What is on the river

Methodology

AIS transmissions heard over Greater London, via AISStream. Unlike every other feed here this one is a broadcast rather than a request: vessels transmit when they choose to, so there is no endpoint that answers what is on the river now — the server has to have been listening. It holds one socket open and accumulates what it hears, forgetting a vessel after twenty minutes of silence. Carrying AIS is mandatory for larger commercial craft and optional for small ones, so this is what the river is broadcasting rather than a census of what is on it. The count climbs for the first several minutes after a deploy while the table fills.