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Old 31-08-2013, 08:17   #106
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Re: AIS: A Creepy Experience.

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Originally Posted by wxman View Post
Many of you have already said this, but one needs to really figure out the risk assessment for each of the mentioned risks.
It seems to me that getting run over by a large ship should be the worst case. With an AIS transceiver that is far less likely to happen, as they will see. Also, when you have the shipís name, they will respond on the radio if you call them.
IMHO If you are more concerned with people knowing where you are, then getting run over, thatís a whole different discussion.

Richard
The reality that I've seen with collision avoidance and AIS is that because so much detail is available at such a great distance it removes a lot of the guess work. So imagine the scenario of a container ship ten miles away in crap nighttime visibility that, unadjusted, you will pass within 1/8 mile of (way too close for a ship's comfort).

With visual (and non-fancy radar system) you will spend ten minutes studying it, trying to determine it's course, trying to determine it's speed, and looking for constant-bearing-decreasing-range scenarios. The bowlight will be dipping up and down in the swells until you're within a couple miles of an unknown-length vessel.

With AIS, ~25 miles out you'll know exactly where it is, how close you'll get, and if you're transmitting as well the ship knows the same. A minor two degree turn to starboard for both of you will open up the distance and you can go back to reading your book.

Again, I'm not advocating the ignorance of seamanship and manually spotting collision conditions but AIS allows you to turn a lot of the middle-of-the-night-bad-weather shenanigans into a thirty second course adjustment that probably doesn't even require a sail trim.
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Old 31-08-2013, 09:27   #107
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Re: AIS: A Creepy Experience.

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Originally Posted by Paul L View Post
AIS is a great tool in your electronics and manual arsenal. It allows you to very quickly determine CPA and TCPA of transmitting ships. This covers the vast majority of large ships -- any ship over 300 tons that travels internationally, excepting military, is required to use it. If you don't want to transmit your position, don't. I have my AIS TX on when we are on passage or in reduced visibility, otherwise I usually leave it off.
Its just a tool, and clearly not a 100% - like all other nav tools.
I agree with you, Paul. It's a tool. In terms of it being creepy, I'm not really sure how it is more or less creepy than following a target visually or on radar.
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Old 31-08-2013, 10:10   #108
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Re: AIS: A Creepy Experience.

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Originally Posted by rebel heart View Post
The reality that I've seen with collision avoidance and AIS is that because so much detail is available at such a great distance it removes a lot of the guess work. So imagine the scenario of a container ship ten miles away in crap nighttime visibility that, unadjusted, you will pass within 1/8 mile of (way too close for a ship's comfort).

With visual (and non-fancy radar system) you will spend ten minutes studying it, trying to determine it's course, trying to determine it's speed, and looking for constant-bearing-decreasing-range scenarios. The bowlight will be dipping up and down in the swells until you're within a couple miles of an unknown-length vessel.

With AIS, ~25 miles out you'll know exactly where it is, how close you'll get, and if you're transmitting as well the ship knows the same. A minor two degree turn to starboard for both of you will open up the distance and you can go back to reading your book.

Again, I'm not advocating the ignorance of seamanship and manually spotting collision conditions but AIS allows you to turn a lot of the middle-of-the-night-bad-weather shenanigans into a thirty second course adjustment that probably doesn't even require a sail trim.
Nice summary, Eric. I agree completely with this assessment.

Our experience on the east coast of Oz and Coral and Tasman seas is that 100% of the merchant vessels are transmitting while under way. That is, every one that we have seen visually or on radar have done so. Very few fishing vessels do so, and only a small fraction of yachts, so general watchkeeping is still a priority, but the decision making process is materially aided by the AIS data.

Cheers,

Jim
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Old 31-08-2013, 10:54   #109
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Re: AIS: A Creepy Experience.

