[Talk-us] Differences with USA admin_level tagging

Brad Neuhauser brad.neuhauser at gmail.com
Tue Jul 11 19:45:04 UTC 2017

Frederik's description of colored polygons made me think of the French OSM
instance, which can display admin level, ie

Regarding Native American reservations, while there "is no consensus" there
are a couple alternatives to admin_level (using boundary=* instead)
mentioned here:

On Tue, Jul 11, 2017 at 2:03 PM, Frederik Ramm <frederik at remote.org> wrote:

> Hi,
> On 07/11/2017 08:18 PM, OSM Volunteer stevea wrote:
> > I'm glad Adam brings up the topic of Gores, as I'm also unclear on how
> such "holes" get "punched into" larger (multi)polygons via tagging.  For
> example, I am "sort-of-sure" (but not positive) that in Vermont, a "gore"
> (or grant, location, purchase, surplus, strip...usually the result of
> "leftovers" from survey errors) get a tag of admin_level=4 to accurately
> reflect that the governmental administration happens via state-level
> bureaucracy.
> I think there might be a misunderstanding here and I would like to chip
> in before this gets out of hand, even if I don't have any specialist USA
> knowledge:
> If you have an admin_level 4 entity - like a state - then the boundaries
> with admin_level 4 are the outer demarcation of that, i.e. they separate
> the area where the state is responsible from the area where the state is
> not responsible.
> The only reason to have an admin level 4 boundary inside a state, would
> be if there was somehow a piece of *federal* territory inside the state.
> Only then would the state have a "hole" in it that would be tagged with
> admin level 4! An area inside the state that is state-governed because
> of a lack of admin_level 5+ entity does not need its own boundary. It is
> defined by the boundaries of the admin_level 5+ entities that surround it.
> > without using a multipolygon relation,
> You will be using boundary relations which are practically identical to
> multipolygon relations. Any attempt to create a "lower 48 states"
> polygon without relations would hit the 2000 node limit.
> > is it correct within OSM to tag, say a very large "lower 48 states"
> polygon with admin_level=2 AND ALSO tag admin_level=2 on, say, a
> national_park inside of it
> That would only be correct if the national park was *not* part of the
> lower 48 states but somehow part of another nation.
> I'm not 100% sure what you want to achieve but think of it like coloured
> polygons. If you have an admin_level 2 area for the USA, think of that
> as one colour, and then you have a lot of states, each with a different
> colour. In those areas where the "USA colour" shines through, because
> they're not covered by any state, that's automatically federal territory
> and you do *not* want an admin_level 2 boundary surrounding that
> (because then not even the "USA colour" would shine through, there would
> be nothing there).
> > Guidance by knowledgable people with real answers might guide us on a
> number of these situations, not just "Gores" (et al) but other kinds of
> "hole" tagging without multipolygons.
> If you mean not only "without multipolygons" but "without boundary
> relations" too then I think you should stop right here and leave it to
> people who can work with relations.
> Bye
> Frederik
> --
> Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"
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