AIS questions - new plotter

[westhinder]

People seem to leave their AIS transponder powered 24hrs a day in the Solent. Even when on the hard. Hamble Point & Port Hamble as an example this morning ..

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Not necessarily if you’re using MarineTraffic. That often still gives the position hours after the AIS has been switched off. I often see this when I check my track of the day on MarineTraffic at a time I’m certain my AIS is off.

 

[Lucky Duck]

‘Maverick’ is currently broadcasting its position in the owners(?) garden a couple of miles South East of Newton Creek, similar for ‘Squidward 3’ on someone’s garden in Holbury just West of the Fawley refinery

 

[Boathook]

Not necessarily if you’re using MarineTraffic. That often still gives the position hours after the AIS has been switched off. I often see this when I check my track of the day on MarineTraffic at a time I’m certain my AIS is off.

I get AIS 'positions' shown on my plotter like that. If anything it is even worse in the summer around the Solent marinas.

Edit -
Lymington as shown by marine traffic just now. How much traffic can AIS cope with before it 'packs' up as they all transmit on the same VHF channel ?

 

[requiem]

Lymington as shown by marine traffic just now. How much traffic can AIS cope with before it 'packs' up as they all transmit on the same VHF channel ?

Oh, a few thousands at least before the more distant targets start dropping.

But, there is an update rate, which is part of why it's not blessed* for collision avoidance. If you look at the plotter and it says "TCPA: 1 minute" that information could be 30 seconds out of date.


* I don't entirely agree with that, as one simply needs to be aware of potential for error and cross-check by looking up from the screen. It also reveals course changes much faster than radar.

 

[Roberto]

How much traffic can AIS cope with before it 'packs' up as they all transmit on the same VHF channel ?

For Class A or B-sotdma (often called B+) no problem, for simple B you might check here and there simple B-cstdma targets for ''Position received ... ago'' when there is a lot of traffic and draw your own conclusions