AIS Question

[Jean]

Planning fitting a class B AIS receiver to a small leisure yacht used by more than one skipper. Had intended going for a full class B transponder, but now advised that commercial vessels using class A do not necessarily have to monitor AIS class B signals, and thus likely perhaps to get a false sense of security with the class B transponder. Would appreciate comments from any commercial operators on here.

 

[homa]

AIS

All I can say is buy the best you can afford

We use AIS a lot (N. Sea ferry) on our radars and Chart plotters

We don't rely on it but we do pick up all AIS targets. As I understand it, class B transmit less frequently so in busy waters you may find the class B being picked up at a lower range and less frequently.

We do find when approaching Rotterdam that our AIS display gets overloaded and will prioritise the nearest targets. in practice this means targets say 5 miles away don't even get picked up, so we still rely on mark one eye ball and radar.

I sail for both pleasure and I earn a living in the commercial sector, and I can't decided between an active radar transponder or AIS transmitter for my own yacht. My gut instinct is to go for the radar transponder first and AIS second. If only the radar transponders were cheaper I'd have bought one years ago.

Just a word of caution here, we "commercial boys" don't watch the AIS display all the time and we do find a number of spurious "ghost" AIS targets from time to time, so confidence in AIS is not 100%. But we do generally watch the radar, as we use that for navigation and collision avoidance ALL the time. Not all radars even in the commercial sector receive AIS information .....yet.

 

[farmerdenne]

AIS

I work on tankers deep sea and have experience with AIS.

My info tells me that Type B will only be picked up if there is space enough on the AIS. So if my AIS has 200 "slots" for ships and 200 type A ships were in range of my AIS, your B type AIS would not show up. Even if you were 10 meters away.

Type A is better as you will show up on Ships equipment and you are therefore also being recorded into it's "black box". So should a close quarters situation or collision arise, it would have been recorded.

If you can afford Type A get it.

I hope that makes sense. If not let me know and I will try explain another way.

Happy and safe sailing!

 

[maby]

Hmmm, I'm disturbed that you need to "notice" an AIS target - my assumption was that the electronics would do the calculations and sound an alarm if another boat would come too close for comfort assuming you both remained on the same course...

 

[farmerdenne]

The electronics do indeed do a calculation, and a calculated CPA (Closest Point of Approach) for each vessel is often displayed. However, alarm parameters are in most cases set by the user. i.e. The unit can be set up, by the user, to only alarm if the CPA is lower than 0.5 of a mile or even not at all.

The AIS system should not be depended upon as collision avoidance tool. As a variety of the inputs into the unit are manual, and also due to the issue that you are using other vessels inputs (speed and course even GPS posn.) which are not always accurate. In my experience I have noticed ships on AIS headings 090 degrees different from their actual heads.


Most units take head and speed from GPS, is all well and good however, if you are in a tidal area the ships head and speed over the ground will differ from its speed and head through the water.

Once again do get the best one you can and I would advise on an A Type. But it should not be depended upon for collision avoidance.

Not sure what other commercial guys might say but I believe this to be all correct. An interesting subject especially due to the supposed AIS 'assisted' collisions.

 

[maby]

Well, I fully appreciate that you should not rely on AIS for collision avoidence, any more than you should rely on a chart plotter for navigation, but both are expensive items and they need to contribute something towards safety if they are to justify their existence! I would have hoped that they would normally be configured with a CPA alarm of no less than a hundred yards - though I suppose that even set that close in, it would be going off all the time in most ports...

 

[nigel1]

Well, I fully appreciate that you should not rely on AIS for collision avoidence, any more than you should rely on a chart plotter for navigation, but both are expensive items and they need to contribute something towards safety if they are to justify their existence! I would have hoped that they would normally be configured with a CPA alarm of no less than a hundred yards - though I suppose that even set that close in, it would be going off all the time in most ports...

Yep, your right, deep sea, we set the alarm to a realistic level, close to port, its normally disabled, too many alarms sounding and distractions.
I'm a skipper on an anchor handling tug, we're in the Baltic at the moment, and running anchors for a pipe lay barge. AIS alarm is disabled, as we are frequently heading directly towards another vessel, or working within a couple of meters of one.

