New price point for AIS class B+

[Tillsbury]

Originally Posted by Dockhead

SOTDMA AIS ("B+") has profound advantages over the older type ("B"). The messages get priority in the same way as Class A and are far less likely to be dropped. The difference in cost is really worth it. The obsolete Class B units are cheap only because they are -- obsolete.

Agreed, technically the system is much better. However, no-one has yet explained how this would be useful to the small boat sailor.

[Pete7]

Originally Posted by Dockhead

SOTDMA AIS ("B+") has profound advantages over the older type ("B"). The messages get priority in the same way as Class A and are far less likely to be dropped. The difference in cost is really worth it. The obsolete Class B units are cheap only because they are -- obsolete.

The cost to swop from B to B+ likely £300, taking into account the re-sale value of the B.

Hence the question, is it a problem that warrants spending another £300? given that there are other boat projects vying for those precious boat bucks. The answer of course is it depends on the individual and the perceived benefits. Are B class transmissions consistently being dropped so a vessel never transmits or perhaps just occasionally, who knows?

Cpt Pat, useful thanks

[Cpt Pat]

...and you should never trust your life to any software-dependent navigation device. Keep one eye on the sea when using AIS.


It is my acquired professional opinion that all software developers are adderall-addicted myopically-focused over-caffeinated blithering idiots. It's my job to clean up their messes.

[Marathon1150]

Originally Posted by Brian.D

I am sure I am stating the obvious, but AIS is only good if the other vessel is also using AIS. I think radar is a better choice because you can see a vessel (if big enough or uses a radar reflector) even in adverse conditions. JMHO

Absolutely agree!

Crossing from Mexico to French Poly (a 29 day passage to Nuku Hiva) we encountered several large ships (tankers and freighters more than 1000' long) that we knew about because of a 10nm range warning on our AIS. Knowing the closest point of approach was very useful as well because if it was going to be less than a few miles we radioed them using their broadcast MMSI number to discuss the situation. In the three or four instances where this happened, we offered to change our course and in every case the captain of the ship told us to hold steady and they would alter their course.

However, we also came across several very large fishing vessels that we detected visually at night who were not broadcasting via AIS. Fortunately they were as well lit up as the oil platforms off of California and easy to see.

In any case I still believe that AIS is an important piece of safety equipment despite not being compulsory on a pleasure craft the size of our humble little vessel. And, the AIS screen is an interesting source of entertainment on long night watches if and when something shows up

We had a nice chat with the captain of this vessel, the first to alter course for us because of the proximity of our course to his. We knew about him, and he about us, because AIS told us about its location relative to ours, long before we would have detected the ship with radar and using significantly less power to do so.



And for consistency with the thread of this discussion, I do not think that B+ would be worth the investment in conditions like this. One ship in 3 or 4 days does not require the transmission sophistication or range of B+ compared to B.

[Paul L]

I see a lot of references to AIS not being compulsory for small vessels, this is not true for a lot of cruising boats. Many countries in SE Asia require AIS for foreign boats to clear in. Indonesia, Singapore, Malaysia, Thailand all require it.

[Simi 60]

Originally Posted by Paul L

I see a lot of references to AIS not being compulsory for small vessels, this is not true for a lot of cruising boats. Many countries in SE Asia require AIS for foreign boats to clear in. Indonesia, Singapore, Malaysia, Thailand all require it.

That's 4 countries in a vast world.
And as you pointed out, they only require the handful of foreigners and not the thousands of locals to have it.

[Paul L]

Originally Posted by Simi 60

That's 4 countries in a vast world.
And as you pointed out, they only require the handful of foreigners and not the thousands of locals to have it.

And this is a cruisers forum with many cruisers preparing their boats to travel long distance, so I thought it appropriate to point out. If the fact doesn't fit into your cruising view, just ignore it.

[Dockhead]

Originally Posted by Tillsbury

Agreed, technically the system is much better. However, no-one has yet explained how this would be useful to the small boat sailor.

It should be self-evident that having your vessel show up reliably and constantly on the screens of ships, rather than dropping off from time to time and moving erratically, is useful to the small boat sailor, and his safety.

[Dockhead]

Originally Posted by Pete7

The cost to swop from B to B+ likely £300, taking into account the re-sale value of the B.

