Class B makes you that confident?

[macd]

Echomax RTE, X-band only, £360 new on ebay

Same prices from Cactus: http://www.cactusnav.com/echomax-active-radar-reflector-p-10988.html

 

[johnalison]

I don't see it that way. Isn't it more a case of spending effectively? A Class B transponder is £450 - the same as a Sea-Me or Echomax Active radar reflector. The difference is that the active radar reflector always works to enhance your visibility on ship radars, whereas the transponder might, or might not, depending on whether the ship is filtering out Class B clutter. It's a no-brainer.

I think Roger knows that I was just doing a little bit of digging. If I had to choose between the security of an active reflector and an AIS receiver, I would certainly have a problem but between a reflector and class B, it would be reflector every time.

I overcome the alarm problem by the bizarre method of turning the alarm off. This does mean that I have to view the screen occasionally.

 

[Scotty_Tradewind]

I've always been concerned about the ability of others to 'see' me, especially at night and in fog.

So, it really comes down to me avoiding 'them'.

I fitted a dual band active radar reflector soon after having my present boat.

With my own radar and AIS receiver, I guess I'm pretty well satisfied that I if a good look-out is on watch and that all other possible

navigation precautions have been taken, then there is not a lot more that a small yacht like mine can take.

S.

 

[BrianH]

Sadly, leisure boaters don't have the luxury of filtering out Class B targets! Unless, of course, we buy rather expensive ship radars...

From earlier threads on this subject I learned that the Vesper Marine WatchMate, while not filtering Class B targets per se, can filter alarms based on various parameters, one of which is SOG. This means one could set the minimum speed as, say, 8 knots, under which few commercial ships that pose a threat rarely operate and that constitute the bulk of recreational sailing vessels that consistently activate my alarms when they tack into my CPA boundary set for the dangerous commercial ships, especially fast ferries. Sadly, OpenCPN running on a netbook that I have below on the chart table being fed by my AIS input, has very limited alarm filtering and without that function.

What was interesting in the Panbo article I cited, was the comment by Furuno Tech, viz.:

"The WA State Ferry (WSF) Fleet is the largest passenger ferry system in the western hemisphere. WSF has been a valued Furuno Customer for the past two decades and their opinions/demands carry a lot of weight with our company. The fact that Andy reaffirmed their same concerns in his explanation justifies the reasons why these settings exist on our products.
Furthermore, as Andy points out, because of feedback from the WA State Ferry Captains and other Furuno customers, we have already implemented certain types of AIS Alarm Filtering Criteria to enhance the usefullness of the AIS Target Overlay capability on many of our products, including Navnet 3D and other Furuno radar/plotter systems. Please trust that these new features have not been implemented to mask certain classes of AIS Targets but instead, we are trying to make AIS monitoring for ALL CLASSES more useful and less distracting to our customers, thus improving navigation safety and the usefulness of our products."​

This led me to examine the Furuno FAR-2107 Operator Manual and infer that to completely disable AIS Class B display and alarms entails two separate passes through a complex menu structure; not something for a deck officer to be doing when busy with entering a crowded port area. And, by the same token, just as tedious (and easily forgotten) to reset to 'ON' when leaving. An example of just the display setting below:

4.3 AIS Display Filter
If there are too many AIS targets on the screen you may wish to remove unnecessary ones. You may remove targets by distance from own ship, speed, class and length. For example, you might want to remove slow moving targets, as they normally do not require close monitoring.

1. Left-click the MENU box to open the menu.
2. Select 4 [TT]
3. Select 7 [AIS DISP FILTER].

1 BACK
2 MAX RANGE OFF/ON 0NM
3 MIN SHIP SPEED OFF/ON 0.0kn
4 EXCEPT CLASS B OFF/ON
5 MIN SHIP LENGTH OFF/ON
​

4. Set items 2-5 referring to the description below.

MAX RANGE: Any AIS target beyond the range set here will not be shown.
MIN SHIP SPEED: Any AIS target slower than this setting will not be shown.
EXCEPT CLASS B: Select ON to remove Class B AIS targets.
MIN SHIP LENGTH: Any AIS target whose length is shorter than this setting will not be shown.
​

5. Push the right button twice to close the menu.
6. Select "DISP FILT" from the AIS DISP box.
​

 

[pvb]

I don't think the Furuno menu you've quoted is much more complex than a lot of the button pushing we do on our plotters. However, you raise a good point in suggesting they might not bother to turn Class B targets back on. Another reason for not trusting Class B transponders to guarantee that you're seen!

 

[BrianH]

I don't think the Furuno menu you've quoted is much more complex than a lot of the button pushing we do on our plotters. However, you raise a good point in suggesting they might not bother to turn Class B targets back on. Another reason for not trusting Class B transponders to guarantee that you're seen!