Be aware that Class A units can be set to filter out Class B, but as far as I am aware, if a CPA alarm has been set, a Class B target meeting those limits will sound an alarm, and will pop up on the screen. If Class B targets are filtrered out, then the system assigns them as passive targets and they are not displayed, unless meeting CPA limit

 

[maby]

That all makes sense, Nigel.

Ideally, the AIS gear should be able to recognise that the ship has been on a reasonably steady course at a decent speed for more than half an hour and re-enable the alarm automatically on the basis that it must be out of port!

 

[farmerdenne]

Well, I fully appreciate that you should not rely on AIS for collision avoidence, any more than you should rely on a chart plotter for navigation, but both are expensive items and they need to contribute something towards safety if they are to justify their existence! I would have hoped that they would normally be configured with a CPA alarm of no less than a hundred yards - though I suppose that even set that close in, it would be going off all the time in most ports...

AIS was not introduced for safety, it was for security after the 911 incident. it was around July 2004 it became compulsory for ships over 500gt to carry.

Working on ship with lengths of 330 meters having a min CPA setting of 100 meters would be no help as we would have the potential to hit the remaining 230 meters of ship! But yes, they should have a min CPA setting. And ought to notify the operator of close quarter situations developing.

More and more modern ships are using integrated electric charts and AIS. So AIS 'targets' are displayed along with radar images onto the charts. Giving better awareness to the operator.

 

[AntarcticPilot]

Once again do get the best one you can and I would advise on an A Type. But it should not be depended upon for collision avoidance.

It was my understanding that small craft weren't allowed to use class A - that's why class B exists. After all, if every yacht in the Solent started transmitting class A AIS signals, then AIS equipment would rapidly become useless as it would be swamped!

However, I may well be wrong; perhaps someone can elaborate on this?

 

[nigel1]

I'm 99.9% sure your right about this, small craft are not permitted to use Class A transceivers, it would be chaos otherwise. I'll try and find the correct regulation, or get one of the apprentices to find out

Just to clarify what I wrote earlier about filtering Class B. On a vessel required to fit and use Class A, the AIS base unit itself does not filter out Class B. IMO requirments are that for new equipment, the radar must display AIS targets, and in vessels fitted with such radars, (and also ECDIS), the radar or ECDIS is used to display AIS information. It is the radar which can be used to apply the filters.
With more and more Class B transceivers being used, it may reach a stage that the IMO will allow the AIS base unit to filter out Class B just to avoid clutter.

Going back to small boats using Class A, if they did, thet would need to have heading input and a rate of turn input as well, and it must transmit on a much higher power level. These alone would preclude most small boats from using Class A

Regarding use of Class A on samll craft, this is the best I could find so far

www.dft.gov.uk/mca/lrgtxt/min_199-2.pdf

 

[AntarcticPilot]

I'm 99.9% sure your right about this, small craft are not permitted to use Class A transceivers, it would be chaos otherwise. I'll try and find the correct regulation, or get one of the apprentices to find out

Just to clarify what I wrote earlier about filtering Class B. On a vessel required to fit and use Class A, the AIS base unit itself does not filter out Class B. IMO requirments are that for new equipment, the radar must display AIS targets, and in vessels fitted with such radars, (and also ECDIS), the radar or ECDIS is used to display AIS information. It is the radar which can be used to apply the filters.
With more and more Class B transceivers being used, it may reach a stage that the IMO will allow the AIS base unit to filter out Class B just to avoid clutter.

Going back to small boats using Class A, if they did, thet would need to have heading input and a rate of turn input as well, and it must transmit on a much higher power level. These alone would preclude most small boats from using Class A

Regarding use of Class A on samll craft, this is the best I could find so far

www.dft.gov.uk/mca/lrgtxt/min_199-2.pdf

Thanks; I note that this document doesn't actually prohibit the use of class A by small craft; it just points out the technical problems of implementing it! And these days, increasing numbers of small craft DO have heading devices (electronic flux-gate compasses) that are linked into the equipment set-up. A bigger concern is the use of type-approved GPS; the small craft market moves pretty quickly, and type-approval to commercial standards isn't going to happen for equipment marketed in that field.

