AIS

[Lucky Duck]

This is just another example of why decent filtering is important. Dare I say Watchmate again? They can ignore targets that are not moving.

No, I'm not on commission, but it's this kind of issue due to lack of thought and experience on the part of the designer that drove my research to find a solution other than a plotter with AIS tacked on as an afterthought.

Pete

From my persepctive, a filter for class B units would be sufficient as I am more relaxed about being 'alarmed' by the big stuff.

Unfortunately there is nowhere immediately obvious to install a seperate AIS display - such as the Watchmate - on board.

 

[prv]

I am a little surprised that it is possible to disable the reception of Class B versus Class A, since my understanding is that they broadcast on the same frequencies but with Class B at a lower priority and power.

Well, strictly speaking it doesn't disable reception, it disables display. That's a trivial change to the software.

Certainly it would be easy to disable display of Class B, but there seems to be some doubt over whether the facility actually is provided.

Pete

 

[boatmike]

This thread has followed a sadly predictable direction into technical detail. It has also illustrated a problem I have been bleating on about for over 4 years on here which is that the proliferation of class b transmissions by small craft has reduced the usefulness of AIS for everyone in crowded waters.

Your question seems to imply that you don't currently have a chartplotter for "normal" navigation. If I have got that right this should be your priority and there are many on the market like the Standard Horizon at reasonable cost. Most are now AIS ready and you can buy a reciever only to integrate with it for small bucks. If you fit one you will, like most of us get an overwhelming number of alarms and eventually, like most of us, switch the damn thing off in crowded waters where Mk 1 eyeball and or RADAR if you have it does a better job anyway. When away from crowded waters we normally switch on because it is useful when say crossing traffic lanes to know the course and speed and name of other vessels. If nothing else it is an AID to judgement and gives you better info with it than without it.

Here is the danger though. If you can't be sure if the other vessel is either switched on (or watching) ALL of the time then a transponder won't ensure you have been seen or not. A SeeMe or similar has a better chance of ensuring that you are seen by bigger vessels than AIS does without doubt, but even than it it prudent to assume a paranoid state and assume the other guy is out to get you. There are old sailors and bold sailors but few old bold sailors.....

 

[Rivers & creeks]

Your AIS transponder will almost certainly not be seen by a ship, your SeeMe will almost certainly be seen.

 

[prv]

Your AIS transponder will almost certainly not be seen by a ship

I think that's taking things a bit far. I read the MAIB report mentioned in YM this month about a radar-assisted collision between a yacht and a gas tanker on the east coast. It said that the gas tanker had AIS targets displayed on its radar screen, and the yacht would have showed up if she had had AIS transmit (which she did not). The tanker was built in 1997 so not brand new.

Many ships do display AIS on their radar or another primary graphical screen. The problem is that not all do.

Pete

 

[BrianH]

Many ships do display AIS on their bridge. The problem is that not all do.

If, by "ships" we are referring to commercial vessels over 300 tons or others with 12 or more passengers, with exeptions such as fishing or warships, then legally, according to the IMO recommendations and rules, they are obliged to have AIS transmit and recieve units. For receiver display the AIS system should have as a minimum a control panel in the form of a MKD (Minimum Keyboard Display). Alternatively and preferably, the AIS can be connected to the external navigational system (e.g., ECDIS) without a MKD, if the latter itself provides the MKD functionality.

Four types of AIS display can be identified:
- an alphanumerical MKD display
- a graphical MKD display
- ECDIS/ECS
- ARPA - Radar

Therefore, a basic alphanumerical MKD display is only going to add your ship's report to a monochrome display that may be limited to only a three-report display far from the radar screen and never consulted. Additionally, there may be no CPA alarm activated. The true benefits of AIS cannot be realized unless it is integrated with a vessel's bridge navigation systems, such as electronic chart display and information systems (ECDIS) and automatic radar plotting aids (ARPA).

A few years ago, and so hopefully no longer up-to-date but should still be borne in mind as pertinent to many ships, 'The Pilot', the magazine of the United Kingdom Maritime Pilots' Association, published a report from one of its members as follows:

"With respect to the type of equipment installed, the overwhelming majority of vessels are fitted with the minimum required to comply with carriage regulations! These are small alpha numeric displays which at the absolute basic level have to display at least three targets. I have seen such minimal three line units on ships and for all practical purposes they are totally useless. Other systems cram a list of many targets into the small display (typically 9cm x 12cm) which renders them illegible and again these are totally useless.

