Hi Jim, I can see your questions were directed to Hans, not me. But since the forum at large was cc’d, and since I’ve already weighed in on the ‘AIS-on’ side, I’ll add my $.02 FWIW. In your scenario with numerous targets and good vis, some of which are transmitting AIS, you can evaluate instantly whether any of those targets is a threat by virtue of your user-defined settings on your plotter. In our case, an AIS target with an unacceptable (defined by us) CPA will be flashing red. Regardless of any non-AIS targets around you, you know you have an issue with this one target right out of the chute, so you can evaluate the other targets already knowing you will have to take steps (assuming you’re the give-way vessel) to avoid that one target. This saves time and rules out the other AIS-transmitting targets as threats, thereby lessening the overall pucker factor of the situation. If I am looking out the window at 11 targets, my speed and accuracy at identifying the potential problem target(s) will be better, every time, if I have AIS returns from at least some of them. And I don’t care if they’re pleasure or commercial craft. It can only help and there is no down side to having the data. Assuming your radar is running, you certainly CAN discriminate between the AIS-transmitting and non-transmitting targets, because (again assuming you have onboard NMEA technology readily available for many years) the AIS-transmitting targets are so identified on your radar, whereas the non-AIS ones just look like regular targets… which you can then individually interrogate via ARPing them or whatever. As far as one other boat in clear conditions, you are right. With one boat to focus on AIS is not going to impact your risk. I will concede that, though I’m as proficient as anyone at identifying a collision course while watching over a few minutes, my visual estimation of both time and distance is embarrassingly poor. This might be why I got comfortable so much more quickly with AIS and ARPA technology compared to my husband. But both he and I agree on the trend when it comes to AIS on vessels of all types and sizes. Which was really my point: not that you *need* AIS or for other pleasure craft to be transmitting AIS signals or not. But that it might behoove you to get comfy with it, so that it’s a help and not a distraction when it becomes more prevalent and, ultimately IMO, required in the U.S. Cheers! Valerie m/v Buffalo Nickel Phuket, Thailand > > At different times on the Pungo, I noted a cluster of boats: 3 radar returns (confirmed visually), two AIS hits; 7 radar returns (confirmed visually), 4 AIS hits; 11 radar returns (confirmed visually); 5 AIS hits. I see no advantage to the AIS hits IN THOSE CONDITIONS, since you can't discriminate between the boats with AIS and the boats without AIS. And besides, even boaters with no experience at all should be able to avoid hitting another boat in clear, unrestricted visibility. So, please educate me on the value of AIS in those circumstances. > > So how, specifically, did AIS transponders from a sunset of other boats increase your sense of - or your actual - navigation safety over simply looking out the window? I DON'T GET IT. I'm just not smart enough - I just don't have the insights - to "get it" without help. > > Jim