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Old 03 September 2011, 11:53   #11
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For those that dont know what the 'Costa Del Solent' can be like here are a couple shots of one of our monitors taken today around lunchtime.

Bear in mind this was just a typical 'end of the season' type weekend with no special race events on.

Probably should'nt mention this but VTS have little choice but to filter out class B transponders......it would be near impossible to safely guide commercial traffic otherwise.

Simon
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Old 03 September 2011, 13:12   #12
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Simon, these images as you say are quite quiet but it was a usual day out on the area today. Hamble looks busy as ever and all sunsails show up now with their fleets.
You can get a similar image from the I phone app also.

(Pm sent re tickets)
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Old 03 September 2011, 13:47   #13
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Quote:
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here are a couple shots of one of our monitors taken today around lunchtime.
I personally don't find that 'too cluttered'. There's clarity in the direction of each vessel and therefore which ones might become a threat. If you are doing close quarter manouevres in a busy area then surely by zooming in you will 'space out' the targets. Interestingly, the heading line on all markers is the same length. On my Garmin it's length varies depending upon the speed of the vessel which helps you determine which are approaching fastest.

If you set a filter, does that also affect automatic collision warnings or do they still sound the alarm.
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Old 03 September 2011, 17:09   #14
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I personally don't find that 'too cluttered'. There's clarity in the direction of each vessel and therefore which ones might become a threat. If you are doing close quarter manouevres in a busy area then surely by zooming in you will 'space out' the targets. Interestingly, the heading line on all markers is the same length. On my Garmin it's length varies depending upon the speed of the vessel which helps you determine which are approaching fastest.

If you set a filter, does that also affect automatic collision warnings or do they still sound the alarm.
'Evening Erin...

Yes, your quite right, it was'nt too cluttered today but as C2Ribs also says, today was just an ordinary day.
During busy weekends when the sun is shining and a good breeze is blowing the number of targets shown can easily tripple.
Cowes week and the ''around the island race' are a complete nightmare.

Imagine your a pilot trying to bring in to port a large container vessel or tanker, VTS tells you that an outbound cruise ship is nearing the 'clear channel vessel' area meaning that only one vessel can be in the area at any time (hatched area on the chart around the west Brambles bouy, the cruise ship is south bound and your north boaund) . Now your too far away to visually sight the cruise ship so you check the plotter to see where she is. Imediately you realise that her name is already partly obscured by a yacht sailing close by and secondly, when you pan back out, the target practically disapears under a splattering of class B targets.
As pilot, your now having to rely on radio communication with both VTS and the southbound cruise ship to determine where she is rendering the AIS system (which should be a valuable tool) useless. This also creates distractions for both you as pilot of the container ship and also the pilot of the cruise ship who could very well be having the same problem.

VTS filter out clas B stuff for similar reasons, they have to track all commercial traffic entering or leaving the port. They keep an eye out and (believe me when i say this) they are very quick to call up any wayward vessels that should stray outside of any channel or be on a collsion couse with another ship or fixed object.

Yes, all our vessels can set the track to vary dependant on speed of the target but here in the ofice we dont normally bother.

The real question once again has to be " did all those leisure vessels on the screen shot really need to be transmitting? "..... Most of the targets on the screenshot were yachts, so do we really believe that those yachties were paying attention to their chart plotters (the ones that actually have a plotter screen by the helm and not down below near the chart table).
Ask any Master or Pilot of any commercial vessel what his primary means of collision avoidance is and they will probably tell you their eyes...actually looking out the window and seeing what is happening rather than relying on electronic tools.
Now, as i have previously mentioned, when it becomes difficult to actually 'see' ie: night time, fog or other poor visibilty conditions or when your in a situation where commercial traffic would not expect to cross paths with a leisure vessel ie: crossing a TSS or other busy offshore channel, then yes, use the AIS but otherwise keep it switched off.

A short term solution to the problem would be to have commercial targets appear in a diferent colour than leisure targets, not perfect but a good start.

Ian, yes, the Iphone app (ship finder) is very good, many of us use it when were not around a chat plotter.