It is of extreme importance to the Class B user to be aware that there is no statutory requirement for SOLAS vessels to be able to display AIS targets on a screen merely a requirement to provide a simple alphanumeric Minimum Keyboard and Display (MKD). To meet the minimum requirements this display need show no more than three ships at any one time detailing bearing, range and name of ship. Therefore Class B users must understand that their vessel may not be appearing as a ‘bright beacon’ on the displays of the majority of SOLAS vessels. Although IMO requires all new radars fitted after 1 July 2008 to have good AIS display capabilities, existing radars will not have to be upgraded and so it will be many years before AIS data can be effectively used for navigation on many SOLAS vessels."​

 

[boatmike]

I agree entirely with PRV. It is going too far to say you will "almost certainly" not be seen. My point was you can't place a high reliance on being seen, especially in crowded waters. In mid channel or away from land you have a higher chance but SeeMe IMHO is more likely to ensure you are seen in most cases. Like most subjects on here there are opinions like the old men on the muppets. It's either "wonderful" or "rubbish". As with all things there are for's and against's. Fitting a transponder does no harm (apart from cluttering up everyone elses screen) but if you are fitting one to guarantee you will be seen you should think again.....

 

[prv]

If, by "ships" we are referring to commercial vessels over 300 tons or others with 12 or more passengers, with exeptions such as fishing or warships, then legally, according to the IMO recommendations and rules, they are obliged to have AIS transmit and recieve units. For receiver display the AIS system should have as a minimum a control panel in the form of a MKD (Minimum Keyboard Display).

Yes, we've already said all this (although the report from The Pilot is helpful, thanks).

In that particular post (only), I accidentally wrote "bridge" where I probably meant "radar" or "ECDIS". Of course all ships will have at least the useless MKD.

I'll edit the post.

Pete

 

[BrianH]

Fitting a transponder does no harm (apart from cluttering up everyone elses screen)

Screen "cluttering" is not so much the porblem, having to disable the CPA alarm because of it is, when Class A vessels are also in the same waters. Therefore, in my opinion it does do harm and for precious little advantage because, as we agree, there is a strong possibility of not being seen (by AIS target report) anyway.

 

[ukmctc]

I'm hoping to fit AIS during my health enforced refit to the boat; I can look up prices, but what is your real experience with relatively low cost AIS please ?

I aim to include a transponder and would like a decent ' Wacky Races ' they're there and you're here display screen.

I'm aware of the Standard Horizon VHF with AIS but really think the display too small and would like a transponder.

The NASA kit is not for me.

Any advice gratefully received,

Andy

Just fitted garmin 600i, excellent bit of kit can be used with or without radio or chart plotter.

 

[Rivers & creeks]

I think that's taking things a bit far. I read the MAIB report mentioned in YM this month about a radar-assisted collision between a yacht and a gas tanker on the east coast. It said that the gas tanker had AIS targets displayed on its radar screen, and the yacht would have showed up if she had had AIS transmit (which she did not). The tanker was built in 1997 so not brand new.

Many ships do display AIS on their radar or another primary graphical screen. The problem is that not all do.

Pete

When the "vast majority" don't meaningfully display AIS targets I reckon that means your AIS almost certainly won't be seen. Fit by all means but don't make any decisions based on the erroneous idea that your AIS signal has been seen. Because SeeMe virtually guarantees your visibility on any ship's display then that would appear to be a better buy. But SeeMe isn't sexy and isn't binary, AIS transponders are far more sexy and a quick VHF call to a mate on another yacht provides a binary confirmation that you are showing up on their plotter. And if your plotter screen is crowded with other yachts' AIS signal then it's a matter of pride for some people that their yacht is displayed as well.

 

[BrianH]

Yes, we've already said all this (although the report from The Pilot is helpful, thanks).
In that particular post (only), I accidentally wrote "bridge" where I probably meant "radar" or "ECDIS". Of course all ships will have at least the useless MKD.
I'll edit the post.

Sorry for the lecture on AIS basics, I genuinely thought you'd lost the plot ... although perhaps my darker ego saw the chance for some pedantic preaching. Never mind, it's an open forum and someone, somewhere, may have learned something.

What I find interesting, however, is that, in a somewhat long thread, nowhere has there been any post lambasting the use of the technology. In earlier days a thread on the subject would bring out a hard core of luddites critical of what they saw as reliance on electro-gimmickry and always invoking the tired old cliché of the Mk 1 eyeball - as if anyone using it didn't understand that any technology was merely an aid to basic seamanship. In fact, the only member I have ever put on 'ignore' was one such whose level of personal abuse was a direct response to my contributions on the subject. Could it be that the principle has at last gained acceptance, even among the die-hard purists?

 

[nimbusgb]

Just as a matter of interest a lot of these units ( digital yacht, comar and a few others ) share the same internals. The board is manufactured by one factory and OEM'd out.

 

[boatmike]

Doh! Read the thread before posting.... already said this !