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And now here's the creepy part... One day, we left port where some folks we'd met the night before remained for an extra day... we didn't know their itinerary. Two days out, my wife noticed their AIS transmission (via boat name) on our plotter as the vessel two miles ahead of us, so it remained near the top of the list the entire day. Each time I went below to check other things, I couldn't help but notice what our friends were up to... their movements, speed, location within 15 feet, vessel type and size. I knew when they were underway, when they were in the marina looking for a berth and when and where they had decided to anchor instead. It just so happened, that we had planned several days earlier to anchor in the very same cove which they had also chosen. We weren't trying to follow them, but after seeing how easy it would be for the wrong people to do the same, we decided not to improve our system with a transponder and shared the experience with our new friends.
While your points are valid, AIS does not excuse us from keeping a proper watch by eye, or by eye and RADAR if that's part of the nav tools available. I was under the impression that most commercial vessels were supposed to transmit on AIS, but perhaps this is either a) grandfathered, or b) a technical problem. There are clearly good reasons from a criminal point of view to not transmit, but if a country's coast guard picked up a 200 foot target approaching land that didn't have an AIS/MMSI/IMO number transmitting, I suspect it would attract their interest.

As for your friends, I don't find it creepy at all. Cellphones, as has been pointed out, can be loaded with "snooper apps" invisible to the user that report via internal GPS or proximity to cell towers the phone's location. The cops can narrow it down even without such apps. AIS is no different...except that you can turn off the transmitter.

Would I do this on coastal cruising? No, if I was solo (because it's like a SPOT tracker to rescuers if I fall off the boat and forget to bring my bag of breadcrumbs), but yes, were we well crewed, as there is no compelling reason to announce our presence to other boats or ships on, say, a clear, sunny day.

At night, circumstances change. In fog, at night...AIS is probably better than RADAR if you have a fibreglass boat, because it transmits (usually) from the mast top, and your plastic hull behind a series of waves is a poor target for a ship's radar.

Offshore, yes: I want to be seen as well as to see, and AIS is frequently better than RADAR here as well for picking up ships barely at the horizon...as seen from 50 feet up!

Offshore entering the Red Sea or certain straits near Indonesia, or the Gulf of Benin? Probably not. Probably not nav lights, either, but doubled eyeballs on deck.

So the solution is to figure out if your kind of sailing is enhanced by being seen, and then to find the OFF button if the answer is, "yes, but not all the time". Frankly, less clutter is better: who really needs to know you are docked?
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Old 31-08-2013, 11:02   #110
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Re: AIS: A Creepy Experience.

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Originally Posted by Kenomac View Post
An issue I didn't bring up on my initial post, which I'll bring up now, is a concern for how many cruisers I've spoken with recently who now have an over confidence in their AIS system and have chosen to get rid of radar or to not have it installed on a new boat.... preferring instead to rely exclusively on AIS without seeing the possible problems, like seeing other vessels who aren't transmitting.

I agree with you, AIS is a very helpful technology.... But for now, I'll choose to only receive rather than to transmit.
Fine, but anyone who doesn't realize that AIS enhanced and complements RADAR (I can't wait for AIS-equipped buoyage to become more widespread) also probably can't make a sandwich that isn't open-faced.

RADAR and AIS represent a Venn diagram of watchkeeping at a distance. The reason to keep your RADAR is to get an AIS...because AIS catches either ships and AIS-transmitting objects too far for RADAR, or it helps to sort a bunch of blobs with names and real-time position tracking not calculated on your boat, but from the transmitting boat.

You can buy a Vesper unit and the cheapest sort of basic radar and have more comprehensive watchkeeping than you would have with a commercial radar of the latest tech alone.
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Old 31-08-2013, 11:11   #111
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Re: AIS: A Creepy Experience.

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Since there is no privacy anymore, we should all run through the streets naked.
I have no wish to startle the horses.
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Old 31-08-2013, 11:16   #112
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Re: AIS: A Creepy Experience.

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Originally Posted by s/v Jedi View Post
When you only receive half the boats and ships around you, I find it more probable that your receiver only gets one of the two channels somehow (or it is an old/cheap one that could only do one channel or gets overloaded with more than 5 targets) rather than that the other half of boats and ships don't transmit AIS.
Even a single-channel receiver should pick up all the boats within range, it will just take twice as long. AIS transponders transmit on two channels, alternating from one to the other with each transmission. This is to make the system tolerant to interference or equipment faults.

The "dynamic" messages (position, course, speed, etc) are sent frequently enough when a vessel is underway that you may not notice the delay with the single-channel receiver. The "static" messages (name, callsign, vessel dimensions, cargo type, navigational status, etc) are sent at six-minute intervals. With a single-channel receiver it might take twelve minutes to get this information, or longer if the radio reception is marginal.

