so an old question - SeeMe or AIS?

[Bosun Higgs]

Spent too much elsewhere to install both this year so the question is which one?

At the moment I have a rain catcher type radar reflector that is used only when I hoist it up the forestay. Obviously no AIS. But AIS would not spot the fishing boats etc without transmitters and is a passive system ie it warns me of them but not them of me. Unless I get the transmitter as well but then thats even more pricey and whose to say big ships wont turn off the yottie signals on account of their being too many?

A SeeMe on the other hand warns them of me, but as I understand it would not be triggered by the latest digi radar systems. And these new systems will become more common so that problem will get worse.

I suppose I could sail as I have done for decades ie without spending anything more. But you have to keep up with the times dont you?

So which?

 

[Ex-SolentBoy]

Both.
They do different jobs.
Or none.
Or either.

It's certainly not a case of which one, unless you want to decide which job is more important to you.

 

[Sans Bateau]

AIS puts the responsibility for your safety with you, your watch, where it should be. SeaMe relies on (you hope) someone is looking at their radar. You say AIS will not help with fishing boats without transmitters, but whos to say a fishing boat will be looking at their radar and be concerned about you when on a trawl run, no, he'll still expect you to get out the way (as the IRPCS require). For me AIS is indispensable, but dont crowd the screens of others AIS receivers with your AIS transponder, a receiver alone is all you need.

 

[Scotty_Tradewind]

I went for AIS first.

My theory being that it is firstly my responsibility to miss everybody else although the Echomax does alarm you when in receipt of a radar beam.
I did have a stand-alone by NASA.
I then bought a NASA AIS 'engine' and put that through my plotter - much improved.
I then added an 'x' band SeaMe

Changing boats ( I still have to use these at sea ) and recently fitted.....

A Digital Yacht AIS aerial/engine through my plotter and an Echomax dual band radar reflector to try and influence all craft with radar with my prescence.
I chose the Echomax this time as the reviews favoured it. The jury is still out on them both.

 

[dt4134]

A SeeMe on the other hand warns them of me, but as I understand it would not be triggered by the latest digi radar systems. And these new systems will become more common so that problem will get worse.

Do you have any information on the problem with digi radar systems? Presumably this is some sort of chirp type radar. I guess the SeeMe would be triggered but if the radar set is only looking for an encoded return then it may reject the pulse from the SeeMe. Is it anything more than an urban (marina) myth that merchant vessels are using it?

 

[Twister_Ken]

I went for AIS first.

A Digital Yacht AIS aerial/engine through my plotter and an Echomax dual band radar reflector to try and influence all craft with radar with my prescence.
I chose the Echomax this time as the reviews favoured it. The jury is still out on them both.

I have the same set-up exactly. Seems to work quite well. I haven't been run down yet.

Mind, I wasn't run down in 30 something years of sailing without either of them.

 

[timbartlett]

At the moment I have a rain catcher type radar reflector that is used only when I hoist it up the forestay.

Waste of space but keeps you legal -- if anyone bothers to check.

Obviously no AIS. But AIS would not spot the fishing boats etc without transmitters and is a passive system ie it warns me of them but not them of me. Unless I get the transmitter as well but then thats even more pricey and whose to say big ships wont turn off the yottie signals on account of their being too many?

AIS can be active or passive. Not having AIS transmit (A or B) is like riding a bicycle without lights -- you may be able to see others, but isn't it better if they can see you as well? Ships cannot selectively "turn off" AIS B (at least, not easily). And doing it deliberately (IF there is some obscure setting that allows it to be done) would be a seriously career-damaging move. "Filtering" is a completely different issue: it suppresses non-hazardous targets, making the dangerous ones more conspicuous. The development of filtering (and the fact that it is now compulsory on new installs on solas vessels is a sign of how much AIS is improving with time.)

A SeeMe on the other hand warns them of me, but as I understand it would not be triggered by the latest digi radar systems. And these new systems will become more common so that problem will get worse.

