Had two unusual things on AIS
the past few days. The first was on the trip from Capri
to Napoli. LOTS of passenger ferries on this route
, and I was watching one northbound and one southbound that were passing a few miles east of me. They passed within half a mile of one another, and when the targets separated the northbound ferry
appeared to be moving sideways. I checked details on the AIS
and his heading was 105, but course was 010. The display on the chart plotter showed him moving sideways at almost 30 knots!
The second was a little harder for me to explain. We were north of Napoli and my wife had the helm
while I napped. When I woke up, she told me that a 78 foot fishing
vessel was on AIS about a quarter of a mile off the port beam but she couldn't find it. We looked, but there was nothing there. The course, SOG, etc. all showed this to be a vessel underway, but we couldn't see it. I turned on the radar
and found what I think was the vessel, about three miles off to starboard. I watched it for a while and it appeared to track the course and speed of the phony AIS target, so I believe that was it.
This second one is puzzling to me. How can one's AIS transmitted data show a position so far off of actual?