Thoughts about AIS

[Dockhead]

Originally Posted by poiu

Having identified the collision danger and where you are the stand on vessel and the ship is doing nothing there comes the difficult decision - shall I wait a few minutes for him to move as surely he will or should I turn anyway. After a few more minutes it becomes urgent. I'd better call him and ask him for his intentions or maybe I should turn anyway. Then comes the fumble with tapping through clumsy DSC menus and finding, noting and entering the code and waiting whilst the watch officer puts his coffee down. By that time he has done nothing and it really is necessary for someone to take some kind of action....

What would be really useful is a way of hitting the icon on the screen and making a DSC call instantly. Is there a way of doing this?

I agree, but knowing the name of the ship is already 90% of the battle. If you don't feel like you have time to make a DSC call, you can just call him by name on 16.

[monte]

VHF isn't really recommended for collision avoicance
At times it may be a useful tool, but not one I would rely on.
An interesting collision report where both AIS and VHF were used.

http://www.maib.gov.uk/cms_resources...ery_Report.pdf

extract "While it is likely that ACX Hibiscus’s chief officer was adversely affected by fatigue,
there are many other potential reasons why an OOW may not respond to a VHF call.
These might include: other, more pressing work; faulty equipment; not understanding
the language used during transmission; or even that the bridge is not manned.
It is acknowledged that VHF radio calls are routinely used by OOWs to advise other
vessels of their intentions and to request clarification of another vessel’s movements.
However, this method cannot be relied on for collision avoidance, and OOWs must
not allow the use of VHF radio to delay them from taking action.
The lessons learnt from this accident should serve as a timely reminder of the risks
of using VHF radio for collision avoidance, as highlighted in MGN 324 (M+F)."

[IslandHopper]

Originally Posted by Dockhead

Note also that in areas of heavy traffic, like where I sail, ships most often simply ignore VHF calls from yachts. They don't especially want to hear our stupid blather, and they don't especially want to discuss what should be obvious, and only the most polite and patient of them is really willing to talk us through a crossing on the radio. What they really want is for us to follow the COLREGS and avoid any sudden, unexpected maneuvers. This confirmed in dozens of conversations with professional mariners.

This has become such a problem around the Great Barrier Reef that some pilots have a standard response to yotties incessant questions regarding intentions.

"We shall be observing Colregs and we expect you to be doing the same, if you do not understand Colregs then keep well clear of this vessel".....

[colemj]

Originally Posted by poiu

What would be really useful is a way of hitting the icon on the screen and making a DSC call instantly. Is there a way of doing this?

Our VHF radio has an AIS receiver built in, so one only needs to highlight the ship on its screen and press "call".

Some chartplotters also have this feature, but I believe they all require that brand's radio to work.

Vespar stand alone units have this feature (according to their advertisement), but I don't know how it is implemented with radios, or if the radios have to be specific brands.

We have found hailing on ch16 to be a waste of time anymore. Ships seem to often ignore the call, or it gets lost in the background, or the volume is low, or calling them by "ship at approximately XX coordinates" isn't specific enough, or etc.

A direct DSC call, however, rings directly on the bridge and is usually answered quickly.

Mark

[colemj]

Originally Posted by IslandHopper

This has become such a problem around the Great Barrier Reef that some pilots have a standard response to yotties incessant questions regarding intentions.

"We shall be observing Colregs and we expect you to be doing the same, if you do not understand Colregs then keep well clear of this vessel".....

Yes, it is too bad, but we know many, many cruisers who call every ship they see regardless of crossing situation or not and ask both what the ship's intentions are and if they can be seen on the ship's radar. They actually talk about it in groups as if it was a badge for how many ships they contacted during a passage. I think many believe it is actually a good practice to contact any ship they see. It gets simply ridiculous around major ports and shipping lanes.

Calling a ship to negotiate a crossing should only be done if one finds themselves in a impractical situation where maneuvering is difficult and one is the stand-on vessel. And only then if it is apparent that the burdened ship has somehow misread the situation. This has occurred to us only once in the past 6 years.