Some of the single-channel receivers switch channels at some rate, and in some cases this can make the "missed transmission" problem even worse. But even so, the message should eventually be received. I do recommend a dual-channel receiver, since one of the useful features of AIS is to have a ship's name for VHF calls. I want to get this information ASAP. Transponders all have dual-channel receivers.

If you use your VHF for a DSC call to the ship, you don't have to wait for the name to show up -- the MMSI (used as a DSC "phone number") is included in both dynamic and static AIS messages.
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Old 31-08-2013, 12:55   #113
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Re: AIS: A Creepy Experience.

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Originally Posted by MarkJ View Post
Even better... both parties, but especially the ships, have the AIS digitally recorded so that if theres any problem the court is gunna know about it.

This information is recorded in both boats (if you have a SD card in) but also every other ship in the coverage area. Witnesses!


Mark
Ships do have voyage data recorders which do record AIS information (among other parameters). Also, most, if not, all, ECDIS/ECS programs have their own recording/playback features that are automatically saved. Since the vast majority of these systems are integrated with the AIS system, they also become quasi AIS recorders.

Also, to the OP, I very much doubt you encountered large ships transiting the US East Coast without transmitting AIS. I've been sailing large commercial vessels including ships and tugs for quite awhile now all over the US and overseas (including the Med and Asia) and have never once encountered a vessel that wasn't transmitting when it should have been. Crews have no reason or incentive to stop transmitting (why would they?) except for in very extreme circumstances, none of which are likely applicable in North American waters. A malfunctioning or weakly transmitting unit would certainly be noticed the first time that vessel sailed into a VTS area. Now I'm not saying your receiver wasn't picking them up but the issue was probably on your end.

Fishing vessels and the occasional tugboat are another matter...
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Old 31-08-2013, 14:28   #114
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Re: AIS: A Creepy Experience.

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Originally Posted by Watermann View Post
Also, to the OP, I very much doubt you encountered large ships transiting the US East Coast without transmitting AIS. I've been sailing large commercial vessels including ships and tugs for quite awhile now all over the US and overseas (including the Med and Asia) and have never once encountered a vessel that wasn't transmitting when it should have been. Now I'm not saying your receiver wasn't picking them up but the issue was probably on your end.

Fishing vessels and the occasional tugboat are another matter...
Our AIS receiver is working just fine. We're currently in the Med, Southern Spain to be specific and encountered all three non-transmitting ships including a medium-large size container ship and two super yachts just north of Mallorca. We watched and tracked them, then altered our course to avoid being run over. All other vessels with AIS transmissions were on the screen during that same time.

The fishing boats around here hardly ever broadcast an AIS signal, especially the smaller ones. Just yesterday a fairly large fishing boat, maybe 100ft towing a net.... no AIS. And later he passed us on his way into port.... no AIS, meanwhile we were picking up signals from even some of the smaller sailboats and a few powerboats.

We even went so far as to have our VHF radio and antenna checked out in Mallorca following the occurrence... everything OK according to the electrician.

Ken
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Old 31-08-2013, 15:25   #115
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Re: AIS: A Creepy Experience.

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Originally Posted by Kenomac View Post
Our AIS receiver is working just fine. We're currently in the Med, Southern Spain to be specific and encountered all three non-transmitting ships including a medium-large size container ship and two super yachts just north of Mallorca.
They don't need to have AIS in Spain because their government isn't spying/watching/listening to their every move.
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Old 31-08-2013, 21:22   #116
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Re: AIS: A Creepy Experience.

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Originally Posted by rebel heart View Post
The reality that I've seen with collision avoidance and AIS is that because so much detail is available at such a great distance it removes a lot of the guess work. So imagine the scenario of a container ship ten miles away in crap nighttime visibility that, unadjusted, you will pass within 1/8 mile of (way too close for a ship's comfort).

With visual (and non-fancy radar system) you will spend ten minutes studying it, trying to determine it's course, trying to determine it's speed, and looking for constant-bearing-decreasing-range scenarios. The bowlight will be dipping up and down in the swells until you're within a couple miles of an unknown-length vessel.

With AIS, ~25 miles out you'll know exactly where it is, how close you'll get, and if you're transmitting as well the ship knows the same. A minor two degree turn to starboard for both of you will open up the distance and you can go back to reading your book.

