this setup with a AIS-SART (it's not illegal to set of an AIS-Sart yet...)

Indeed, although the instructions do recommend refraining from testing it in a busy area . The range is only a couple of miles on the typical MOB unit, as they were invented to help racing boats recover their own MOBs in the Southern Ocean, not to transmit a distress call to a third party. So it's not like setting off a PLB or a VHF DSC. The Kannad and McMurdo one can do a test transmission - a compatible display will show "MOB TEST", but again who knows what an older one will do.

the NN3D ignored the target (and no alarm)

That's interesting - when you say "ignored", do you mean it didn't display it at all? That's concerning, I had thought that all devices would at least display the basic position message even if they rendered it as a ship.

If you are planning on buying AIS-SART you should verify that it's working with your equipment.

Exactly.

To reiterate, AIS MOB units are a more modern replacement for the round-the-neck analogue beacons where you also had to carry a dedicated receiver. The clever part is that now you get to re-use equipment you already have as the receive side of the system. But it is still a system, the beacon isn't a standalone device, and you need to check that the system as a whole works on your boat.

Pete

 

[laika]

I noticed that virtual aids to navigation (specifically the buoys I'd had to put "AIS" in magenta next to when updating charts) weren't showing up on my C90W (which has the "latest" (2012) firmware). I contacted Raymarine who told me that it doesn't and never will display AtoN stations as the C90W was retired "many years ago". Which is odd as they were still selling it besides their newer plotters until about a year ago.

 

[winsbury]

Interesting, lots more devil in the detail.

In my particular case I have an original EasyAIS Mk1 receiver hooked up to a modern Lowrance HDSgen2 plotter via an Actsense ais 0183 to n2k converter. There were some initial problems with the plotter not displaying ship names etc although positional data was displayed correctly. After much head scratching it turned out to be a bug in the converter which Actisense has now patched and was very helpful throughout.

I'm hoping that if a SART is set off or a beacon buoy is within range that the data will get through to the plotter and the plotter, being modern, should interpret it correctly but this clearly depends on if there are any more fundamental mismatches lurking.

Having no way to test the system integration except in earnest feels a bit like navigating in fog. Its crazy there isnt a central testing body that certifies compliance for such essential equipment.

 

[prv]

Something else worth pointing out in relation to older plotters.

There is at least one device out there which you can wire into your AIS feed in parallel with a display, and it will quietly watch for MOB and SART messages going past. If it sees one, it sounds an alarm and closes a relay that can be used to activate other things. If you have a plotter which does the display-as-ship thing, this might fill the gap, particularly if you sail two-up and think the MOB might not be immediately noticed. The extra box will sound the alarm, then the remaining crew can use the "ship" on the plotter to get back to their partner.

Pete

 

[knuterikt]

Indeed, although the instructions do recommend refraining from testing it in a busy area . The range is only a couple of miles on the typical MOB unit, as they were invented to help racing boats recover their own MOBs in the Southern Ocean, not to transmit a distress call to a third party. So it's not like setting off a PLB or a VHF DSC. The Kannad and McMurdo one can do a test transmission - a compatible display will show "MOB TEST", but again who knows what an older one will do.

We did this with the boat in harbor and the AIS-Sart ashore during winter.

That's interesting - when you say "ignored", do you mean it didn't display it at all? That's concerning, I had thought that all devices would at least display the basic position message even if they rendered it as a ship.

Yes, nothing at all...
After we documented that the Furuno indeed got the correct data from the AIS receiver the replay was that it was filtered because "Some AIS SART report L/L COG or HDG feltet = empty field, and get filtered out by the NN3D"

 

[winsbury]

Yes, nothing at all...
After we documented that the Furuno indeed got the correct data from the AIS receiver the replay was that it was filtered because "Some AIS SART report L/L COG or HDG feltet = empty field, and get filtered out by the NN3D"

Errors can happen both ends - either the message is malformed by the transmitter or the display is misinterprets a properly formed sentence but common sense would dictate that in either case it should display 'something' possibly with an unreliable data warning rather than filter out a help message entirely.

 

[prv]

Errors can happen both ends - either the message is malformed by the transmitter or the display is misinterprets a properly formed sentence

Yes, but Knuterikt says they had valid data coming out of the AIS receiver - it's easy enough to check with the right hardware. So the problem was definitely in the Furuno plotter.

Pete

 

[knuterikt]

Errors can happen both ends - either the message is malformed by the transmitter or the display is misinterprets a properly formed sentence but common sense would dictate that in either case it should display 'something' possibly with an unreliable data warning rather than filter out a help message entirely.

As I wrote Furuno finally did accept is as a bug - but have not done anything to fix it.

In reality we did two tests
First we only set of the AIS-SART and found that it did show up on the Raymarine i70 but not on the Furuno NN3D.
Furuno said it was not there fault and asked us to use the port monitor on the Furuno to verify data from the AIS, this proved useless as the speed of data coming in made it impossible to read anything (and there is no logging functionality).

The Furuno NN3D use Ethernet to communicate with other NN3D dislplay and uses UDP to broadcast NMEA data to other devices.
My brother found a way to capture these UDP packets and strip the UDP envelopes of the messages and send to Open CPN, this way we could tap the data that the NN3D received.

So with this setup we did test no two.

This is the alarm on the i70 just after the AIS-SART was set of - before the AIS-SART got GPS fix.

This is the Open CPN screen at this point in time we got position also, note the missing speed & heading.

Nothing showing on the NN3D

After presenting this evidence I was hoping that Furuno would do something, but almost a year later no update.
I doubt Furuno will get on my short list the next time.

 

[prv]

After presenting this evidence I was hoping that Furuno would do something, but almost a year later no update.
I doubt Furuno will get on my short list the next time.

Unfortunately, plotter makers often don't seem to consider AIS a priority. They implement enough to tick the box but little more.

When fitting out Ariam, having been disappointed with AIS on the previous boat's Standard Horizon plotter, I opted for a dedicated display from Vesper. This company does nothing but AIS, so they're always at the forefront of what's going on and they implement all the features properly. They're also quite responsive to customer feedback and have accepted a couple of my suggestions for inclusion in future versions. The Vesper Watchmate is vastly more useable than the plotters I've used (admittedly I haven't used anything really cutting-edge).

Pete

 

[srm]

Plotter and AIS do not always work together with ships even.
Last year fitted a new ICOM AIS TX/RX, the one with its own display as I prefer that my toys can stand alone when one goes down. Connected NMEA to Standard Horizon plotter. All worked well for a couple of weeks with targets showing along with data on the plotter and AIS screens. Then had an alarm on the AIS with message saying no TX power. Shutting down and restarting cleared the problem. After the second occurence contacted ICOM who's technician was puzzled but kindly exchanged the set.
Once new set was working discovered that interogating one target in the harbour caused plotter to shut down and restart. Other targets were displaying correctly. One day into our passage to the Azores we had another target shut the plotter down. The following day an AIS alarm display showed no TX power.
A pair of sidecutters disconected the carefully soldered NMEA wires and no further problems have occured. My 'stand alone' policy paid off.