"A" versus "B" AIS - worth transmitting?

[Dockhead]

Originally Posted by MartinR

Sorry, I want to argue the point. Driving ships has been my work for the last 30 years. Right now my work is 35000t displacement, so a medium sized cargo vessel.

Decision points for manoeuvres, depends a little, normally around 6 miles distance from other ships, more if meeting head on. In confined waters often much less. 10 miles, only when bored.

When meeting sailboats this is a little different. Firstly, sailboats are notoriously unreliable in keeping course, they tack and jibe and follow the wind. This is one of the reasons we do our manoeuvre quite late.

The other reason is much simpler. I need to see the sailboat optically or be able to plot it on Radar to plan my manoeuvre. Optically, the range for navigation lights on sailing yachts is some 2-3 miles. Daytime I can see the yacht about the same distance, unless really looking for it. Radar depends on the sea state, but often sailboats do not show up until some 2-5 miles out.

Then it takes a minute or so to come to a decision. So on average, I would say I change my course about 2 miles off in open waters. Less in confined waters, sometimes much less.

NEVER are collision avoidance decisions made by relying on AIS data. They often show wrong data/vectors. Plotting is ALWAYS done by ARPA, never by AIS, unless I can not get an echo. In this case I give you a very wide berth.

The big advantage about having an AIS on a sailing boat is that you will show up even in rough sea conditions or fog, making it easier to find you.

Well, different ships are run in different ways, and it is interesting and valuable to hear about how you run yours.


But that's not the way it's ever done, in my experience, around here -- speaking about 2 mile decision points. No sailor worth his salt would ever, for example, not ever ever, let you get within 2 miles of him with a small CPA -- I certainly wouldn't, at least not in open water. That is so close that your own maneuver will already have to be a very large alteration of course, to create a safe CPA. Some time before it got to that point, we will have maneuvered hard away from you.



Where I sail -- Channel, North Sea, Baltic, far North Atlantic -- it's 10 miles, as a rule. If there is traffic or other complicating factors, it might drag out to 4 or 5 miles, but never more than that. 4 miles is about the last point where you can change the CPA from something dangerous to something acceptable (at least 1 mile in open water, and standing orders in the North Sea often call for minimum 2 miles CPA) without a desperate hard rudder over maneuver. It's also the last point where you can count on the other vessel standing on -- something which is essential for reliability of your maneuver. By 4 miles out, all decent sailors are getting ready to abandon standing on and start their own maneuvers.



At 2 miles, the only sailboat still standing on will be some WAFI who never saw you, or who thinks he has the "right of way".

[rbrake]

Use what you have but remember Class A transmits at 12.5 Watts and Class B transmits at 2 Watts. The Ship you see at 18mi may not see you until 3 miles or less. AIS is the best thing since sliced bread but it doesn't remove the need for a proper watch.

[Pieta]

Having experience on both commercial vessels and sailing yachts I find AIS class B reception unreliable at least and we have upgrading of our class B transmitter high on our priority list.

[Jhhastie]

A lot of good info. Another fact is that if you are cruising offshore, Class A AIS will transmit a. Lot further. This
means if a ship is going fast, you may be seen sooner if on a collision course. Also, ignore the comments about AIS receivers. If you see a potential collision course because of your AIS you can hail the ship by radio to confirm their sighting you. Remember, not all us have radar.

[AlanWilson]

Definitely worth transmitting; B (not A, which is big ships). In some countries' waters an AIS transmitter is mandatory on all boats other than rowing boats etc, eg Iceland (where the coastguard radioed me to say my AIS transmitter was faulty since they saw me on radar but not on AIS). Around Norway an AIS transmitter is assumed on all boats and seems to be used for collision avoidance more than radar (I can testify to this!).

[Recy]

Originally Posted by Pieta

Having experience on both commercial vessels and sailing yachts I find AIS class B reception unreliable at least and we have upgrading of our class B transmitter high on our priority list.

Is there any reason that a B-receiver generally not should be as good as an A- receiver or could that vary with different brands. When receiving.

[svmobert]

Originally Posted by Recy

Is there any reason that a B-receiver generally not should be as good as an A- receiver or could that vary with different brands. When receiving.

There aren't Class A vs Class B receivers. There are just receivers that receive both types. The reliability of Class A vs Class B rely on the transmitter side.. Class A has higher power and more often reporting. But Class B is really good enough for leisure vessels, and even a Class B Transponder will receive Class A targets a long ways off. We were seeing commercial ships (Class A) 110 miles away one day on our Class B AIS.

[Recy]

[QUOTE=Sea-TechSystems;2785815]There aren't Class A vs Class B receivers. There are just receivers that receive both types.

Yes I know that so what meant was: Is an A-transponder receiving better than a B-transponder.

[CarlF]

CSY-mans evidently doesn't have AIS. Hailing "Container Ship" this is "Little sailboat" has never gotten a response for obvious reasons.

It's my experience that ships do generally answer a hail that includes their name and the name of a vessel they can see on their AIS display.

Nor do they resist making a minor course change if the CPA is going to be a bit tight.

