Mark-1
Well-Known Member
Are you sure? I can't see anything in ITU‑R M.1371 and I can't see how that would work on a gazzilion ton ship. (Happy to be corrected.)
AIS permanently on, do you?
- Thread starter GEM43
- Start date
Are you sure? I can't see anything in ITU‑R M.1371 and I can't see how that would work on a gazzilion ton ship. (Happy to be corrected.)
lustyd
Well-Known Member
I’d agree when we’re at sea crossing a TSS, we rely on AIS a lot.
In harbour is entirely different, that’s pilotage.
In fog RADAR is far more important, I certainly wouldn’t rely on AIS anywhere in fog.
lustyd
Well-Known Member
If alarms are a problem in port, the alarms should be turned off. It’s not hard to do and the alarms add nothing to safety during pilotage (neither does AIS, really).
Boats are in and around ports more than at sea so alarms should usually be off and turned on when leaving for a passage. Same for RADAR guard zones etc.
Sjp1960
New Member
My Garmin has a limit of 100 AIS targets ( ie it shows the closest 100). The AIS receiver can handle far more than this. In the Solent this means that the effective AIS range can be limited near marinas. I would prefer ( for the Solent at weekends) that the chart plotter had an option to filter out class B targets and so just show big ship movements.
laika
Well-Known Member
Also happy to be corrected because it’s a few of years since I researched this but I believe the requirement is “dedicated” gps rather than “in-built”. I’m guessing this is because a ship may have multiple sources of gps data and the data on receiver position should be correct as on a large vessel if the wrong gps were used that could alter the vessel’s position by a non trivial amount.
On a small yacht no-one cares, although my raymarine AIS at least does have its own gps
Baggywrinkle
Well-Known Member
There are shipping lanes on the approach to Rijeka in Croatia which I regularly end up in, and numerous extremely fast ferries which can appear from nowhere as they dash between the islands. AIS is a great tool as it gives me CPA info (time and distance) for my current course, which I can then adjust by slowing down, or turning slightly to increase the CPA distance. It can also tell me if a fast ferry (travelling at around 40 knots) is about to round a headland and come barelling towards me, or if the ferries that criss-cross back and forth to the islands have cast off and are about to appear from behind a headland. None of them give any quarter even if sailing, so it helps enormously. Using the AIS bearing to the target also enables me to pick out problem targets from the plethora of other boats out and about - so IMO it is a very useful addition to enhance keeping a lookout with some tangible data.
As for "Is it on all the time?" ... my transponder only comes on with the main instruments (Plotters, radar, autopilot, VHF etc.) ... the other instruments are on all the time that the battery master switch is on so I can watch wind speed and direction, as well as depth and position when at anchor.
lustyd
Well-Known Member
Yes it can be useful, for those who know how to use it. You don’t seem to be having issues with overcrowding and alarms so my comment wasn’t aimed at you
wonkywinch
Well-Known Member
I think it's more to do with the quality of data rather than raw position. Even on a bog standard Raymarine/B&G leisure AIS transceiver, you can offset the position in the settings putting yourself 100m ahead/behind your actual position.
The commonly used B&G NAIS500 uses an external aerial.
ylop
Well-Known Member
Could be different for class B? I remember reading something about it on Digital Yacht website which said they couldn’t have an NMEA input for the GPS.
Harbours come in all sorts of shapes and sizes, but even in marinas or small harbours (like Tayvallich) it’s not a bad thing to be able to see at a glance if a boat is motoring out or just swinging around. The limiting factor there is not all vessel (including mine) transmit AIS. Of course my idea of busy (Oban bay) and a typical Solent Sailor’s are different.
I thought AIS did prioritise class A targets in busy areas? Perhaps that is only for transmission not display.
Most of the issues here are actually user interface issues with plotters rather than a flaw of the AIS system in general. The ability to change “mode” seems useful but if it requires reading the manual it’s pointless! The ability to mute alarms seems good but if it is three menus deep and risks you forgetting to turn it back on then it’s not good. Filtering closest vessels is logical but actually you want those with the nearest CPA - the guy who has just passed you and is motoring away from you is less relevant than the two miles away heading straight for you at 20 knots.
lustyd
Well-Known Member
I agree we did use it in Oban to see when the CalMac was coming, but then I’m not concerned by the alarms or overcrowding. We also used it in the Solent to see the various ferries and ships, again with no issues at all.
We didn’t need it, it was pilotage and we’d have been fine without but it is nice to see and we have our alarms off in and near harbours.
Contrast that with Arklow to Newlyn where we were between three TSS for 24 hours and AIS was essential along with alarms and sometimes radar to spot fishing vessels. We probably still had 30+ targets most of the night and were glad to see them! Even then the alarms are set to 0.2NM CPA.
ylop
Well-Known Member
It’s never essential! We sometimes forget that some of the old gits on here managed just fine without a chartplotter never mind having the moving targets drawn on the chart!
lustyd
Well-Known Member
I could manage without a plotter but my sailing would be very different! I think we’ve all become more adventurous as technology has improved. The confidence of having plotter, radar and AIS available is enormous.
AndyDavies
Active Member
One problem is it triggers constant and unnecessary proximity alarms for others sailing near the marina.
lustyd
Well-Known Member
Only if they have alarms set while sailing next to a marina. The question is why do they?
Momac
Well-Known Member
Not really a problem .
The audible alarm can be switched off. The targets flash when on a collision course but that's really not an issue .
Anyhow get used to it as no law/regulation is being broken and there is no change likely.
Porthandbuoy
Well-Known Member
My AIS is on the same circuit breaker as the VHF. If there's power to the radio then the AIS is on, even when the radio itself is turned off.
Using OpenCPN on my Android tablet I tick 'suppress anchored/moored targets' set at 0.5 kts. I can still see them, but OpenCPN doesn't raise any CPA or TCPA alarms.
Using OpenCPN on my Android tablet I tick 'suppress anchored/moored targets' set at 0.5 kts. I can still see them, but OpenCPN doesn't raise any CPA or TCPA alarms.
st599
Well-Known Member
My mistake, the ITU spec has the data format, there's an IEC spec for class B (62287-1).
https://www.navcen.uscg.gov/sites/default/files/pdf/AIS_Comparison_By_Class.pdf
MikeBz
Well-Known Member
For Class B that says "Internal GNSS only, interface to an external GNSS is optional". From that I conclude that everything which has been written in this thread about it being against regs for the AIS receiver's GPS source to be from a separate source which can be switched off (e.g. plotter) is wrong with regards to class B.
wonkywinch
Well-Known Member
I wouldn't trust that document. Firstly it relates to USCG regs, secondly it's been produced by a third party, possibly at USCG who used Microsoft Word and then generated a pdf and didn't bother to title it correctly.
Any official sources?
Sjp1960
New Member
That’s correct AIS class A transmissions are prioritised over class B. I believe that Class B+ actually has the same tx priority as class A.
The Garmin simply displays the closest 100 targets and so a big ship in the Nab channel received by the AIS receiver and broadcast over N2K may not be shown because of stationary boats in the Portsmouth marinas! I can connect a terminal directly to my AIS receiver and see a list of all > 100 targets that it can see.
It’s a very minor thing and only applies in busy areas, but I would welcome an option that filtered out class B clutter and so let me just keep an eye on big ship movements in the Eastern Solent like it used to be when I first got an AIS 16/17?? years ago.