RTE's are great. Digital radars are no problem. I think what you are thinking of are "Broadband" radars -- which account for only a small proportion of small craft radars, and none at all on ships. But bear in mind that single-frequency RTEs will only work on X-Band radars. Most ships use X-band and S-band -- and are particularly likely to use S-band in rough weather or heavy rain.

 

[Twister_Ken]

But bear in mind that single-frequency RTEs will only work on X-Band radars. Most ships use X-band and S-band -- and are particularly likely to use S-band in rough weather or heavy rain.

Agreed. But it would be Luddite to buy a single-frequency RTE nowadays. X and S band versions have been available for a couple of years or more.

 

[LadyInBed]

This has been asked here, here and here

PS - It might be an old question but the answer stays the same

 

[Bosun Higgs]

This has been asked here, here and here

PS - It might be an old question but the answer stays the same

Ah, but does it? Or do things move on?

 

[Bosun Higgs]

Do you have any information on the problem with digi radar systems? Presumably this is some sort of chirp type radar. I guess the SeeMe would be triggered but if the radar set is only looking for an encoded return then it may reject the pulse from the SeeMe. Is it anything more than an urban (marina) myth that merchant vessels are using it?

No I dont have any information but it seems to me that a reflector designed to respond on the same frequency to a strong signal burst is unlikely to work with a very weak continuous signal of varying frequency. And I'm not aware of any reason why big ships would not be just as likely to chose a new type radar as the old type.

It would be great if someone with real knowledge could settle the question for us.

P.S. According to MES, The Echomax and SeeMe do work with the latest digi radars so I wuz rong - again!

 

[timbartlett]

No I dont have any information but it seems to me that a reflector designed to respond on the same frequency to a strong signal burst is unlikely to work with a very weak continuous signal of varying frequency. And I'm not aware of any reason why big ships would not be just as likely to chose a new type radar as the old type.

It would be great if someone with real knowledge could settle the question for us.

P.S. According to MES, The Echomax and SeeMe do work with the latest digi radars so I wuz rong - again!

...Digital radars are no problem. I think what you are thinking of are "Broadband" radars -- which account for only a small proportion of small craft radars, and none at all on ships.

You are confusing two totally different "new" types of radar.
"Digital" refers to the way the radar pulse is processed after it gets back to the radar that transmitted it. Digital radars are perfectly capable of triggering and displaying RTEs, and are fitted to ships and many small craft.

"Broadband" (FMCW) radars transmit a totally different kind of "pulse"(not really a pulse at all) and at a few milliwatts instead of a few kilowatts. Even if they were capable of triggering an RTE, they are not capable of displaying it. Ships don't have FMCW radar because there are no FMCW radars that meet the IMO requirements, and they are (as yet) fitted to only a small proportion of small craft.

But of course, I know nothing about these things.

 

[fireball]

Not having AIS transmit (A or B) is like riding a bicycle without lights -- you may be able to see others, but isn't it better if they can see you as well?

Disagree with that - riding a bike without lights during the day isn't even an issue - vehicles can see you with little problem - (if they look!)
At night lights on bikes are helpful - along with reflective clothing - if you're going to be riding with traffic - but if you're riding alone on deserted cycle paths then the only purpose they serve is to show you were you're going and use batteries ...

RTE's are great. Digital radars are no problem. I think what you are thinking of are "Broadband" radars -- which account for only a small proportion of small craft radars, and none at all on ships. But bear in mind that single-frequency RTEs will only work on X-Band radars. Most ships use X-band and S-band -- and are particularly likely to use S-band in rough weather or heavy rain.

We're discussing here whether ships or not can see us (class B) on AIS. We've already cast doubt over the completeness of our own AIS reception - as small ships/fishing vessels and other leisure vessels will not always appear...

Therefore I would ask - which is more beneficial - ensuring you appear on a slowly emerging technology or ensuring you appear on (what I take to be) their primary long range collision avoidance tool - ie Radar ... ??

The answer is highly dependant on the individual vessel, skipper, intended cruising grounds and their aversion to risk....
For me, in the Solent area which is my primary sailing area - AIS B is generally superfluous - even AIS A is tenuous. In areas where leisure craft are less dense then Class B will start being of use and Class A reception is very useful.

