AIS is one of my favorite subjects. So much so, that I installed an AIS broadcasting station in my marina in Portsmouth, NH, a few weeks ago. It had irked me for a long time, that there had been an AIS hole between Boston and Portland, i.e. no online AIS viewing coverage at all.
My station can now be seen on Ship Finder (Apple App) and Marine Traffic dot com.
Recently, I got my hands on a used Class A unit. These are the commercial equivalent of the Class B units, typically found on recreational vessels. While Class B must be preprogrammed by the dealer, the Class A units can be programmed by the owner.
This is also one reason for why you do sometimes see AIS targets which do not make much sense, simply because the skipper did not bother to update all information.
I got a kick out of reading the vessel classification table for AIS in my owner's manual. It seems like, officially, there are only 6 categories for recreational vessels.
Guess how many there are for commercial vessels & ships of war? .... Well? ... 91 repeat 91.
DUN stands for ketch. You would not want to run into a CIM. It could hurt you because this is a cement carrier. What you do not see, cannot hurt you, maybe? SMN is the official classification for submarines.
Well, and XXX, what is that? A floating bordello? Maybe, this goes together with ESC?
XXX is an unspecified vessel and ESC is an escort ship.
Fun stuff, indeed.