The vessel source accepts an optional area and sends it as lat, lon and
radius_km. The vessel layer asks for the area the camera shows (centered
on the middle of the screen, sized by camera height), or every vessel
from high enough up, and asks again when the view moves or zooms by a
quarter of that radius. vessels_in_area names its area too. Servers that
hold every vessel may ignore the area; callers still keep only what is
inside it.
Vessel tools read the source's default of the newest 12,000 vessels while
the server keeps up to 50,000, so a lookup could miss a vessel still held.
They now ask for more than any server keeps and receive everything it has.
Add vessels_in_area, find_vessel and get_vessel_track over the live
vessel source, and a ships section in situation_brief. Without an AIS
key the source's own message reaches clients as an unavailable feed.
Sameh Khamis