Contains administrative boundaries as linestrings (no maritime boundaries yet) as linestrings.
Until z7 Natural Earth data
is used after which OSM boundaries (
boundary=administrative) are present from z8 to z14.
OSM data contains all
but for most styles it makes sense to just style
indicating the level of importance of this boundary.
admin_level corresponds to the lowest
the line participates in.
At low zoom levels the Natural Earth boundaries are mapped to the equivalent admin levels.
1 if the border is disputed.
1 if it is a maritime border.