Class B AIS

[richardbrennan]

Got caught out in the thick fog that rolled into the Solent yesterday afternoon whilst sailing back from Cowes to Portsmouth. I called Southampton VTS to check whether a tanker I had on AIS was intending to use the North Channel and, as part of the conversation, was told that they filtered out Class B transmissions, which is perhaps not surprising when you think about it. Did not see a thing from about 2 miles west of Gilkicker until No 4 Bar Buoy approaching Portsmouth, but QHM Portsmouth also confirmed they did not have our AIS signal but did have us on radar; he was too busy for me to ask if again this was filtered out but I suspect it was. One of the IOW ferries called up QHM asking about targets in the Outer Swashway, one of which was me, but again he did not appear to be receiving our AIS signal. I checked the set when back in the marina and we were definitely transmitting. I can understand them filtering out the hundreds of returns they would get on a fine weekend, but I was a bit surprised the ferry at least did not have our transmission given the visibility was about 20 metres at best; I suppose one has to be grateful that at least we new where they were!

 

[pvb]

Lots of boat owners have installed Class B equipment in the false belief that shipping will see them.

 

[Cardo]

Lots of boat owners have installed Class B equipment in the false belief that shipping will see them.

Certainly works when crossing the channel. All the big boats avoided us.

 

[awol]

Certainly works when crossing the channel. All the big boats avoided us.

How many hit you before AIS?

 

[Cardo]

How many hit you before AIS?

To be fair, it could be as a result of radar contact, but I've certainly noticed that all the big boats, as soon as they appear on our AIS and are due to go anywhere near us they will adjust course ever so slightly to miss us by a safe margin.

 

[awol]

To be fair, it could be as a result of radar contact, but I've certainly noticed that all the big boats, as soon as they appear on our AIS and are due to go anywhere near us they will adjust course ever so slightly to miss us by a safe margin.

My experience was that they (or 99.99...%) always did. The big advantage of AIS is that the ship course changes are visible and stop the WAFIs from milling around like headless chickens.

 

[Joker]

This has me intrigued.
Scenario:
Big boat filters out Class B AIS.
Big boat runs down small boat broadcasting Class B.
Come the court case, barrister asks: 'Why did you not see my client? He was broadcasting an AIS signal?'
Answer: 'We were filtering those signals out.'
Immediate cue for suing the skipper for umpteen millions on the grounds of negligence.

 

[Twister_Ken]

Do the IoW ferries have AIS receivers?

 

[onesea]

Do the IoW ferries have AIS receivers?

Yes

"The regulation requires AIS to be fitted aboard all ships of 300 gross tonnage and upwards engaged on international voyages, cargo ships of 500 gross tonnage and upwards not engaged on international voyages and all passenger ships irrespective of size."
http://www.imo.org/OurWork/Safety/Navigation/Pages/AIS.aspx

 

[Robin]

Lots of boat owners have installed Class B equipment in the false belief that shipping will see them.

I put that argument forward many times yet when we upgraded the electronics on our new to us boat we have still installed an AIS CLASs B transponder, it has a switch that we can use to stop OUR data from being transmitted when we wish not to be seen ( known as silent, or 'piracy' mode) but we also have HD radar so we can see others doing the same who might not be showing on our AIS receiver/display, that way we can also 'see' the fishing boats etc not required to have AIS as well as inconvenient lumps of land that could otherwise cause us problems

Over here there are folks who look at AIS websites on line on their Ipads/Iphones etc convinced that is just as effective as having a marine AIS or radar

 

[Sandy]

Lots of boat owners have installed Class B equipment in the false belief that shipping will see them.

I am of the opinion that it is there for us to see them not them us.

 

[Colvic Watson]

I am of the opinion that it is there for us to see them not them us.

Yes. I suspect any ship will filter out class B in busy areas, I wish I could do the same but now we've joined the transponder brigade its comforting to know that the Latvian container ship bearing down on us has a little text display at the back of our bridge listing in alpha numerical format our lat and long, that'll help.