Of course, the power requirements for Class A would rule it out for most sailing craft, but a power boat would have no problems with it.

 

[nigel1]

Thanks; I note that this document doesn't actually prohibit the use of class A by small craft; it just points out the technical problems of implementing it! And these days, increasing numbers of small craft DO have heading devices (electronic flux-gate compasses) that are linked into the equipment set-up. A bigger concern is the use of type-approved GPS; the small craft market moves pretty quickly, and type-approval to commercial standards isn't going to happen for equipment marketed in that field.

Of course, the power requirements for Class A would rule it out for most sailing craft, but a power boat would have no problems with it.

Yes, type approval will make it expensive, it's not just the eqwuipment thast needs to be approved, but the whole installation, a flux compass for sure will not cut it, it will need a proper gyro, and rate of turn indicators are noit cheap either, you'd be looking at a massive bill for a proper and approved install

 

[philip_stevens]

a flux compass for sure will not cut it, it will need a proper gyro,

A small commercial vessel I electrically maintain, has had a Furuno GPS compass fitted to allow autopilot use.

A fluxgate compass "may" have sufficed, but the vessel is steel, and the GPS compass was preferable to a gyro.

So long as the authorities don't play around with GPS, then this will be OK. It has turned out to be very accurate and stable.

 

[nigel1]

A small commercial vessel I electrically maintain, has had a Furuno GPS compass fitted to allow autopilot use.

A fluxgate compass "may" have sufficed, but the vessel is steel, and the GPS compass was preferable to a gyro.

So long as the authorities don't play around with GPS, then this will be OK. It has turned out to be very accurate and stable.

They are a good bit of kit, we have one on my "working" boat which is in addition to the two gyro's we have. Approved by DNV, Lloyds etc for use with Dynamic Positioning.
One we have costs about £3000, but I guess they'll come down in price as more vessels start to use them. No moving parts or service required.

 

[wadget]

AIS was not introduced for safety, it was for security after the 911 incident. it was around July 2004 it became compulsory for ships over 500gt to carry.

Working on ship with lengths of 330 meters having a min CPA setting of 100 meters would be no help as we would have the potential to hit the remaining 230 meters of ship! But yes, they should have a min CPA setting. And ought to notify the operator of close quarter situations developing.

More and more modern ships are using integrated electric charts and AIS. So AIS 'targets' are displayed along with radar images onto the charts. Giving better awareness to the operator.

It was actually the braer inncident in Shetland that caused the Introduction of AIS just these things take a long time to come into force. But you were right it had nothing to do with navigation, just knowing which ships were where.

 

[lfreddecolo]

Once again do get the best one you can and I would advise on an A Type. But it should not be depended upon for collision avoidance or get one of the apprentices to find out Just to clarify what I wrote earlier about filtering Class B. On a vessel required to fit and use Class A, the AIS base unit itself does not filter out Class B.

 

[watermint]

i got a nassa ais and i can run it on ( A and B ) on my yacht but i leeve it swich on both leest u get seen out ther on the hi sea

 

[ukmctc]

remember nothing beats a good watch crew and a sober skipper or the AIS doesn't work! see Carrickfergus 7th March 2012 Ferry and Cargo ship collide in Belfast Loaugh.

 

[joe_bowry]

Plymouth University Research into AIS transponders on small vessels

Do you use a boat on the River Medway?

If you do, please take a few minutes to complete this survey which looks at the use of AIS and the safety of small vessels on the River Medway.

The thesis will contribute towards obtaining a Bachelor of Science Degree with Honours in Navigation and Maritime Science from the University of Plymouth.

Please be assured that all participants are free to withdraw from the research at any stage and ask for their contribution to be destroyed if he/she wishes. Anonymity is guaranteed.

Thank you.

http://www.surveymonkey.com/s/KYHZT3R