Again, I'm not advocating the ignorance of seamanship and manually spotting collision conditions but AIS allows you to turn a lot of the middle-of-the-night-bad-weather shenanigans into a thirty second course adjustment that probably doesn't even require a sail trim
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Originally Posted by Jim Cate View Post
Nice summary, Eric. I agree completely with this assessment.

Our experience on the east coast of Oz and Coral and Tasman seas is that 100% of the merchant vessels are transmitting while under way. That is, every one that we have seen visually or on radar have done so. Very few fishing vessels do so, and only a small fraction of yachts, so general watchkeeping is still a priority, but the decision making process is materially aided by the AIS data.

Cheers,

Jim
I agree with Eric and Jim.

I have my AIS alarm set for CPAs under 2 miles and a TCPA less than 45 minutes. On many occasions, I have seen ships make course early course adjustments based upon my transmitted AIS data. Since my AIS is receiving signals at ~65 ft it has a significantly better reception range than my 25 ft high radar antenna and far better than my mark one eyeball! (It also increases the range at which I can be seen.) In fact I have very had very few instances where MARPA, especially in a high sea states, gave CPA information that was as reliable as my AIS.

I have had a few instances where there has been superstructure blanking of an AIS signal resulting in far shorter than normal ranges for shipping targets but they are few and far between. It is far more common to have very short ranges from sailboats with poorly mounted antennas (on the rail or arch) that are not propagating well in all directions. I have had many instances where I have made a course adjustment base on a visual sighting of a sailboat and then receive their AIS signal only when we are less than 2 miles apart!

Knowing when and where you will see other traffic appear makes watch keeping not only easier, but it also gives you more time to concentrate about the non- AIS targets that are out there. There is less need to spend the 10 minutes or more assessing a target on your port bow while missing another target converging from the starboard beam!
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Old 31-08-2013, 21:27   #117
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Re: AIS: A Creepy Experience.

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They don't need to have AIS in Spain because their government isn't spying/watching/listening to their every move.
Are the chemtrails sites down?
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Old 01-09-2013, 05:57   #118
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Re: AIS: A Creepy Experience.

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Originally Posted by LJH View Post
I have my AIS alarm set for CPAs under 2 miles and a TCPA less than 45 minutes.
Just as a test try setting your CPA alarm at .9NM.
Many ships Captains and/or Company policy is to keep the CPA no less than 1NM or 2NM. So a ship who comes within that is in deep do-do with the boss.
I find many ships deviating no matter the colreg rule to keep a CPA of greater than 1NM or 2NM.


If everyone stays outside your CPA you will have a much more relaxing watch


Mark
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Old 01-09-2013, 07:09   #119
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Re: AIS: A Creepy Experience.

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Originally Posted by Kenomac View Post
Our AIS receiver is working just fine. We're currently in the Med, Southern Spain to be specific and encountered all three non-transmitting ships including a medium-large size container ship and two super yachts just north of Mallorca. We watched and tracked them, then altered our course to avoid being run over. All other vessels with AIS transmissions were on the screen during that same time.

The fishing boats around here hardly ever broadcast an AIS signal, especially the smaller ones. Just yesterday a fairly large fishing boat, maybe 100ft towing a net.... no AIS. And later he passed us on his way into port.... no AIS, meanwhile we were picking up signals from even some of the smaller sailboats and a few powerboats.

We even went so far as to have our VHF radio and antenna checked out in Mallorca following the occurrence... everything OK according to the electrician.

Ken
Just be aware , that super yachts are not SOLAS compliant vessels and do not require compulsory AIS. Mind you most Ive met do have it now.

The EU has extended AIS to fishing vessels effective I believe in 2015. So we should see more and more of those types of vessels include in the AIS-sphere

dave
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Old 01-09-2013, 08:40   #120
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Re: AIS: A Creepy Experience.

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Just be aware , that super yachts are not SOLAS compliant vessels and do not require compulsory AIS. Mind you most Ive met do have it now.

The EU has extended AIS to fishing vessels effective I believe in 2015. So we should see more and more of those types of vessels include in the AIS-sphere

dave

Just fyi . . . . If commercial classed they are SOLAS, and most are commercial classed for tax reasons.
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