Last week we pulled into the lee of an island to anchor. On the port beam, 0.2 miles away on the radar was target, which was an vessel at anchor showing the proper lights. There was also an AIS-generated triangular target only .05 miles away are the port beam. But there was no moon to see anything and there were no lights from the vessel. Problem was it was the AIS transponder signal from the boat on are starboard beam!
I sure would not have want to rely on an AIS-generated CPA based on a position that was 1/4 mile off the actual position of the vessel!
Anybody else run into this situation before?