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Old 05-01-2012, 10:06   #76
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Re: AIS experience offshore?

Quote:
Originally Posted by Patient View Post
AIS Greenhorn here, so sorry for the basic questions.

In terms of alarms. For those of you that have both Radar and AIS, do the contact alarms go off at the same time? Which has proven to be more accurate in terms of false positives? Could you walk through your setup using both or your decision to use one over the other in open ocean.

Thanks a ton!
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There are virtually no false-positive AIS alarms. (*)
A ship may trigger an alarm and subsequently change course or speed (or you may do the same), removing the alarm situation, but I wouldn't call this a false alarm.

AIS alarms are triggered when the parameters you set are met. In some units this may just be distance, and any ship inside of your alarm circle will trigger the alarm.

Many AIS systems have more sophisticated alarm parameters that take into account range, Closest Point of Approach (projected), and the time of this CPA, and possibly other factors. You will set these parameters to suit you, based on where you are sailing, the conditions, your watchstanding style, how long it's going to take you to change course if needed, and your general comfort factor.

In the open ocean, where there are likely to be only freighters, tankers, and other AIS-mandated vessels, if the visibility is good I rely on the AIS alarm (and the eyeballs-on-watch). If the visibility is poor, or I am near the coast, then the radar goes on. To conserve power I usually set it up for a timed scan. Invariably I have the sensitivity set too high and have false alarms from the waves. Over the course of a few hours I dial back the sensitivity and other adjustments until the false alarm rate is low. If I don't get the occasional false alarm I increase the sensitivity (I like to know the system is working).


* The only AIS false-alarm case I am aware of is when a vessel is feeding bad GPS data to its AIS transponder. This was a known but very rare problem, technical bulletins were issued, and the last time I saw it happen was in 2006.
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Old 05-01-2012, 11:06   #77
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Re: AIS experience offshore?

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Originally Posted by goboatingnow View Post
If I was trying to make my electronics budget stretch and I had to make priorities, AiS would be up there with VHFs and depth sounders and well before costly radar.
Also, aside from the cost of radar, the energy budget to run it full time is considerable. My little boat will only carry a 2 battery house bank. So, even if I could afford a radar, I would never be able to run it on a full-time basis. AIS can run 24/7 and not put a dent in bank. It's obvious its not a replacement for radar, but it's definitely something I'd like to have on my boat.
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Old 05-01-2012, 11:44   #78
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Re: AIS experience offshore?

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AIS is in the category of collision avoidance tools. AIS is blind to 99% of the vessels on the water. Since radar shows all of the vessels on the water, 100 times more than AIS, and only costs 10-12 times more, I'll buy radar first. AIS is a great tool, a great supplement to radar, but not the sole tool in low visibility situations. And, of course, it must be a transceiver so those AIS equipped vessels can see you.
Depends where you are. I've only kissed my radar once, in fog going down the portuguese coast. In years around the atlantic. The rest of the time (ignoring the solo aspects which are too contentious to add) , AIS does it all. The things you need to really worry about are transmitting, smaller stuff it doesn't help that much knowing their course and speed, you can't trust them anyway.
Ais is massive bang for the buck, lots of very useful instant info for the cost of some posh oillies and barely any power.

If you can afford radar you can afford both.
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Old 05-01-2012, 12:02   #79
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Re: AIS experience offshore?

From an article in Sail Magazine....

How AIS works, different receiver models, is it right for you?


Quote:
The dangers of AIS

Like any electronic gizmo, AIS can foster a sense of dependence. Itíll let you know about Class A-equipped commercial ships and Class B-equipped sailboats and powerboats; but there are plenty of boats out there that donít have AIS. The Coast Guard also warns that some commercial ships have outdated AIS software that wonít pick up Class B transmissions, so you canít be sure every ship will see you. If you treat AIS as an aid to safe sailing that backs up your own senses, rather than an oracle to be obeyed to the exclusion of all else, you should have no problems.
This closely represents my sentiment on the topic. When visibility is low and sailors leave their radar off, or don't equip their vessel with radar because of their dependency on AIS, they are putting themselves, their crew, and their vessel at great(er) risk.

As experienced sailors, we as a group should not be 'suggesting' to the noobs reading these diatribes to forego radar in favor of AIS.