Again, I must agree with you. I have seen enough AIS Class A static data from clearly underway ships showing them as 'Moored', for example, to not trust operator entry data.

 

[Joker]

It was obvious from the beginning that widespread take-up of Class B transponders had to lead to ships simply filtering them off their radar screens.

One visualises the following exchange in a court of law:

QC: 'My client had an AIS transmitter. Why did you not see him?'
Mariner on trial: 'We filtered people like him out ...'
QC: incredulous silence followed by: 'You mean you switched off a vital piece of safety equipment?'

 

[BrianH]

One visualises the following exchange in a court of law:

QC: 'My client had an AIS transmitter. Why did you not see him?'
Mariner on trial: 'We filtered people like him out ...'
QC: incredulous silence followed by: 'You mean you switched off a vital piece of safety equipment?'

Easily countered by an expert witness for the defence in the form of Dr Andy Norris, who has publicly defended such action with:

"Therefore, filtering of all AIS Class B targets, together with preventing their activation, may be the appropriate strategy in such areas to avoid possibly dangerous alarm distraction of the bridge team."​

The trial would have a shadowy proxy defendant - the IMO, who probably did not foresee the eventual outcome of introducing the Class B protocol and the vague IEC guidelines that do not proscribe any manufacturers' actions to bow to shipowners' dictum. It would not have been difficult to have mandated an algorithm to allow filtering but to override and force display and alarm at a certain collision danger point regardless of active/sleeping, Class A/B - which I earlier posted to be my (mistaken) impression of what was in effect.

It is notable to me how little comment is generated by this condition - that ships suppress Class B AIS targets on their radar overlays. We all knew that the original, primitive MKD displays commonly fitted in the early days of AIS were no realistic protection. But with modern upgrades there seems to be just as much requirement for defensive strategies and that the AIS receiver has infinitely more value than the transmitter, which has always been my own philosophy.

Perhaps the deafening silence has something to do with collective guilt by all those responsible for unnecessary 'look-at-me' AIS Class B signals in such places as the Solent, that have initiated the situation...

 

[JackIron]

Sorry...back to this forum after many years of watching. But just to clear up this issue of AIS filtering (unless it has already been covered). It is true that Class A vessels can place a form of filter on a target, but the watch keeper cannot remove the target from the screen. The filtering allows differentiation of targets, in order that a watch keeper can make a better assessment regarding type of vessel therefore its rate of turn. This in turn should improve the situational awareness of the watchkeeper. Many of the issues with lack of Class B visibility relate to poor installation. Never forget that the quality of data recieved on a targets bridge, is entirely dependent on the correct installation of your equipment. Having worked with AIS on both Class A and Class B vessels, many class B vessels 'disappear' at very short range, often due to use of poor quality VHF splitters. Those utilising an independent aerial have a far greater effective range. (splitters are not bad per se, but it introduces a possible error source)
Active Radar Transponders are extremely useful, but in choice the AIS is a far more effective tool. A combination of both is ideal. Standard radar reflectors offer very poor returns, you are far more likely to be lost in the clutter, than you are to be 'ignored' via AIS. Please also bear in mind that any incident involves a long error chain, and poor training in the use an interpretation of AIS data may be just one contributing factor - the presence of AIS itself is never a contributing factor. Me? I would never sail without a Class B transponder on my boat, couple this to an effective application of Rule 2, and the seas are a far safer place.


p.s Sorry forgot also to mention that in areas of high traffic, AIS reduces the cell size and removes targets at greater ranges to improve clarity.

 

[BrianH]

It is true that Class A vessels can place a form of filter on a target, but the watch keeper cannot remove the target from the screen.

The Furuno FAR-2107 Operator Manual implies otherwise (see post #44) As does the Furuno representative's comments in the Panbo article (http://www.panbo.com/archives/2010/12/class_b_ais_filtering_the_word_from_dr_norris.html#more) and quoted in that same post. That is my interpretation, I am willing (nay, eager) to be proved wrong.

 

[JackIron]

I have never seen a piece of equipment that has allowed removal of a target in its entirety. If there is indeed a piece of equipment that can do this (and reading the Furuno spec in more detail I now concur that is does imply this) it is highly concerning. The only filtering experienced is the ability to deactivate a Class B vessels data, to 'declutter' the CPA/TCPA list. However once any target breaks the alarm zone, it will alarm. I simply cannot imagine a scenario where you would want to switch off targets entirely - select and monitor those that offer the greatest possibility of a situation developing, yes - but certainly not 'switch off' a target, and differentiation between A and B targets is already simplicity itself. The danger is that if a watch keeper 'could' then at some point someone will. I'd have to get into the performance standards to ID this issue. Having sailed a fair way in the last year, anytime I have wanted clarification on a vessels intentions and requested the confirmation that my AIS was visible, the reply has always been in the affirmative. Now i am back shoreside this could form the basis of an interesting study. I am closely involved with the training and certification of watchkeepers so stand by and I'll look into this more.........

