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 ..

View attachment 188317View attachment 188318

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 If you look at the plotter and it says "TCPA: 1 minute" that information could be 30 seconds out of date.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

 

[st599]

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 ?
View attachment 188345

2000 timeslots per channel, 2 channels, each big ship transmitting every 2 secs. At least 8000. But whether your receiver has enough storage is a different question

 

[lustyd]

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

If it's busy enough to matter you shouldn't be anywhere near the AIS display, so it makes no real difference which version you have.