Simon
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Old 03 September 2011, 17:29   #15
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another problem with Class B, many dont have basic details included, then I am able to rule out vessels which are not a risk to me!!!!
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Old 03 September 2011, 17:38   #16
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Its possibly unfair to "blame the yachties" for leaving it turned on. Cetainly before you posted I would never have considered turning it off if I had it - it strikes me as something that you could forget to turn on in the dark/fog etc and so best left on all the time; indeed many systems will be hard wired in and not simple to turn on or off. As I understand "standard" systems then turning off would essentially turn off the "receive" mode too - which seems dumb, although I take your point that looking out the window is better, but familiarity with the systems in daylight makes them easier to use in poor vis/night. And given your comments elsewhere about leisure sailors apparent incomprehension of the world around them I'd have thought an electronic aid with an alarm of they are on a collision course would be a good idea. Should also make it easier to identify them to scream at them to get out the way or for VTS/HM etc to follow up on dangerous behaviour - so in that sense should benefit commercial traffic in busy areas.

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A short term solution to the problem would be to have commercial targets appear in a diferent colour than leisure targets, not perfect but a good start.
I think therein lies the problem. The "designers" of AIS perceived the problem hence why the split into 2 categories, and hence why large vessels (cat A) get priority and more frequent, higher power broadcasts etc. They were aware it could "clutter" the airwaves, and presumably also the ability of those receiving the information was also considered. It strikes me that part of the problem is how "you" are displaying the information. Firstly as you say all the vessels show as the same colour. You've probably seem systems which differential colour based on vessel type. Secondly you have all the vessel names showing constantly. With so much information you have overload, again I'd have thought hiding that info, at least for class B transmissions, was logical (the detail can then be displayed by hovering over or clicking the specific target if necessary). Similarly it would be easy enough (for the software developer) to make class B or certain types of vessel appear as smaller icons which would give less screen clutter.

I don't know to what extent the problem is in the design/development of the software/firmware and to what extent it is in the setup/use - but the "online" software already demonstrates that several of these features are possible.
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Old 04 September 2011, 03:15   #17
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Good morning Polwart....

Yes, the points you have made are valid and forgive me it seemed like I was pointing the finger only at yachts.... Truth is more and more motor vessels are being equipped also... Still a minority but they are gaining ground.

It probably will seem strange to most people that our commercial AIS sets do not differentiate between leisure and commercial since, as you quite rightly say, many people are familiar with the iPhone app or online AIS tracking software. Each vessel updates their software in a monthly basis (with chart corrections ) so if a modification is available we would of received it by now.
Perhaps other manufactures offer such a system?

A very important point to remember, and it's a point that I should of made earlier on in this thread is that contrary to commercial shipping,there is no requirement for leisure vessels to install and use AIS....
Unfortunately this means that bridge crews of commercial vessels regard class B transponders as a hindrance rather than as a benefit. They are more than aware that some yachts transmit, and some don't.
I suppose you could almost relate it to 'Tracer' ammunition when being fired from a gun... You see the tracer rounds shooting up into the sky but for every tracer round you see, another 3 or 4 bullets have left the gun.

Returning to the OP and the fact that class B signals were potentially being filtered out....I Would have to confess that for all my previously given reasons I would be in favour of the ability to filter out class B signals.

Very interesting debate though...

Simon
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Old 04 September 2011, 03:18   #18
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I have a Raymarine AIS650 transceiver AIS650 and it has two different ways of "going silent", either by wiring in a switch or by using the multi functional display, there is no switch for turning it off other than cutting the power.
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Old 04 September 2011, 08:05   #19
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A very interesting insight Simon, thanks. I suppose I view the AIS thing slightly diferently in our waters where we don't have anything like the concentrations of traffic that you get and therefore I feel that AIS is a good safety measure particularly in fog and when we have high speed ferries operating nearby. I am seriously considering fitting a transponder to my boat for those few occasions where I might want to make sure I have every chance of being seen. Perhaps I'll also turn it off in all other 'safe' situations.

Like Cookee's Raymarine, the Garmin has a 'silent' mode via a dedicated switch although this is optional on any installation. The idea of different coloured triangles for class B and A vessels is a good idea. Perhaps a good alternative software option would be a temporary filter button that only removes class B transmissions for 30 seconds or so, so that you can identify the >300 tons vessels.
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Old 04 September 2011, 09:28   #20
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Perhaps a good alternative software option would be a temporary filter button that only removes class B transmissions for 30 seconds or so, so that you can identify the >300 tons vessels.

...hmmmmm, interesting..............now what was the telephone number for the patent office?



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