AIS ..........MB&Y Feb 2012

[DAKA]

I havent got AIS yet but feel its something I need to think about however after reading this months MB&Y where it is claimed so many pleasure boats have them you cant see dangers and according to scuttlebutts, commercial shipping sees class B transponders as 'sea clutter' and removes them from the screen anyway

Does anyone have a receiver and do you find it is invaluable or a nuisance ?

 

[boatmike]

I havent got AIS yet but feel its something I need to think about however after reading this months MB&Y where it is claimed so many pleasure boats have them you cant see dangers and according to scuttlebutts, commercial shipping sees class B transponders as 'sea clutter' and removes them from the screen anyway

Does anyone have a receiver and do you find it is invaluable or a nuisance ?

I have a receiver linked to my plotter and it's invaluable. There is an open question about yachts transmitting on AIS "B" and I won't go there but certainly recieving A class is very useful if you tune your set intelligently for range and alarms. I think it's all about attitude. I always travel under the assumption that regardless of right of way anything bigger than me is a potential danger. Regardless of him seeing me, if I can see him I can avoid being run down. If this is your philosophy too then I would say that an AIS reciever is a very useful additional source of info for a modest outlay. Don't miss also that you can "see" vessels you can't on radar, like on the other side of a headland where VHF transmissions work but line of sight radar doesn't

 

[DAKA]

. Don't miss also that you can "see" vessels you can't on radar, like on the other side of a headland where VHF transmissions work but line of sight radar doesn't

I didnt know that , I need to research a lot more, thanks

 

[volvopaul]

On subject of recent mby that popped through my letterbox today.

The quality of the print and paper used in the mag at page 109 to 113 re the feature on sea lines f 43 is piss poor, surely a refund or new mag should be asked for, anyone else got such a poorly printed copy?

 

[davo99]

On subject of recent mby that popped through my letterbox today.

The quality of the print and paper used in the mag at page 109 to 113 re the feature on sea lines f 43 is piss poor, surely a refund or new mag should be asked for, anyone else got such a poorly printed copy?

No prob with mine, no diff to rest of mag

 

[SailorBill]

. Don't miss also that you can "see" vessels you can't on radar, like on the other side of a headland where VHF transmissions work but line of sight radar doesn't

I didnt know that , I need to research a lot more, thanks

I didn't know that either but now it's been pointed out it makes sense. I'm surprised AIS receiver manufacturers don't make more of this as it's potentially a very useful feature over radar.

 

[oceanfroggie]

. . . and according to scuttlebutts, commercial shipping sees class B transponders as 'sea clutter' and removes them from the screen anyway

I think the benefit is that leisure boats can see where shipping is and keep out of the way. A ship won't sink if it hits a grp tub, but it might if it hit another ship.

ie toys avoid getting run over by big stuff

 

[DAKA]

I think the benefit is that leisure boats can see where shipping is and keep out of the way. A ship won't sink if it hits a grp tub, but it might if it hit another ship.

ie toys avoid getting run over by big stuff

Im still researching this and dont really know but I deduce you are correct in that a receiver works well for avoiding shipping however there are so many class B transponders they cover over the ships so you cant see them.
It would appear you have to set the receiver to delete the class b boats.

Raggies have sort of shot themselves in the foot, in the mad rush to be seen on AIS they have over done it and have been made invisible.

Shipping apparently doesnt bother with radar as the AIS is more detailed.


It would appear a class B transponder is now near useless.

You are correct that the receiver remains a valuable tool for spotting shipping as long as you hide the class b targets.

 

[Elessar]

I havent got AIS yet but feel its something I need to think about however after reading this months MB&Y where it is claimed so many pleasure boats have them you cant see dangers and according to scuttlebutts, commercial shipping sees class B transponders as 'sea clutter' and removes them from the screen anyway

Does anyone have a receiver and do you find it is invaluable or a nuisance ?

I have the nasa one which was only just over £100.

It's fairly useless in confined waters and the alarm has to be left off. I leave the icons on screen though.

For crossing shipping lanes or in busy shipping areas it's the best £100 ever spent.

