AIS thread drift.

[Star-Lord]

My position is that it should be maritime law (mandatory) for all vessels travelling at night (or in fog) to be fitted with AIS and turned on (class B transponder in the case of recreational vessels).

There is no law saying you must have AIS - so if you have not got AIS - then you have not got it! If you do not want it - then do not get it. I have it because imho why on earth not. I would also highly recommend it.

There are a few good reasons not to switch on your AIS. For example - if you are in Pirate infested waters - or if you are engaged in a smuggling operation - or if you do not want your annoying neighbour to know you have left the anchorage / marina and are moving around the corner.

There is also one obvious reason not to buy AIS and that is cost. Budgets are budgets.

Roberto... SOTDMA has been googled and it look like a useful upgrade! There have been loads of times a target I am tracking disappears! Or the AIS signal is dodgy. Maybe 5% of the time maybe more. But that has always been tracking from a distance. When it matters it has always worked for me. Being able to see if a target is going to get too close for comfort, or collide, well in advance is very useful.

One of my favourite features is seeing the helicopter icon wiz across the chart plotter ( I presume they are coast guard ?). If you are quick enough you can see how fast they are travelling!

 

[Roberto]

One of my favourite features is seeing the helicopter icon wiz across the chart plotter ( I presume they are coast guard ?). If you are quick enough you can see how fast they are travelling!

And they are "visible" from really afar

they appear to follow TSS rules too /)

 

[Star-Lord]

And they are "visible" from really afar

they appear to follow TSS rules too /)

I have never seen planes before! Yes they are seen from afar...

 

[doug748]

Talking about Galicia Round Finisterre/Camarinas area, a lot of Class A transmitters probably over 50-60, my Class B (non SOTDMA) and other class B could not find a slot to transmit during several minutes.
I have both a transponder and a receiver-only AIS machines; totally separated.
Screen copy of my last available transmission (green target) as made possibly 3-4 minutes earlier, together with my actual (red target) position. One could see the transmission delay of the green target only by clicking over it, opening the description window and reading the "position received xxx sec ago" data, which I doubt people do every time they look at a target, I would not want others to believe I am in the green location while I am in the red one instead.
I made a huge number of checks by myself and also crosschecks with other fellow boaters transponders, same occasional delay effects for anyone, significant enough for me to decide to turn off my AIS transmissions when there are more than 40-50 Class A. Don't want to convince anyone, but I won't be convinced to do any different, at least until I get a SOTDMA transponder

I guess with a crummy aerial on the pushpit, like mine, that only picks up targets at 10 miles, then the unit will find no problem in getting a slot?

If so, it's an uplifting bonus for slack characters who rub along with basic kit. I was always baffled by the interest in picking up AIS data at extreme range.

PS
I also have a transponder + receiver and have never noticed the AIS image much out of sync with my plotted position.

.

 

[Sandy]

AIS makes life easy for everyone. It also saves lives and time and money... all these points have been pointed out to you very reasonably in this thread.
Instead of engaging in debate you are huffing and puffing about monsters at night! What a Joker ?

How does it save money?

 

[LadyInBed]

I expect sometime in the not very distant future. AIS May become a requirement for pleasure vessels.

I think the problem with that possibility would be screen clutter and the way all the transmissions are multiplexed.

 

[lw395]

I guess with a crummy aerial on the pushpit, like mine, that only picks up targets at 10 miles, then the unit will find no problem in getting a slot?
...

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And ships with decent aerials will have no trouble shouting it down....

 

[Star-Lord]

How does it save money?

Page 3 'Daydream believer' posts an example of saving money... 'Now if I had not got AIS one might wonder if they would have had to send the lifeboat to go & look.'

 

[Star-Lord]

I guess with a crummy aerial on the pushpit, like mine, that only picks up targets at 10 miles, then the unit will find no problem in getting a slot?

If so, it's an uplifting bonus for slack characters who rub along with basic kit. I was always baffled by the interest in picking up AIS data at extreme range.

PS
I also have a transponder + receiver and have never noticed the AIS image much out of sync with my plotted position.

.

A quick 'Yacht AIS range" Google revealed ...

'20 nautical miles' What is the typical range of the AIS? Normally, an AIS-Receiving station using an external antenna placed 15 metres above sea level, will receive AIS information from AIS-equipped vessels that sail within a range of 15-20 nautical miles around it.'

10nm is about what I get on a consistent basis.

 

[johnalison]

My rather rough estimation of AIS range is about half as long again as the useful VHF range. In open sea conditions I would be disappointed not to see ships at 20 miles with my masthead aerial and regularly get twice this in summer conditions.

 

[doug748]

My rather rough estimation of AIS range is about half as long again as the useful VHF range. In open sea conditions I would be disappointed not to see ships at 20 miles with my masthead aerial and regularly get twice this in summer conditions.

Indeed but the more ships you see, the more difficulty the set has in finding a gap for your AIS transmission; perhaps. Roberto has reported a worrying lag with up to 60 ships in range. In post 60.