Once leisure devices start enabling the filtering out of Class B display and/or alarms I would be happier - I believe you've said that the commercial devices can filter out non-hazardous targets - but how is non-hazardous defined? Sailboats don't drive on rails and their course will flip in and out of an alarm area with surprising frequency - these occasional alarms are bad enough with Class A on a x channel jaunt without adding to them!

 

[JSYmartini]

a receiver alone is all you need.

Wouldn't be much use if everyone took this view...

 

[GeorgeLlewellin]

Transponder alarm.

Echomax does alarm you when in receipt of a radar beam.

So does the SeaMe, but you have to wire it up with your own alarm. George

 

[Spuddy]

I suppose bridge practice comes into this. I was chatting to someone recently who was picked up in Atlantic by a VLCC. There was AIS on the bridge but tucked away more or less out of sight; they relied on radar. It seems that the officers had found other ships and fishing boats had AIS switched off - dunno why if it is difficult to turn off and jeopardises career but there it is.
I found it a useful observation about what actually goes on. Since my boat is small and low on power reserves I might look into one of those French hand-sized radar alarms. Lost my link - anyone know the name?

 

[timbartlett]

We're discussing here whether ships or not can see us (class B) on AIS. We've already cast doubt over the completeness of our own AIS reception - as small ships/fishing vessels and other leisure vessels will not always appear...

If you haven't got it, there is no doubt at all ... you won't!

Therefore I would ask - which is more beneficial - ensuring you appear on a slowly emerging technology or ensuring you appear on (what I take to be) their primary long range collision avoidance tool - ie Radar ... ??

There's no way you can ensure you appear on either of them.

Once leisure devices start enabling the filtering out of Class B display and/or alarms I would be happier - I believe you've said that the commercial devices can filter out non-hazardous targets - but how is non-hazardous defined? Sailboats don't drive on rails and their course will flip in and out of an alarm area with surprising frequency - these occasional alarms are bad enough with Class A on a x channel jaunt without adding to them!

Some leisure devices already do have excellent filtering. Agree with you about frequent changes of course. That's why it's better to use track.

I suppose bridge practice comes into this.... dunno why if it is difficult to turn off and jeopardises career but there it is.

The IMO carriage requirements for equipment change frequently, but often have very long phase-in times -- often decades. So there are still ships running around with the three-line minimal keyboard AIS units that were introduced more than ten years ago. They were next to useless, and did a huge amount of harm to the credibility of AIS -- harm that manifests itself in threads like this.

For a junior officer on such a ship to make a genuine mistake by forgetting an obscure and hard-to-use piece of equipment tucked away at the back of the bridge might not be a career-wrecking move. But for his counterpart on a modern ship, with AIS targets display on his primary navigation radar -- to deliberately seek out an obscure control sequence in order to over-ride the process that gives AIS targets the same status as ARPA targets would be a very different matter. Its the difference between shoplifting and walking out of a shop having forgotten to pay for the packet of chewing gum amongst the 100 items in your trolley

Since my boat is small and low on power reserves I might look into one of those French hand-sized radar alarms. Lost my link - anyone know the name?

Do you mean this:http://www.ciel-et-marine.com/pages/indexpag.html?

 

[fireball]

There's no way you can ensure you appear on either of them.

Ok - point taken ... ...

Some leisure devices already do have excellent filtering. Agree with you about frequent changes of course. That's why it's better to use track.

Which ones? And do I guess that some devices can use something like an average track to predict where the vessel is going to be rather than the instantaneous SOG/COG ? Effectively dampening/smoothing the course .. ?

 

[Scotty_Tradewind]

This second time of going for an active radar reflector I chose the dual band version.
Quite a bit more costly but when I discussed all the add-ons for this boat with swmbo, she preferred to have safety equipment before new cushions etc.

 

[prv]

other ships and fishing boats had AIS switched off - dunno why if it is difficult to turn off and jeopardises career but there it is.

Fishing boats don't want to broadcast AIS so that they can keep their fishing patches secret.

Pete