We're cruising down the Chesapeake right now (50* and calm winds, perfect trawler weather). It seems that the class A commercial vessels show up on marinetraffic.com, but we class B types show up only sporadically. I thought I read someplace that the class B signals are captured by local receiving antennas and the AIS data is sent to marinetraffic.com. If so, that would explain a lot.

Can anyone shed any light on this so I don't have to spend half the day googling it myself?