Mark

[poiu]

Originally Posted by colemj

Our VHF radio has an AIS receiver built in, so one only needs to highlight the ship on its screen and press "call".

Some chartplotters also have this feature, but I believe they all require that brand's radio to work.

Vespar stand alone units have this feature (according to their advertisement), but I don't know how it is implemented with radios, or if the radios have to be specific brands.

We have found hailing on ch16 to be a waste of time anymore. Ships seem to often ignore the call, or it gets lost in the background, or the volume is low, or calling them by "ship at approximately XX coordinates" isn't specific enough, or etc.

A direct DSC call, however, rings directly on the bridge and is usually answered quickly.

Mark

Which model VHF does this? I was looking at the Simrad as that has a great remote handset and AIS, but it doesn't seem to have the auto dial.

I suspect a lot of bridge officers turn down channel 16 as there is often so much rubbish on air it is pretty dysfunctional.

[ka4wja]

Mark is correct here....and he beat me to the answer...

Originally Posted by colemj

Our VHF radio has an AIS receiver built in, so one only needs to highlight the ship on its screen and press "call".


Some chartplotters also have this feature, but I believe they all require that brand's radio to work.
Most (all?) NMEA2000 VHF radios and AIS systems should allow this seamless procedure....
Vespar stand alone units have this feature (according to their advertisement), but I don't know how it is implemented with radios, or if the radios have to be specific brands.
Most (all?) NMEA2000 VHF radios and AIS systems should allow this seamless procedure....but you may wish to contact Vesper (or he may chime in here), for any radios that they have tried this with...


We have found hailing on ch16 to be a waste of time anymore. Ships seem to often ignore the call, or it gets lost in the background, or the volume is low, or calling them by "ship at approximately XX coordinates" isn't specific enough, or etc.
Yes, you will usually never get an answer from a Ch. 16 call...as nobody is listening...
(although some have luck hailing on Ch. 13, used for bridge-to-bridge comms, DSC is still your best bet...)

A direct DSC call, however, rings directly on the bridge and is usually answered quickly.

Mark

As for hailing every ship....that must be a rather new "game"???
I've not heard of it....but, unfortunately it doesn't surprise me!!

(FYI, in years long since passed....such as the 1970's....while on a long passage, we used to hail a ship at sea in order to confirm weather forecasts and, if it had been cloudy, to verify our position....remember this was back in the days before GPS....and while on an Atlantic crossing we did have the old US Navy WeFax broadcasts, sometimes we didn't get the latest ones, and we always were treated to the ship's radio officer / exec officer giving us a great weather briefing....and many times even the captain would talk to us for quite some time....but that was 40+ years ago!!! and there were few sailing beyond the sight of land, let alone across oceans, and ship's crews were more "seasoned" back then as well, so they actually wanted to talk to a sailboat out there on a passage....
But, this new "game"....sounds ridiculous!!)


Fair winds...

John
s/v Annie Laurie

[colemj]

Originally Posted by poiu

Which model VHF does this? I was looking at the Simrad as that has a great remote handset and AIS, but it doesn't seem to have the auto dial.

Ours is the Standard Horizon Matrix AIS. I would be surprised if the Simrad one left out that simple function.

Mark

[goboatingnow]

I think those people that don't have to deal with some of the unique situations typical of high density traffic and more importantly high speed traffic , these areas are typical in certain pinch points around the Northern European coast.

My own personal experiences, mostly predate having AIS

couple of things

The Wakhuna accident , was in FOG. the running lights weren't visible and the whole process was done by radar. In was hindered by having the radar only visible below and hence details had to be relayed by the radar watch keeper.

The primary issue was that Wakhuna had entered the " cone of error", i.e. the radar plot of the approaching vessel simply was not accurate enough to determine whether he was already across or yet to cross the oncoming vessel. This is a very common issue and anyone with a predicated COG vector ship on ( or MARPA ) vector, will readily see that in a seaway on a small yacht they can be almost useless.