AIS and radar are different tools for some what different situations. There is more that radar does that can replace AIS functionality than the other way around. Yes, AIS is cheaper. Yes, AIS is easier to use. Yes, AIS can see around corners. Yes, AIS delivers vessel data. If we're keeping score, these 4 points are negatives for radar. Yes, radar sees all vessels, not just those equipped with AIS. Yes, radar can see nav aids (markers, bouys, etc.). Yes, radar can see weather. Yes, radar can see land masses. All of the latter points are negatives for AIS. Both deliver SOG, COG, and (T)CPA.

My experience sailing in low visibility situations dictate to me that radar is the first tool in the bag and AIS is second. I personally don't care what is on your vessel as I'll see you at night regardless of what you deploy.
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Old 05-01-2012, 12:14   #80
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Quote:
Originally Posted by DotDun
From an article in Sail Magazine....

How AIS works, different receiver models, is it right for you?

This closely represents my sentiment on the topic. When visibility is low and sailors leave their radar off, or don't equip their vessel with radar because of their dependency on AIS, they are putting themselves, their crew, and their vessel at great(er) risk.

As experienced sailors, we as a group should not be 'suggesting' to the noobs reading these diatribes to forego radar in favor of AIS.

AIS and radar are different tools for some what different situations. There is more that radar does that can replace AIS functionality than the other way around. Yes, AIS is cheaper. Yes, AIS is easier to use. Yes, AIS can see around corners. Yes, AIS delivers vessel data. If we're keeping score, these 4 points are negatives for radar. Yes, radar sees all vessels, not just those equipped with AIS. Yes, radar can see nav aids (markers, bouys, etc.). Yes, radar can see weather. Yes, radar can see land masses. All of the latter points are negatives for AIS. Both deliver SOG, COG, and (T)CPA.

My experience sailing in low visibility situations dictate to me that radar is the first tool in the bag and AIS is second. I personally don't care what is on your vessel as I'll see you at night regardless of what you deploy.
Reliance on gizmos goes for radars well.
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Old 05-01-2012, 12:16   #81
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Re: AIS experience offshore?

Quote:
Originally Posted by DotDun View Post
From an article in Sail Magazine....
Quote:
If you treat AIS as an aid to safe sailing that backs up your own senses, rather than an oracle to be obeyed to the exclusion of all else, you should have no problems.
Doubt if anyone who can't figure that out on their own is going to get much sense out of a radar set

Quote:
As experienced sailors, we as a group should not be 'suggesting' to the noobs reading these diatribes to forego radar in favor of AIS.
Has anyone said that? might have missed.

If you have an idiot skipper who is too stupid to figure out when to be a bit scared out there then telling him not to have ais isn't going to change much.
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Old 05-01-2012, 13:12   #82
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Re: AIS experience offshore?

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Originally Posted by conachair View Post
Has anyone said that? might have missed.
Quote:
Originally Posted by colemj View Post
Bang for buck, definitely above radar.
Quote:
Originally Posted by goboatingnow View Post
What was meant that inn terms of benefit against cost it ranks above radar and I'd agree. On a budget conscious fit out I'd pay for it before radar.

Dave
Quote:
Originally Posted by goboatingnow View Post
AIS is not a simple supplement to radar. It is a collision avoidance, situational awareness tool in its own right.
Quote:
Originally Posted by colemj View Post
So, in my opinion, the AIS gives a lot more cost/benefit than radar.
Quote:
Originally Posted by goboatingnow View Post
If I was trying to make my electronics budget stretch and I had to make priorities, AiS would be up there with VHFs and depth sounders and well before costly radar.
Dave has stated that having to chose just one, he would go with AIS before radar. Mark has stated AIS is better bang for buck than radar.

Noobs will take this and forego radar and trust AIS as 'the oracle'.

from the free dictionary, a definition:
Quote:
bang for the buck
value for the money spent; excitement for the money spent; a favorable cost-to-benefit ratio.
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Old 05-01-2012, 13:39   #83
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Re: AIS experience offshore?

Do we have to have this exact same argument every time AIS is being discussed?