I have been contacted (by name) by ships stating their intentions, or asking mine. And I have spoken to ships, again by name, and pointed out that I am stand on and intend to do so and suggested that perhaps a CPA of 6 ft is a little small. The response is inevitably cheery and they alter course glad of the removal of any ambiguity.

Yes i know the use of VHF for collision avoidance is discouraged, but in practice since it seems to be more rather than less prevalent with ships contacting each other seemingly routinely to request clarity, to pass green to green or whatever.

[edit] the asking mine incidents were when I was in a boat with a transponder - the nasa £100 is receiver only so that couldn't have happened. voyages blurring into 1 silly me

 

[Elessar]

Im still researching this and dont really know but I deduce you are correct in that a receiver works well for avoiding shipping however there are so many class B transponders they cover over the ships so you cant see them.
It would appear you have to set the receiver to delete the class b boats.

Raggies have sort of shot themselves in the foot, in the mad rush to be seen on AIS they have over done it and have been made invisible.

Shipping apparently doesnt bother with radar as the AIS is more detailed.


It would appear a class B transponder is now near useless.

You are correct that the receiver remains a valuable tool for spotting shipping as long as you hide the class b targets.

When you are out of confined waters, especially if it is rough and dark, an AIS return from a yacht confirming that splodge in the radar clutter is in fact a yacht and it's going that way is really re assuring.

 

[Elessar]

Im still researching this and dont really know but I deduce you are correct in that a receiver works well for avoiding shipping however there are so many class B transponders they cover over the ships so you cant see them.
It would appear you have to set the receiver to delete the class b boats.

Raggies have sort of shot themselves in the foot, in the mad rush to be seen on AIS they have over done it and have been made invisible.

Shipping apparently doesnt bother with radar as the AIS is more detailed.


It would appear a class B transponder is now near useless.

You are correct that the receiver remains a valuable tool for spotting shipping as long as you hide the class b targets.

The heading information is useful too. When a ship sees you they often make a small course correction of just a few degrees. Not what the colregs say I know but it's what happens. Knowing about that nudge of their course is a useful bit of info, that would be hard to spot and would definitely take longer to spot by other means.

In busy shipping areas I write down the last 3 digits of the MMSI as a reference ID, the heading, speed and bearing to the other vessel, all that data from the AIS screen.
Noting that info every 10 mins gives excellent collision avoidance info and the HB compass stays in the drawer.

I know MARPA is supposed to do all of the above, but when it's rough MARPA info isn't steady and it's prone to losing lock. As with everything navigational I use both though.

 

[Elessar]

I didnt know that , I need to research a lot more, thanks

AIS is just digital VHF comms. If you could speak on a VHF you can probably "see" them on AIS.

 

[RobbieW]

Shipping apparently doesnt bother with radar as the AIS is more detailed.

Not the impression I was left with following a RIN talk at Warsash College in April 2011. The talk was about the evolution of Integrated Navigation Systems and covered, in part, both RADAR and AIS. Your statement may have some basis on board a well funded, modern (or modernised) ship where the two would be on one display anyway. Many of the worlds merchant shipping fleet are niether, staying with only what is required to operate legally.

The impression I left the room with was that RADAR should still be considered the primary poor conditions collision avoidance tool used by shipping.

That said, AIS is a damn sight easier to use on a small boat than RADAR but not all targets are required to have AIS.

 

[boatmike]

Having read recent posts I am concerned that whenever this subject arises it becomes a radar v AIS discussion. I think we should start by saying that neither are perfect and both should be used with discretion. When I got my original training I was told that there were cases of "radar assisted collision" The same could happen with AIS if the information recieved is relied too heavily upon. Both are "aids to navigation" not navigation instruments. If you work on the basis that all information is adding to the grand picture and should be seen in context then it becomes clear that AIS and radar compliment one another. The assumption that commercial vessels do or do not see you on either is dangerous. Personally I don't care a lot, my assumption will always be "he can't see me" . I also make the assumption that even if there is now't on either screen it doesn't mean there is nothing there. Call me paranoid perhaps but I will continue to assume that they are all out to sink me if they can and it's my job to make sure they cant!

 

[Elessar]

Call me paranoid

Nope.