The failings on the bridge of the Nedloyd were much smaller, ground referenced ARPA is actually a common setting.

the only saving grace with AIS, is at least the bigger ships prediction is based on his data not yours.

Today , I use COG predictive vectors. I usually set them to max and equal time.

I then use the following logic

If they don't cross and my vector end before their vectors, i will pass astern, a simple rough proportional calculation will give you roughly where you will pass.

if they cross, again I do a simple proportional calculation ( by eye usually), if I'm ½ and he's ½ then we have a problem houston, if the proportions are skewed I can usually determine quickly if Im across or not at CPA.

Often I turn off all the alarms, cause otherwise its info overload. MARPA , I don't use at all in these situations, I simply don't trust it.

I agree crossing the TSS in the channel, is a butt puckering exercise, AT night its even worse and in fog, I just pray a lot. personally I try to cross the channel , outside the TSS areas.

you get the same problem sometime off Ushant, land ends TSS and approaches to Gib. not as bad though.

I agree with Pelagic, if you transmit AIS data that you are a sailing vessel, big ships are like elephants and yachts, mice.

Calling up bridges in these situations is just laughable.

dave

[Dockhead]

Originally Posted by goboatingnow

I think those people that don't have to deal with some of the unique situations typical of high density traffic and more importantly high speed traffic , these areas are typical in certain pinch points around the Northern European coast.

My own personal experiences, mostly predate having AIS

couple of things

The Wakhuna accident , was in FOG. the running lights weren't visible and the whole process was done by radar. In was hindered by having the radar only visible below and hence details had to be relayed by the radar watch keeper.

The primary issue was that Wakhuna had entered the " cone of error", i.e. the radar plot of the approaching vessel simply was not accurate enough to determine whether he was already across or yet to cross the oncoming vessel. This is a very common issue and anyone with a predicated COG vector ship on ( or MARPA ) vector, will readily see that in a seaway on a small yacht they can be almost useless.

The failings on the bridge of the Nedloyd were much smaller, ground referenced ARPA is actually a common setting.

the only saving grace with AIS, is at least the bigger ships prediction is based on his data not yours.

Today , I use COG predictive vectors. I usually set them to max and equal time.

I then use the following logic

If they don't cross and my vector end before their vectors, i will pass astern, a simple rough proportional calculation will give you roughly where you will pass.

if they cross, again I do a simple proportional calculation ( by eye usually), if I'm ½ and he's ½ then we have a problem houston, if the proportions are skewed I can usually determine quickly if Im across or not at CPA.

Often I turn off all the alarms, cause otherwise its info overload. MARPA , I don't use at all in these situations, I simply don't trust it.

I agree crossing the TSS in the channel, is a butt puckering exercise, AT night its even worse and in fog, I just pray a lot. personally I try to cross the channel , outside the TSS areas.

you get the same problem sometime off Ushant, land ends TSS and approaches to Gib. not as bad though.

I agree with Pelagic, if you transmit AIS data that you are a sailing vessel, big ships are like elephants and yachts, mice.

Calling up bridges in these situations is just laughable.

dave

Indeed -- and no one knows what the "cone of error" is for AIS, which I think everyone assumes is accurate to a centimeter. That part of the Wahkuna report which discusses those factors which increase the cone of errors is really interesting and is really worth noting.


As to crossing the Channel at night -- I've always, even before AIS, found it rather easier on a clear night than in the daytime. I have always found that it's easier to understand the aspect of ships you see by their lights, than from their shapes seen in daylight.

Fog terrifies me inshore or, God forbid, in harbors, but I am not that much afraid of fog when out of sight of land, at least not since AIS. I put someone else on the helm and sit at the nav table. In the middle of the Channel there are few dangerous objects not transmitting AIS. I always just avoid any radar target not transmitting AIS -- it's not a ship, so you're not going to have a regular crossing with it, so just get out of the way. I put MARPA on it not to make a precise CPA calculation (which MARPA can't), but to know whether it's moving or not, and how, and roughly how fast, which is usually enough information to know more or less what it is. I like the way MARPA targets are displayed on my Zeus -- a trail of dots are left where the target was painted every time, with an arrow and predicted COG line.


