Ports Nearest

Returns the N nearest ports to a given coordinate, sorted by great-circle distance ascending.

Useful as the first link in the MCP tool chain — resolve an arbitrary AIS ping / dropped pin / customer-supplied coordinate into the nearest cataloged ports, then feed any of them into /routes/find.

Distance ordering: the SQL uses simple degree-distance for selection (PostGIS-independent and cheap to scan), and the result is then re-sorted in Python by the accurate haversine distance — important near the poles and across the antimeridian, where degree-distance diverges from great-circle ordering.