 

[Scotty_Tradewind]

After reading the postings immediatly above....

I think I'll pay even more attention to avoiding 'THEM' rather than 'THEM' avoiding 'ME'!

S.

 

[JackIron]

Ha ha - its really not that bad out there. We seem to be concentrating on one particular tool, in a plethora of skills and equipment at the disposal of the watch keeper. The academic question is how to resolve the grey areas that exist in the legislation that surrounds any new piece of equipment, and then how that is interpreted by the various manufacturers to ensure mistakes through lack of training are not made (ECDIS is a classic example of this). The regs on AIS dont provide complete clarity, the standards do call for the ability to declutter a sleeping target, but SOLAS V - Annex 17 does call for any target (sleeping or not) to activate an alarm on entering the minimum CPA/TCPA parameter - (Class A or B). The lack of clarity in discussion here is whether the target having been 'removed' might be removed from this function. i am reassured however that with this need being in SOLAS V it would be a desperately incompetent manufacturer that would allow this to occur. It does however lack complete clarity when reading the manual. The fact remains the interpretation of the manual when not read in parallel with the standards nor the SOLAS requirements could be interpreted 'for the worst'. My next task is to get onto a Class A boat with this function and test this out.....or I suppose i could just phone Furuno.....but in reality I think you have little to worry about - whether decluttered or sleeping or activated - you will alarm when you hit the target vessels CPA/TCPA minimum parameter - you cannot be 'turned off'

 

[BrianH]

in reality I think you have little to worry about - whether decluttered or sleeping or activated - you will alarm when you hit the target vessels CPA/TCPA minimum parameter - you cannot be 'turned off'

Great that you have the facilities to check this out, Jack. It is indeed a grey area and I look forward to your professional opinion on what is truly implemented on the majority of ECDIS and ARPA equipment. Thanks for that.

 

[pvb]

Ha ha - its really not that bad out there. We seem to be concentrating on one particular tool, in a plethora of skills and equipment at the disposal of the watch keeper. The academic question is how to resolve the grey areas that exist in the legislation that surrounds any new piece of equipment, and then how that is interpreted by the various manufacturers to ensure mistakes through lack of training are not made (ECDIS is a classic example of this). The regs on AIS dont provide complete clarity, the standards do call for the ability to declutter a sleeping target, but SOLAS V - Annex 17 does call for any target (sleeping or not) to activate an alarm on entering the minimum CPA/TCPA parameter - (Class A or B). The lack of clarity in discussion here is whether the target having been 'removed' might be removed from this function. i am reassured however that with this need being in SOLAS V it would be a desperately incompetent manufacturer that would allow this to occur. It does however lack complete clarity when reading the manual. The fact remains the interpretation of the manual when not read in parallel with the standards nor the SOLAS requirements could be interpreted 'for the worst'. My next task is to get onto a Class A boat with this function and test this out.....or I suppose i could just phone Furuno.....but in reality I think you have little to worry about - whether decluttered or sleeping or activated - you will alarm when you hit the target vessels CPA/TCPA minimum parameter - you cannot be 'turned off'

I'm afraid you're wrong there too. Modern ship radars have to comply with IMO regulation MSC.192(79), which provides for the facility to filter Class B targets out. There aren't many operator manuals for ship radars on the internet, but there is the Furuno manual for their FAR2807 series ship's radar, you can read it here - http://www.furunousa.com/ProductDocuments/FAR21x7%2028x7%20Operator's%20Manual%20P%20%204-8-11.pdf

In section 4.12.3 it tells you how to turn off the CPA/TCPA collision alarm for Class B vessels.

 

[JackIron]

Wow - I hadnt spotted that - its amazing if this is possible. I have run this past a few master mariners here who could not even conceive this was possible nor desirable. A target of whatever size/class is a target - Class A, B, and no 'class at all'.....hence the assumption that the SOLAS wording would encompass you as an existing target - displayed, filtered, sleeping, or otherwise. by the time you are in traffic of such density that requires you to do this, or indeed reduce your CPA/TCPA alarm parameters to exclude such 'targets' you are well beyond the functionality of AIS as a collision avoidance tool and down to constant close monitoring of radar and mark 1 eyeball, probably with a helmsman and extra look outs on hand. So why on earth have such functionality?

Your comment on filtering is well known - but it is just that - a filter - not a 'remove from the system entirely' function. The ships AIS has received your data - the filter is on the display setting in order for the mariner to set display function appropriate to the situation - that data is still there - and it is that that should activate the alarm.