Your technique of using COG extension lines is really interesting. I'm going to re-read and study it.

[colemj]

Originally Posted by Dockhead

Indeed -- and no one knows what the "cone of error" is for AIS, which I think everyone assumes is accurate to a centimeter.

Your technique of using COG extension lines is really interesting. I'm going to re-read and study it.

Come on DH - you keep telling me you don't say things like this, but you keep saying them! Can we agree to stop assuming everyone but ourselves are stupid? And agree that there is no general problem using any technology? And agree that there will always be a few stupid people whether they are using a technology or not?

If so, then these discussions will be more fruitful. If not, then please point to all of the boats being run down from using AIS incorrectly, and correlate those with the large number of stupid people you assume are using it.

As for that last sentence of Dave's - that is how I have described our usage of COG vectors throughout this thread, although I am willing to believe that perhaps my writing is not clear.

Mark

[goboatingnow]

BY THE WAY, Ive seen some significant class class A errors, like ROT that simply make no sense, ( leaving aside the user data thats often way wrong).

dave

[colemj]

I have one "gotcha" that isn't necessarily apparent (until you think about it) when using AIS: the CPA is based on the position of the GPS receiver on the ship. Even without the error associated with GPS, the actual CPA of the part of the ship you are concerned about could be off by up to 400 meters (~0.25nm).

Mark

[colemj]

Originally Posted by goboatingnow

BY THE WAY, Ive seen some significant class class A errors, like ROT that simply make no sense, ( leaving aside the user data thats often way wrong).

dave

We have seen position and speed errors that didn't make any sense. Once we had a ship jumping all around our screen by dozens of miles and in and out of our range. Its AIS would go off for a while, come back on, go off, etc. I assumed they were having problems with the system and were trying to reboot it.

It was strange though.

Mark

[Dockhead]

Originally Posted by colemj

Come on DH - you keep telling me you don't say things like this, but you keep saying them! Can we agree to stop assuming everyone but ourselves are stupid? And agree that there is no general problem using any technology? And agree that there will always be a few stupid people whether they are using a technology or not?

If so, then these discussions will be more fruitful. If not, then please point to all of the boats being run down from using AIS incorrectly, and correlate those with the large number of stupid people you assume are using it.

As for that last sentence of Dave's - that is how I have described our usage of COG vectors throughout this thread, although I am willing to believe that perhaps my writing is not clear.

Mark

I am certainly not saying that "everyone but ourselves are stupid", and once again, this is not a technophobic discussion. You again misapprehend my point.

I was the first to admit that I take GPS position as infallible, and let me also be the first to admit that when I read the CPA off the AIS display, I don't naturally perceive the "cone of error" inherent in the reading. Any more than I naturally perceive the difference in error at different zoom levels on an electronic chart. It is not at all a matter of anyone being stupid. It's a matter of the nature of the way the information is presented. It's a call to think about and figure out how to interpret the information in a way which makes it useful. All of us have to think about it, and I am the first one to admit that I have to overcome the natural way that we all interpret this data. I am trying to help myself as much as anyone else by bringing these things up.

I think you yourself, in one of the early posts on this thread, said something like "A mile! If you see a couple of cables on the display, then what's the problem? You're overthinking this; how could you ever get across the Channel, etc." [Pardon me if I'm misquoting or mis-paraphrasing.] In open water dealing with high speed ships, this is all wrong -- as I guess you see by now after all this discussion and examples. But the fact that you would think that way by no means means that you are stupid -- which you are obviously not. Or inexperienced. It's a natural way to interpret what AIS tells you. It is precisely the mistake the Nedlloyd master made in the Wahkuna disaster, and that guy was surely not stupid or inexperienced. That's why it's SO worthwhile to talk about these things and to talk about the inherent dangers in using this kind of data the way our instruments present them, and force yourself to think about the cone of error and sources of it. It does not mean that we are knocking the technology or calling anyone stupid.