[GrowleyMonster]

Originally Posted by Cpt Pat

Yes, yet another lawyer. In the real world, with real cargo ships floating around nearby, it helps to let them know you have a navigational issue. We are not in a courtroom. The legal status of an AIS nav status is not my concern. Not getting run over is.


I'm not surprised if your academy didn't teach you anything about traffic considerations regarding sailing vessels. Many think all boats get around with engines.


This is straight off the USCG site:

Rule 3

• The term "vessel restricted in her ability to maneuver" means a vessel which from the nature of her work is restricted in her ability to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel. The term [Int] "vessels restricted in their ability to maneuver" shall [Int] include but not be limited to:
  • A vessel engaged in laying, servicing, or picking up a navigational mark, submarine cable or pipeline;
  • A vessel engaged in dredging, surveying or underwater operations;
  • A vessel engaged in replenishment or transferring persons, provisions or cargo while underway;
  • A vessel engaged in the launching or recovery of aircraft;
  • A vessel engaged in mine clearance operations;
  • A vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course.
  https://navcen.uscg.gov/?pageName=def3g_RAM
  

Those are just example situations. Notice the wording: "...shall include but not be limited to."


Read more closely the next time.

RAM status is entirely at the captain's discretion. THERE ARE NO LIMITATIONS! Didn't your academy teach you that?

If I am only able to sail a limited range of headings because of sea state, those conditions have restricted my ability to maneuver.

Wow! Everyone's an expert and I suppose they're all mad about spending Saturday night at their keyboard - so they all want an argument. Call your Coast Guard and ask them. If you don't like the rules, write your congressman. I'm not here to give navigation lessons. Not my job.

But what does any of this have to do with the topic of the thread? Start a new thread.


Post all the legalistic lawyer-ly challenges you want. I am now ignoring this thread. I came here to answer the OP, not to jump into a den of trolls. I've wasted too much of my time answering you people.

Don't be silly. First of all, in the example you give, (bolded by me) it is not the nature of the vessel's work that is restricting ability to maneuver, but sea conditions. This is NOT RAM. Plus, it has to be incredibly tough conditions that will not permit you to turn to give way to a vessel if required. I would have to ask why you were there in the first place. What work is a sailing yacht doing, anyway? None, apart from making a passage. Not the intent of the rule to cover this at all. NUC comes closer to covering this, and you had better be transmitting securite messages if you are claiming NUC status, too.


Captain's discretion? EVERYTHING is at the captain's discretion. That doesn't mean he won't have to answer for his discretion or indiscretion at some point. Making bonehead decisions, particularly contrary to The Rules or other laws or regulations, or contrary to ordinary rules of good seamanship, is not excused by having Master's authority.


By the way, if you HAVE an engine and simply refuse to use it when safety or simple good seamanship require it, you could have some explaining to do about that if there is any sort of mishap that the CG is compelled to take an interest in.

[Nicholson58]

We love our Vesper Watchmate 850 class B. We use AIS for all of the usual reasons but also to locate friends in a large anchorage and for anchor watch. Ours is stand alone so no othe devices need be on for it to run. It has saved our bacon a couple of times in the eastern Caribbean by identifying a tug & tow at night. We would have ducked behind the tug except for the added information. The tow was 1500 meters behind and not lighted.

[Cpt Pat]

Originally Posted by GrowleyMonster

Don't be silly. First of all, in the example you give, (bolded by me) it is not the nature of the vessel's work that is restricting ability to maneuver, but sea conditions. This is NOT RAM.

Growley indeed!

The true sign of someone who loves gratuitous argumentation is when they argue with someone who has AGEED with them.

Read the thread and see my post #85: http://www.cruisersforum.com/forums/...-211386-6.html


"I am appropriately informed, and though that was the USCG advice to me, I won't use RAM. OK."

[Cpt Pat]

Originally Posted by Nicholson58

We love our Vesper Watchmate 850 class B. We use AIS for all of the usual reasons but also to locate friends in a large anchorage and for anchor watch. Ours is stand alone so no othe devices need be on for it to run. It has saved our bacon a couple of times in the eastern Caribbean by identifying a tug & tow at night. We would have ducked behind the tug except for the added information. The tow was 1500 meters behind and not lighted.

I have one of the older, now discontinued, Vesper Marine displays. I swear by its ability to declutter irrelevant traffic. My chartplotter (Standard Horizon) would produced many false alarms on vessels that would enter the CPA radius but were not underway or sailing away from my vessel.

[tanglewood]

Re A vs B power levels, something said earlier bears repeating. Antenna height, and quality of installation will have WAY more impact on your ability to see and be seen, than the power difference between A & B. Like with radar, the horizon will get you way before the power runs out.

[Dauntlessny]

Originally Posted by AedanC

We transmit class B and I’ve seen enough big ships alter course to avoid us that I’m happy we are visible. It’s definitely not a waste of money.

Exactly my experience also.
When I had receive only, I always had to change couse.
Since i got AIS Transceiver 5 years ago, ships consistently stay 3 to 5 nm away.