[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
http://layers.openstreetmap.fr/?zoom=5&lat=39.9597&lon=-78.77311&layers=0B000FFFFFFFFFFFTFFFFFFFFFF

Regarding Native American reservations, while there "is no consensus" there
are a couple alternatives to admin_level (using boundary=* instead)
mentioned here:
http://wiki.openstreetmap.org/wiki/United_States_admin_level#Native_American_reservations

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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