I'm really confused with that Google Maps screen - in my area it is showing some of the local shipping with their AIS transponders - but not ALL of them, as in my own, for example, is missing from the map, but clearly visible on every ship finder AIS I've used before. How do these ships get incorporated into APRS - because they certainly have no ham radios on board. I've clicked on one of the boats, and I'm listed as being 250m from it - but I'm invisible. The local repeater is there, and also a diving boat in the middle of the houses!