If you look at the wording of SOLAS its states "Dangerous target - If an AIS target (activated or not) is calculated to pass pre-set CPA and TCPA limits, it will be classified and displayed as a dangerous target and an alarm will be given." Does the 'or not' extend to mean both sleeping and filtered? You could certainly argue so.

In all sensible opinion whether a target has been filtered from the display (it should still 'exist' - you are transmitting your position and are in essence a 'target') and hence should activate the alarm. If indeed this is the case i would suggest that SOLAS requires amending....ensuring with complete clarity that to set a piece of equipment in this way would be in contravention of SOLAS V Annex 17 - a very serious matter indeed, and clarity withing the wording of SOLAS is needed.

You should also note the following header to annex 17 - AIS is a new and untried system, but with the potential to make a significant contribution to safety. It is particularly important therefore that during the early years of implementation its potential is fully assessed by mariners, taking full account of the MCA Guidance and the IMO Guidelines. The MCA will welcome feedback on the use of AIS from ships or companies.

Whilst we are far from a 'new' piece of equipment clearly the regs/standards have yet to mature. I believe some further investigation is needed, no?

 

[pvb]

Wow - I hadnt spotted that - its amazing if this is possible. I have run this past a few master mariners here who could not even conceive this was possible nor desirable. A target of whatever size/class is a target - Class A, B, and no 'class at all'.....hence the assumption that the SOLAS wording would encompass you as an existing target - displayed, filtered, sleeping, or otherwise. by the time you are in traffic of such density that requires you to do this, or indeed reduce your CPA/TCPA alarm parameters to exclude such 'targets' you are well beyond the functionality of AIS as a collision avoidance tool and down to constant close monitoring of radar and mark 1 eyeball, probably with a helmsman and extra look outs on hand. So why on earth have such functionality?

It's rapidly becoming a simple necessity in some crowded waters, caused by the proliferation of Class B transponders. If you couldn't cancel automatic Class B alarms, the watchkeeper would go mad with the noise of the constant alarms, not to mention the screen clutter making it impossible to interpret the situation clearly.

 

[Mariner69]

Sorry, at JackIron, you should be aware that AIS was not originally designed for collision avoidance but was purely to provide a recognised maritime plot for security purposes. It would make more sense to use a IFF (Identify Friend or Foe) system wholly linked to the radar.

In 1982, when doing Extras in Cockcroft's class at City of London Poly (Sir John Cass) this was being mooted along with the first ARPA's. The ship owners did not see a reason for it and could not afford it. Like yachties, the wind is free so why should we pay money for anything? IMO has a very, very strong vested interests section.

I have been a delegate at IMO and can tell you that treacle flows quicker in many cases. Dangerous Goods legislation was taking ages (about 5 years) to be agreed but come 911 the USA saying "you have two choices Friend or Foe" had the ISPS code passed in about 18 months.

The advantage of IFF is that it links the identify to the radar target. AIS doesn't and can be played with if someone is so inclined. It is also easily jammed hence the eLORAN moves.

More worrying is that in ECDIS layers can be omitted and checking a passage can be harder than running an eye down the course lines drawn on the paper charts.

We invent new technology and a whole new raft of problems follow on. Training is the answer, whatever the question.

 

[bobgarrett]

I am glad I got involved in this discussion as it has clarified some things for me, especially whether there are AIS displays which can have Class B vessels filtered from their screens. As pvb has shown some do exist.
It is interesting though that my previous searches had not found them; but I had been looking at current products. Looking at current Furuno products this feature appears to have been excluded now - unless I am missing it. I have looked at the FMD3200/3300 and FA-170 units.
Could it be that manufacturers now think this might not be such a good feature? Of course there will still be some older units out there.
As stated by others IMO do not present AIS as a Collision Avoidance tool but do say it might be one day.

 

[GHA]

I am glad I got involved in this discussion as it has clarified some things for me, especially whether there are AIS displays which can have Class B vessels filtered from their screens. As pvb has shown some do exist.
It is interesting though that my previous searches had not found them; but I had been looking at current products. Looking at current Furuno products this feature appears to have been excluded now - unless I am missing it. I have looked at the FMD3200/3300 and FA-170 units.
Could it be that manufacturers now think this might not be such a good feature? Of course there will still be some older units out there.
As stated by others IMO do not present AIS as a Collision Avoidance tool but do say it might be one day.

Do a search on panbo and gcaptain - it does seem that one foruna model if you jump through enough menu hoops you can switch off class b targets on the display but they will get turned on again if in the acquisition zone unless you dig intop the menu deeper and turn off cpa alarms as well, or something like that. Some interesting comments on gcaptain from the big boys, no one knew that deep in the menus how to do it and wouldn't bother anyway. And everything will still show up on the the ais transponder.
All in all nothing but an enduring web red herring in the real world.