Buoys are not boats any more
A feeder who runs a new AIS station in Santos flew down the channel into the port and found a row of identical little boats sitting dead still in the water, each labelled "MMSI 9971019xx · Vessel · 0.0 kn". They were buoys. Their screenshot from OpenCPN showed the same MMSI as BOIA 5, a starboard-hand mark, and AIS-catcher drew the whole channel as a line of yellow diamonds. Thanks for the report, it was a good catch.
What was going on
An AIS receiver hears more than ships. Buoys and beacons can broadcast their own position (message type 21), and a shore station can broadcast a virtual mark at a spot where nothing floats at all. These transmitters use MMSI numbers starting with 99. Base stations, search-and-rescue aircraft and distress beacons share the same radio channel too.
Our upstream feed only ever asked for ship messages, so none of this used to reach us. Our own receivers forward everything they decode, and the server put every one of those transmitters into the ship list. So a buoy got the default hull, a "Vessel" plate, and you could lock onto it and add it to your collection. It also counted as a vessel on the station page and in the coverage numbers.
What changed
- Aids to navigation are their own thing. In the sim a real mark is a small floating buoy, coloured by its type: red or green for lateral marks (we follow the IALA region from the country code, so Brazil and the rest of the Americas get region B colours), yellow for cardinal and special marks, black for isolated danger. A virtual mark is a translucent diamond hovering over the water, since there is nothing physical to draw. Fly within about 1.5 km and a small plate shows the name and the mark type.
- On every map (the big in-game map, the minimap and the public
/map) they are chart-style diamonds under the ships. Virtual marks are hollow. - They are not vessels. You can't spot them, they don't count in "vessels heard", and they stay out of fleet search. A buoy your antenna hears still counts toward your station's coverage map, because hearing it is real reception.
- Base stations, search-and-rescue aircraft and distress beacons are dropped from the ship layer. A base station has no hull, an SAR plane is not on the water, and a man-overboard or EPIRB beacon is a person in trouble whose position has no place on a public map.
- Feeders sending raw NMEA over UDP now get their buoys decoded as well; before this they were silently ignored.
A handful of buoys already ended up in people's collections. They stay where they are for now. If you have one, it's a souvenir of the bug.
Have a receiver near the water? The ships network shows how to connect it.