 

[richardbrennan]

Thanks for the comments. I am not surprised that both Southampton VTS and Portsmouth QHM filter out the Class B signals as they are primarily "Traffic Services" for the big boys. I can also understand the IOW ferry filtering out such signals on a clear sunny day when the Solent is wall to wall with yachts. However, I do find it surprising and not a little worrying that they were filtering them out in the conditions that were prevailing on Thursday afternoon, but comforting to a degree that at least we were showing on radar. This is more than can be said for a 40' mobo that overtook us about 25 metres away which did not show on my radar at all; that I did find alarming!

 

[pvb]

I am of the opinion that it is there for us to see them not them us.

In that case, a simple AIS receiver will suffice - no need for a transponder.

 

[Robin]

I am of the opinion that it is there for us to see them not them us.

That would be correct for the receive only AIS models, like a Garmin AIS300 for example but the OP was referring to the AIS receive and transmit versions which is what we have installed on our boat, in the form of a Garmin AIS600. IN our case we have the 'ability to 'see' others with radar, without AIS so it is less concerning to us that there are vessels filtering out class B transmissions. However the point here is that there are some who think their AIS transmissions will be seen by all big ships. FACT is that only newer vessels required to have AIS may have the AIS contact displayed on a plotter or a radar screen as opposed to just appearing in a list of nearby vessels that a watch officer may or may not bother to refer to regularly. IT is my feeling that some people are unclear about what is possible and what may actually happen in practice.

 

[GHA]

may[/B] have the AIS contact displayed on a plotter or a radar screen as opposed to just appearing in a list of nearby vessels that a watch officer may or may not bother to refer to regularly. IT is my feeling that some people are unclear about what is possible and what may actually happen in practice.

Not "may" , since 2007 (.??) all new radar installations will display ais targets if on a solas ship.
http://www.panbo.com/archives/2009/04/ais_solas-style_class_b_is_not_ignorable.html
Under iec 62388
10.5.3 Filtering of AIS sleeping targets requirement: To reduce display clutter, a means to filter the presentation of sleeping AIS targets shall be provided, together with an indication of the filter status (for example by target range, CPA/TCPA or AIS target class A/B, etc.). It shall not be possible to remove individual AIS targets from the display. The filter criteria in use shall be readily available. - See more at: http://www.panbo.com/archives/2009/..._b_is_not_ignorable.html#sthash.eGzF1KLJ.dpuf

 

[Robin]

Not "may" , since 2007 (.??) all new radar installations will display ais targets if on a solas ship.
http://www.panbo.com/archives/2009/04/ais_solas-style_class_b_is_not_ignorable.html
Under iec 62388
10.5.3 Filtering of AIS sleeping targets requirement: To reduce display clutter, a means to filter the presentation of sleeping AIS targets shall be provided, together with an indication of the filter status (for example by target range, CPA/TCPA or AIS target class A/B, etc.). It shall not be possible to remove individual AIS targets from the display. The filter criteria in use shall be readily available. - See more at: http://www.panbo.com/archives/2009/..._b_is_not_ignorable.html#sthash.eGzF1KLJ.dpuf

Good to see that essels since 2007 display AIS contacts on their radars, our little saily boat one does that and it is a very useful feature.

 

[JumbleDuck]

Not "may" , since 2007 (.??) all new radar installations will display ais targets if on a solas ship.
http://www.panbo.com/archives/2009/04/ais_solas-style_class_b_is_not_ignorable.html
Under iec 62388
10.5.3 Filtering of AIS sleeping targets requirement: To reduce display clutter, a means to filter the presentation of sleeping AIS targets shall be provided, together with an indication of the filter status (for example by target range, CPA/TCPA or AIS target class A/B, etc.). It shall not be possible to remove individual AIS targets from the display. The filter criteria in use shall be readily available. - See more at: http://www.panbo.com/archives/2009/..._b_is_not_ignorable.html#sthash.eGzF1KLJ.dpuf

Didn't that just imply that they can filter out Class B, but that their screen has to tell them they're doing so? Or have I missed something?

 

[pvb]

Good to see that essels since 2007 display AIS contacts on their radars, our little saily boat one does that and it is a very useful feature.

Only those with brand-new radar systems do - the others don't have to. And even if they have the capability, Class B targets can be filtered out.

 

[pvb]

Didn't that just imply that they can filter out Class B, but that their screen has to tell them they're doing so? Or have I missed something?

You're right. Even with new radar systems, in many circumstances Class B transponders won't be seen by ships. Boat owners would get far better value by installing active radar reflectors.