AIS in the Solent

[Twister_Ken]

There is a finite limit to the number of timeslots, so there will come a point where the number of transmitters needs to be limited.
Or more channels will be needed, like with mobile phones.

TBH, the course of many ships in the Solent is hard to predict in detail more than a very few minutes ahead.
The big 'uns out of Fawley are easy, but the medium sized stuff needs thought sometimes.

But sailing in the Solent always requires knowing where you are relative to the channels and knowing what the tide is doing.

I can only think of one time when AIS would have been significantly useful, and that was thick fog.
Rest of the time it is a toy, or at worst a waste of time that would better be spent looking around.

Cross channel is different, for that I really like AIS.

That's a big ditto from me.

 

[prv]

There is a finite limit to the number of timeslots, so there will come a point where the number of transmitters needs to be limited.

As I understand it, the protocol is designed to cope with timeslot exhaustion. So you still don't need the blunt instrument of turning off transmitters, they will simply not transmit if they can't get a timeslot. I believe Class A have a clever scheme for cooperating for an equal share of the slots, so they will all get a turn but might have to update a little less frequently if the band is absolutely packed with other Class A. Class B only ever grabs the slots left over by Class A, so yachts will never obscure tankers, but there isn't the cooperative mechanism between Class B transmitters, it's a bit more chaotic. So if the leftover slots for Class B get full then some of the targets might become a bit intermittent - but since we all agree that nobody's interested in Class B vessels on a sunny day, that shouldn't matter anyway.

Pete

 

[DJE]

As I understand it, the protocol is designed to cope with timeslot exhaustion. So you still don't need the blunt instrument of turning off transmitters, they will simply not transmit if they can't get a timeslot. I believe Class A have a clever scheme for cooperating for an equal share of the slots, so they will all get a turn but might have to update a little less frequently if the band is absolutely packed with other Class A. Class B only ever grabs the slots left over by Class A, so yachts will never obscure tankers, but there isn't the cooperative mechanism between Class B transmitters, it's a bit more chaotic. So if the leftover slots for Class B get full then some of the targets might become a bit intermittent - but since we all agree that nobody's interested in Class B vessels on a sunny day, that shouldn't matter anyway.

Pete

So does that mean that if the powers that be ever want to make it compulsory for yachts they are going to have to find a lot more bandwidth from somewhere?

 

[Martin_J]

It is compulsory for all boats in some areas... take the waters around Singapore for example.

As to time slots.. with about 4500 available in each minute.. and once a clear time slot has been used by a vessel it uses same slot each time.. and with the globe split into small time slot zones.. it'll take a lot of transmitters to overload it..

Nice description of the time slot usage here...
http://www.navcen.uscg.gov/?pageName=AISworks

 

[Birdseye]

Foggy, was it?

Maybe but after doing the compulsory two radio checks on 16, what else is there to play with whilst motoring down the solent? No point in having lots of electronic toys and not using them is there?

 

[prv]

Maybe but after doing the compulsory two radio checks on 16, what else is there to play with whilst motoring down the solent? No point in having lots of electronic toys and not using them is there?

I have the second control unit for the stereo installed right next to the AIS display, so I guess I could play with that

(In all seriousness, as I mentioned upthread, unless I'm intending to cross the Channel I generally leave the cover on the AIS.)

Pete

 

[Cloona]

What is AIS ?