Alert areas -> FeatureCollection. The plain-JSON alert items already carry a
GeoJSON geometry (a Polygon, or a LineString for a river reach; [lon, lat]
order) — it is used verbatim. Items without a usable geometry (none, not a
GeoJSON geometry object of a known type, or a position outside ±180/±90) are
skipped.
Alert areas -> FeatureCollection. The plain-JSON alert items already carry a GeoJSON
geometry(a Polygon, or a LineString for a river reach; [lon, lat] order) — it is used verbatim. Items without a usable geometry (none, not a GeoJSON geometry object of a known type, or a position outside ±180/±90) are skipped.