"Darn, I was just in Winyah Bay last week, but I hadn't found out yet that the PO had turned off the AIS input to the chartplotters."
Even if your AIS input to the the chartplotter
was active you might not have seen the AtoN targets. My 15 year old Raymarine
C120 does not recognize the AtoN target type and does not display the targets nor show them in the target list. It looks like the AtoN target type was added after the last software
update to the C120 around 2009. Also the target icons are difficult to see in OpenCPN
(although they are in the AIS list) because they are plotted on top of the existing chart icon.
I'm guessing the principal purpose of the AtoN targets is make the marks visible on a radar
display rather than a chart display.