  • AIS is a useful tool.
  • RADAR is a useful tool that costs approximately 10x an AIS setup.
  • One does not replace the other.
  • RADAR does many things well and is highly recommended.
  • AIS will only show AIS-transmitting objects, nothing else.
  • Neither one is an absolute requirement.
  • If you can't afford RADAR, you are still allowed to go sailing.
  • If you can afford AIS, it's a nice thing to have.
  • If you want both, get both.
  • Whatever fancy gear you have, you still need to look around ad keep a proper watch, you need to practice, you need to remember that electronics can fail.

Does that just about cover it?
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Old 05-01-2012, 13:48   #84
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Quote:
Originally Posted by Paul Elliott
Do we have to have this exact same argument every time AIS is being discussed?

[*]AIS is a useful tool.[*]RADAR is a useful tool that costs approximately 10x an AIS setup.[*] One does not replace the other.[*] RADAR does many things well and is highly recommended.[*] AIS will only show AIS-transmitting objects, nothing else.[*] Neither one is an absolute requirement.[*] If you can't afford RADAR, you are still allowed to go sailing.[*] If you can afford AIS, it's a nice thing to have.[*] If you want both, get both.[*] Whatever fancy gear you have, you still need to look around ad keep a proper watch, you need to practice, you need to remember that electronics can fail.


Does that just about cover it?
The funny thing is, as a noob, I don't need anyone to explain this

Makes me wonder how anyone ever got started cruising without such explicit instructions.
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Old 05-01-2012, 14:36   #85
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Re: AIS Experience Offshore?

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The funny thing is, as a noob, I don't need anyone to explain this

Makes me wonder how anyone ever got started cruising without such explicit instructions.
You crazy fool!!

You mean you just go and do things without consulting "those who know the way it should be done" ?

Though this thread has been interesting, seems to be an agreement that offshore, chances are, the big boys willl be transmitting.

Which is nice
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Old 05-01-2012, 15:17   #86
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Re: AIS Experience Offshore?

Two things for AIS, 1. Biggest threat offshore, (remember OP), getting run over by a big freighter, If you are transmitting AIS he can see you, even if his radar doesn't. You can see him and his course, speed, callsign, dsc code, and size, in plenty of time for both of you to arrange passing.

2. In tight quarters you can see who is coming around corners you can't see with radar, (yes there will be some boats that aren't transmitting AIS, but you can't see them visually or with radar either). And the ones who are too big to evade you, WILL be transmitting. I would not go down the ICW without one ever again, for this reason.
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Old 05-01-2012, 16:31   #87
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Re: AIS Experience Offshore?

I run AIS always dock to dock and all night on the hook. The radar is on for night and fog. We replaced our conventional radar with Broadband to get better short range resolution, lower power footprint. At less than 9 miles/hour, 15 miles is enough range. In our marina, it can pick out and overlay all of the empty slips and show every piling. Before radar, we stayed put. Given the choice, I will still not go out in fog. We do cross Lake Michigan. Easily 99% of boats more than 10 miles off shore are commercial. They can choose to ignore you on their radar and may even ignore your radio hailing. They cannot ignore your AIS transponder and they will almost always answer the radio when you hail by name or DSC their MMSI. Just another tool, less costly than a good offshore PFD and saves your behind way more often. If I had to put my instruments & radios in order of importance; compass, depth, GPS handheld, AIS, wind speed; wind direction, VHS, chartplotter, radar, bathemetric scanner, SSB, FM. This will probably change as we move out the St Lawrence in a couple of years as our venue changes. If i was forced to run in fog often, the Radar would move up the list for sure.

AIS importance is dependent a lot on how you sail, however, I would not consider off-shore cruising without it.

Other goodies. Nearly free regarding power use including anchor watch. On a transit lasst summer from Manistee to Muskegon we were allerted by the AIS that there were two Tall Ships in Ludington harbor. We knew the boat names from the year before where we all met in Green Bay. We diverted toward shore and watched our friends wage a cannon battle in the harbor. Pretty cool. Later, on the continuation south, we picked up a string of CG vessels headed straight at us. They were returnig to stations following the Grand Haven Coast Guard Festival. Nice to have a 20 mile warning on a mess 'o Coasties. Had some nice greetings from some of them.
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Old 05-01-2012, 16:44   #88
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Re: AIS Experience Offshore?

