AIS Target display time

[geoffr]

I'm wondering how a chartplotter deals with an AIS target which stops transmitting - how much longer after the last transmission does it keep it shown on the screen?

Is this configurable ? (Raymarine, Garmin, OpenCPN)?
Different for class A and B?

thanks.

[toddster8]

You are going to have to read the manual on this. There should be a way to read the time that the last signal was received. For one thing, Class B transmits only once every six minutes, so you should not assume that anything you see on the screen is "real time."

[AedanC]

It can be configured in OpenCpn all right, but not separately for class A and B. I don't know about the others.

[StuM]

Originally Posted by toddster8

You are going to have to read the manual on this. There should be a way to read the time that the last signal was received. For one thing, Class B transmits only once every six minutes, so you should not assume that anything you see on the screen is "real time."

That's a huge over-simplification and misleading.

Class B transmissions may be received up to 6 minutes apart, but frequently are transmitted every 30 seconds (depending on type of data,SOG and number of receivers in receiving equipment).

[smac999]

often you get a triangle with a line through it after it stops transmitting. then it'll disapear

[MarkJ]

Settable in the plotter.

OpenCpn has a default of 8 minutes. You then see the target with a black line through it.

At Sea I have it set to longer.


Mark

[geoffr]

Mark,

Thanks - that is exactly what I'm looking for.. now just need the default for Garmin/Ray plotters

[wrwakefield]

Geoff,

It is configurable, with alarms, on the 3 main primary systems we use: OpenCPN, B&G Zeus Touch Chartplotter, Vesper Watchmate 850 AIS transceiver.

I don't remember the configurations allowing for differentiating between class A and B AIS transmitters, but would have to double-check to confirm.

Cheers! Bill

[tanglewood]

It looks like for an IMO compliant display, the lost target icon displays when there has been no report for the shorter of 6 minutes or 5 intervals. Both Class A and B devices report position every 3 minutes when stationary which is the longest interval. The 6 minute report interval, BTW, is for static data like Ship's name, and is the same for Class A and Class B.

I don't know whether consumer devices follow the same rules, but I can't see why they wouldn't.

Again, on an IMO compliant device, lost targets only go away when explicitly dismissed. I find in practice that they just disappear from the screen and are out of sight, out of mind.