Just wise.

 

[Spi D]

AIS online

For those who wan't to see what is't all about here's an online service to play with:
http://www.marinetraffic.com/ais/default.aspx?centerx=30&centery=25&zoom=2&level1=140

Ofcourse only useful when you have internet access, but these days sitting in front of the 'puter it is interesting

 

[timbartlett]

If you were riding a bicycle along a busy road at night, would you turn your lights off in case they bothered the HGV's?

I know I wouldn't! But it seems to me that the arguments against Class B are exactly the same as arguing that bicycles shouldn't have lights!

And those who say "ah but it's different in the Solent": I can see your point, and I agree that in very crowded waters there is a case for switching AIS B off (just as there's a case for switching nav lights and fog signals off in clear daylight). But how do you switch your radar cross section to zero? Because unless you operate a "stealth" boat, your radar contact will be contributing to the "clutter" anyway!

And as for the "filtering" meme: Intelligent filtering -- removing clutter without removing potential collision threats is, IMHO, a good idea, and one which will eventually filter down to more small craft. But if a ship's OOW somehow manages to find a combination of control settings that deliberately filters out all Class B targets, and is then involved in a collision, it is extremely unlikely that he will keep his certificate, and distinctly probable that he will find himself in jail while his ship's owners fork out a fine. Deliberately flouting Rule 5 is a career-damaging move.

 

[benjenbav]

DAKA - you know you want to. They don't call 'em "targets" for nothing y'know.

 

[Hurricane]

If you were riding a bicycle along a busy road at night, would you turn your lights off in case they bothered the HGV's?

I know I wouldn't! But it seems to me that the arguments against Class B are exactly the same as arguing that bicycles shouldn't have lights!

And those who say "ah but it's different in the Solent": I can see your point, and I agree that in very crowded waters there is a case for switching AIS B off (just as there's a case for switching nav lights and fog signals off in clear daylight). But how do you switch your radar cross section to zero? Because unless you operate a "stealth" boat, your radar contact will be contributing to the "clutter" anyway!

And as for the "filtering" meme: Intelligent filtering -- removing clutter without removing potential collision threats is, IMHO, a good idea, and one which will eventually filter down to more small craft. But if a ship's OOW somehow manages to find a combination of control settings that deliberately filters out all Class B targets, and is then involved in a collision, it is extremely unlikely that he will keep his certificate, and distinctly probable that he will find himself in jail while his ship's owners fork out a fine. Deliberately flouting Rule 5 is a career-damaging move.

We've been transmitting Class B since it was first launched/released.
And, by default its always on when we are out.
But earlier this year we found another problem with the system.
One you wouldnt think of.
We cruise in the Western Med.
Spain is OK but as soon as you hit French waters, the coast guard is forever calling you.
They see the Class B AIS on their screens and call you every half hour os so.
Its a real PIA!
So much so that we simply switch the transmission off.

Other than that, I agree with you - its best to be seen as much as possible.

Two other comments
Nobody seems to have pointed out that AIS is inheritantly inaccaruate.
By inaccurate, I mean that you cant rely on its position.
With Radar, you receive an echo from a definate object.
With AIS you are relying that the transmitting vessel is acutally transmitting the correct information - and that the data is recent enough.

Also
In my experience, class B to class B (ship to ship) is very poor.
We often see the other vessel using our eyes before it appears on the AIS.
Remember that Class B gets a very poor second place transmission schedule to Class A transmissions .

My three pennyworth

 

[boatmike]

No one suggested you should turn your lights off Tim. The question is "how useful is transmitting on AIS B" which is after all a recent innovation relatively speaking. My argument generally is that it is much more expensive than "recieve only" and while it possibly might be useful in some circumstances it's certainly not essential and might be of no use at all. The argument that if every little boat has it and transmits all the time we will get information overload is inescapable. If this happens ships will certainly filter out B. If you really want to be seen then I think an active radar transponder should be considered to be at least as useful but hey if you can afford everything then have them both, but don't rely even then on the other guy seeing you. Proceed with maximum caution and assume he can't. Having a receiver however, assuming you already have a chartplotter, is relatively cheap and enables you to see them.