Hence the question, is it a problem that warrants spending another £300? given that there are other boat projects vying for those precious boat bucks. The answer of course is it depends on the individual and the perceived benefits. Are B class transmissions consistently being dropped so a vessel never transmits or perhaps just occasionally, who knows?

Cpt Pat, useful thanks

I think it's a fair question and the answer depends on your budget and how much traffic you sail in.


People who sail close to shore and encounter very little traffic will not have much need for it.


But TDMA Class B does drop out, especially in busy water with lots of vessels transmitting. It does show your vessel moving erratically sometimes. So it might very well be worthwhile for those of us who sail a lot in traffic. YMMV.

[Hoodsail]

I don't have radar so when encountering fog (3 for 3 now) off Block Island heading west toward the long island sound, my Vesper AIS B transponder gave me a bit more confidence in that the high speed ferries would "see" me and importantly me them. Albeit my 5-6 knots was much inferior to their 20+ knots for collision avoidance.

[Tillsbury]

Originally Posted by Dockhead

It should be self-evident that having your vessel show up reliably and constantly on the screens of ships, rather than dropping off from time to time and moving erratically, is useful to the small boat sailor, and his safety.

That's assuming that a big ship is both watching on AIS while in a very busy channel (rather than ARPA), and that you are intending to go anywhere near it. Or indeed it's even taking the slightest bit of notice since it'll be in a channel and be standing on even it does bother to take notice of you.

At sea when a big ship has any inclination to adjust its course for you, a class B is going to show you up fine.

[Dockhead]

Originally Posted by Tillsbury

That's assuming that a big ship is both watching on AIS while in a very busy channel (rather than ARPA), and that you are intending to go anywhere near it. Or indeed it's even taking the slightest bit of notice since it'll be in a channel and be standing on even it does bother to take notice of you.

At sea when a big ship has any inclination to adjust its course for you, a class B is going to show you up fine.

In heavy traffic, like English Channel, North Sea, Elbe Approaches, where I sail, you cannot avoid getting into risk of collision situations with multiple ships at once, on a regular basis. If your AIS signals don't get through reliably, this will increase the risk that you won't be seen or a wrong decision will be made. Enough to matter? It's up to everyone to decide. Until recently we didn't even have a choice, so there was nothing to think about.


Small plastic sailboats show up poorly on radar, even big ship radar, and MOST radar reflectors are basically useless (see the test some years ago in PBO). So you really don't want to count on ARPA, for ships to see and evaluate risk of collision situations with you.


If you are never in heavy traffic, then, as I said, you will not care much, but different waters have wildly different conditions, so YMMV.

[Dockhead]

Originally Posted by Hoodsail

I don't have radar so when encountering fog (3 for 3 now) off Block Island heading west toward the long island sound, my Vesper AIS B transponder gave me a bit more confidence in that the high speed ferries would "see" me and importantly me them. Albeit my 5-6 knots was much inferior to their 20+ knots for collision avoidance.

Sailing in fog, without radar?

[mikedefieslife]

Originally Posted by Pete7

Just shy of double for Em Trak in the UK last October when we were shopping.



Indeed. Whilst it might only be £350 for the B, or £650 for B+, it isn't just £300 because there is a fairly good chance the installation is part of a bigger project and most of us have limits.

I suppose the question is if the output watts don't make any real difference, then only possible shortfall is the limit of 2000 AIS units wanting to transmit in small area. So how often does that happen?

Pete

Less than £120 between an Em-trak with B and one with B+

Mine was even cheaper as it was shipped to the canaries so tax free.

What are these installation costs you talk of? Mine is attached via some 3m dual-lock which I already had, some 4mm2 wire which I already had on board, and an antenna which was already wired and mounted as a back up anyway.

[mikedefieslife]

Originally Posted by Dockhead

....
Small plastic sailboats show up poorly on radar, even big ship radar, and MOST radar reflectors are basically useless (see the test some years ago in PBO). So you really don't want to count on ARPA, for ships to see and evaluate risk of collision situations with you.

....

Is that really true though? Most of use with 3/4g radars can happily pick up 5m fishing boats and other small pleasure craft.

In bad weather the result might be different, but then that is exactly the type of weather these small craft won't want to be around in.