I was easily able to integrate it with CM93 and show the positions on my laptop. I can see these from the helm. It works well that way. I will try and hook it up to Open CPN. I used it coming up the coast of Baja and only spotted a few ships till I reached Ensenada. From there I was overwhelmed having tens of ships in the 20 mile range so I had to narrow down the field to 5 miles. Overall I liked it. I bought the Standard Horizon radio that has the AIS in it in 2009.
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Old 05-01-2012, 16:55   #89
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Re: AIS experience offshore?

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Originally Posted by DotDun View Post
Dave has stated that having to chose just one, he would go with AIS before radar. Mark has stated AIS is better bang for buck than radar.

Noobs will take this and forego radar and trust AIS as 'the oracle'.

from the free dictionary, a definition:
DotDun, in what fantasy land did my comments say, or imply, that people should forego radar and trust AIS as "the oracle"? Really, your statement pisses me off and I want you to know that. You asked me to qualify what I meant by bang for buck and I did. I was very careful to qualify it as a personal opinion of relative value divided by a fact of cost. You obviously don't like my opinion that a $180 AIS receiver delivers a lot of value for the price - more so than radar given its cost, and that is fine. But you do not have the right to twist into it anything else, let alone publish your own misinterpretation of what I said. I said nothing about getting one over the other or about AIS being an "oracle". I merely pointed out a recent situation where AIS was more helpful to us than radar. If one can afford radar, one will almost certainly have a $200 AIS (or better). If one can't afford radar, one can still get a $200 AIS. An interesting point is that many countries are requiring AIS on board all vessels, but not radar. You really have a hair up your butt on this one.

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Old 05-01-2012, 21:59   #90
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Re: AIS experience offshore?

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DotDun, in what fantasy land did my comments say, or imply, that people should forego radar and trust AIS as "the oracle"? Really, your statement pisses me off and I want you to know that. You asked me to qualify what I meant by bang for buck and I did. I was very careful to qualify it as a personal opinion of relative value divided by a fact of cost. You obviously don't like my opinion that a $180 AIS receiver delivers a lot of value for the price - more so than radar given its cost, and that is fine. But you do not have the right to twist into it anything else, let alone publish your own misinterpretation of what I said. I said nothing about getting one over the other or about AIS being an "oracle". I merely pointed out a recent situation where AIS was more helpful to us than radar. If one can afford radar, one will almost certainly have a $200 AIS (or better). If one can't afford radar, one can still get a $200 AIS.
Mark,

Sorry that my interpretation of your statements pissed you off. Like you, my conclusion of your statements, are my opinion.

I believe others may draw the same conclusions reading posts in this thread as I, especially those with little or no experience.

I am curious that if your goal was truly to express your satisfaction with 'bang for buck' buying an AIS receiver why you chose to compare it with radar? Why not compare it to a bilge pump? Or a battery charger? At least everyone would understand you meant it as a truly financial comparison.

When I pushed you further, you stated in post #74:

Quote:
Originally Posted by colemj View Post
100% of commercial traffic has AIS, so you are left with smaller fishing boats and recreational boating. I'm not too worried about recreational boats because they are small and moving at 4-7kts - I see them well before they are a problem and can avoid one within a hundred feet with a 10 second turn of the wheel (it never comes to this of course - I'm just making an example). So the smaller fishing boats are the problem. Fortunately, they are almost all coastal and most of them lit up with floodlights.
My interpretation of this post is that it is your opinion that any vessel not sending AIS is trivial as you can either see their lights or are able to out maneuver them as they are slow moving. Yes, I used that as fuel for claiming that you value AIS higher than radar because you presented it that way.

Maybe in your part of the world, that works. You obviously have never experienced the 50' 20T sport fishing boat at 4am 50 miles offshore running 30kph to get to his favorite fishing spot by daylight. Or shared a squall with 12+ fishing trawlers. Not a word about the go fast boats around Miami that run 60kph in good visibility and bad. No AIS on these vessels.

Also as you can see, I didn't 'pick on' just you. I also took Dave's statements to fuel my thesis. Then I corroborated it with a Sail Magazine article where the author has the same fear I do - over exuberance about AIS.

Quote:
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An interesting point is that many countries are requiring AIS on board all vessels, but not radar.
I'll bet the requirement is a transceiver, not a receiver. (psst, I already have mine! )

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You really have a hair up your butt on this one.
Yep! When those that should know the difference don't give a full or fair comparison, I'll point it out.
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