I was just suggesting that a less efficient aerial might be an advantage in this situation. No sure it is, just suggesting it.

 

[jdc]

My position is that it should be maritime law (mandatory) for all vessels travelling at night (or in fog) to be fitted with AIS and turned on...

Although I'm an enthusiast for AIS Tx. I wouldn't make anything mandatory, from wearing knickers to flying a recognised ensign. On second thoughts, maybe keeping some sort of look-out...

 

[jdc]

AIS range. As so often when these technical questions pop up, why not look at the CA's pages on the subject? https://www.theca.org.uk/system/files/VHF_and_AIS_Range.pdf for a detailed analysis. The range varies according to case (antenna height, class A or B etc).
Can't see the link - well, join the CA.

 

[Star-Lord]

Can't see the link - well, join the CA.

You seem to think joining the CA is mandatory!

 

[Roberto]

I guess with a crummy aerial on the pushpit, like mine, that only picks up targets at 10 miles, then the unit will find no problem in getting a slot?

Hello doug,
thanks for your consideration.
I tried swapping a few times the input into the PC/OpenCPN from 1.my receiver only (masthead antenna, SH2100 combined VHF/AIS receiver), to 2.my transponder (antenna on the stern gantry, about 4m asl), the lower antenna loses only the signal from the farthest ships, meaning tens of miles away.

While I am personally convinced about the effect of many class A against class B transmissions, I have also concerns about Class B vs Class B. Example here, during summer Quiberon bay (a roughly 15x15 naut miles area) has such a number of AIS class B transmitting boats that as you approach one marina, the AIS display shows you another boat ahead of you, then the same boat suddenly jumps behind, then according to the display you are running over it.
This is without a lot of class A, so maybe some classB transmitters "wait" for their slot also when other classB are transmitting? I have no answer, surely the effect is occasionally one's own target is seen by others as being very different from the actual position.
I think the Solent might be similar in terms of crowding, should anyone want to make some tests we might have more examples to understand how these things work in reality: pick a day with a lot of transponders, sail with a couple of friends and get in touch to check what is the "last received data" each others have.
rgds r

 

[Daydream believer]

I wouldn't make anything mandatory, from wearing knickers to flying a recognised ensign.

Do you go to foreign shores much?

 

[Momac]

I have found AIS a very useful tool , even occasionally allowing me to see ships that are just around the corner of the river and would be invisible by any other means.
On open water I have spotted craft that are barely visible or not yet in view and made small course adjustments.
Moving near and among moored and anchored ships it helps identify those that are anchored or just starting to move. In the haze it can be difficult to judge which way a slow moving ship is going and AIS can clarify that.

For me the AIS is a good non verbal form of communication and its mostly about not getting in the way of ships and not getting anywhere near fishing boats .

In an emergency AIS transmission might help guide the rescue to you ..... or might guide you to assist another boat. That's a possibility that is rarely mentioned .

Other than reported possible screen clutter in some very busy areas I don't see any negatives .

I do wonder why some old school navigators refuse to use technology . It seems to me not wanting to be informed and not wanting to communicate lacks consideration of others .

 

[capnsensible]

From what Im reading here, I dont think anyone is refusing to use technology. AIS is without doubt a great tool.

The misconception, I reckon, is that everyone has got it and everyone uses it.

What is being pointed out is an over reliance on it. From what Ive seen, the further away you get from the busy leisure vessel areas in N. Europe, the less likely a vessel is to have it. Not only that, there is an assumption that every poster has a boat and will fit it. What about all the charter yachts buzzing around? What about all those that sail on others boats that dont have it fitted? I got a couple of friends I take out most weeks with no AIS. Am I worried? Of course not.

You dont have to be 'old school' to learn how to use judgement of distances, angles and how to use a hand bearing compass. All the experienced navigators and skippers are saying is dont put all yer eggs in one basket. Like most parts of sailing.

 

[Momac]

From what Im reading here, I dont think anyone is refusing to use technology. AIS is without doubt a great tool.
.....................dont put all yer eggs in one basket. ...........

I agree .

However one poster did strongly object to the suggestion of mandatory AIS and indicated he is not even tempted to listen on his vhf

 

[RupertW]

I agree .

However one poster did strongly object to the suggestion of mandatory AIS and indicated he is not even tempted to listen on his vhf

A lot of us strongly object to the word mandatory as it usually comes from the most insecure boaters on the forum, or those whose philosophy of boating is a million miles away from those who want to get away from jobsworths and rule makers.

I personally have no objection or need for AIS or radar, but understand those who make different choices. I won’t take intolerance to us being able to make our own choices, though. And if the defence is “the dark is harder than the light” then I despair.

I can’t defend my non-VHF use so easily but don’t like the chatter on other people’s boats when they have it on, especially if I’m off-watch. It was no part of my first 20 years sailing and the set rarely gets used even booking berths as mobiles are often easier and with effectively a far longer range if you are a few hours away along a coast. But I accept I’m open for valid criticism for that choice.