AIS VHF and Chaos Theory

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rhinorhino

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Let us suppose that by law all cars are required to be fitted with a mobile phone and that they are all also required to have the mobile number painted on the sides.
The advantage? That on friday rush evening rush hour we can all call each other up, and stop worrying about the Road Traffic Act and the highway code and invent our own system. The likely result is clear. Chaos!
Yet AIS is being touted as a great thing for just this reason.
How often does it have to be said, VHF is not a collision avoidence tool.


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I don't think anybody is saying that VHF is a collision avoidance tool. However, there are good arguments to suggest that AIS and VHF/DSC will help you make a decision and take some action to avoid a collision.

Therefore it has to be a good thing - or at least better than nothing at all.

<hr width=100% size=1>I'm average size, Its just that everybody else is short.
 
The main reason why VHF is discouraged as a collision avoidance tool is because of the likelyhood of making contact with the wrong vessel. This wastes precious time and can further confuse the situation.

AIS mitigates against this, and it may well be that in time the advice will change and DSC VHF in conjunction with AIS becomes a genuinely useful CA tool.

<Yet AIS is being touted as a great thing for just this reason> Where on earth do you get the idea that AIS is there so that we can invent our own system?

Look at the airline industry. They have their equivalent of AIS, and I wouldn't describe this as being in chaos.

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I stand to be corrected, but I don't believe that aircraft speak direct to each other but rather to ground control.
Second, I was taught that the reason VHF was a bad tool for collision avoidence was three-fold; first language, second that while agreeing a course of conduct with one vessel you may conflict with another neither of you have seen and finally that the rules provide the solution in almost evey case without debate in any case.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by rhinorhino on 16/03/2004 18:51 (server time).</FONT></P>
 
Definitions of VHF

VHF has a primary role to play in AIS, and possibly but not neccessarily, a secondary one.

Primarily, a discrete VHF radio in the AIS kit sends out bursts of information that are received by other discrete boxes on bridges and shore stations and are converted to be displayed as data on AIS screens, possibly but not neccesarily linked to a chart plotter or radar display. No voice comms at all. And it could equally well be done by microwave or infrared, semaphore or whatever, if someone could make it work.

Secondarily, and at the discretion of the vessels involved, using a normal DSC-enabled voice VHF would allow vessel A to query the intentions of, or pass information on its own evolutions to, vessel B. Vessel A knows the MMSI and call sign of Vessel B. It's not neccessary to do this, and if both vessels were behaving as required under colregs there would be no need for contact. But just occasionally it might avoid loss of the no claims bonus.

<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>
 
Automatic collision avoidance, pah!

Guys,
We can't be serious about this! What is wrong with the adage of "If I'm not sure, aim at the bum of the vessel that would run us down".

Regarding aircraft and AIS, you might all be aware of the awful collision over Switzerland that resulted the deaths of a party of school children and a cargo plane crew. Both aircraft were fitted with, and used the AIS that told them how to avoid each other but were overrriden by ground control.

IMO, the direct result of ceding control to a system, rather than prudent navigation is a rise in collisions that could have been averted by the use of good old commensense.

Use this system as an aid, but anything more is abdicating responsibility for a skipper's due diligence.

I have worked with IT and safety-based systems all of my working life and wouldn't trust most of them with yours, let alone mine.

Rant over, back to communting home to the South Coast.

Chris

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Ok, I\'m going to have a rant

My first channel crossing was on a 40ft Buchanan sloop. Her engine didn't work, and she was prone to leakage. She never did have a VHF, and I don't ever recall knowing where the flares were kept. Her echo-sounder was knackered, but we had a hand lead. The harnesses were mouldy and spliced on at the harness end with a crude hook t'other end.

Apart from our own navigation estimates, we could easily check our positions using RDF. The log had more knots than Houdini and more weed than Bob Marley, so was rarely consulted.

This continued for a number of years, and we visited Spain and Portugal on our optimistic travels. Eventually the owner came into some dosh and fitted an engine. I purchased a sextant, which I keep handy to this day, an our landfalls improved.

Warp forward, here we are today.

I wouldn't now dream of taking these risks, and many crossings later I can and do still learn. But if it all went pear shaped, I hope I could still get to Cherbourg in time for a decent meal and a bottle of wine.

So, onto the rant. Why does a purely technical report lead to such outbursts? Are you imagining that I'm saying you must have one? Rant over, go for the bum.

Tome

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The DSC-enabled voice VHF aspect of AIS has been over emphasized by technically inept journalists who cannot picture how the key aspects of AIS will tick.

AIS will allow the small boat skipper to immediately picture what the big boys are doing and get out of the way without recourse to a voice VHF conversation. This picture of ship movement will be presented with zero operator input allowing you to focus on in-cockpit eyeball helming during stressful encounters.



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