[Tagging] Places & admin boundaries

Pierre-Alain Dorange pdorange at mac.com
Sun Oct 28 20:14:54 GMT 2012

"Petr Morávek [Xificurk]" <petr at pada.cz> wrote:

> 2) Boundary relation or place=* for higher administrative units?
> The overlap is especially visible in case of countries (but same
> arguments apply for other units like states, counties, ...).
> Majority of counties are in database represented twice - as node with
> place=country and with admin_level=1 boundary relation.
> This is again one real object represented by two completely distinct
> objects in the database. Even though the common wisdom is that country
> polygons are marked with admin_level=2 relations, most of the don't have
> place=country tag. This is somewhat confusing - if I want to specify
> currency, population etc. of the country, where should I put it? Node,
> boundary relation, both?

Here in France the have tagged about avery admin level with relation.
Each relation contains the bordary description (way) and an admin_centre
associated a a node representing the admin_centre, for the country the
node was placed on the "Palais de l'élysée" were our president is (and
the main power in our country).

For region or state, the same rule apply. And also for city (the
admin_centre) is put (and here there was 2 variations) : on the city
hall or on the "main place representing the best the center of the city"
(difficult to define, but often easy to put on the map for people from
the city).

We used a lot the relation and it works very fine for us.
We don't see this as a twice representation but more as a complementary.
The boundary define the geographical limit and the admin_centre define
the "political center" of the admin.

We put all data related to the admin in the relation, but for historical
reason sometime there was other (old, previous to relation) value on the
node (admin_centre).
The usual meaning for population on a node is applying just for the node
(the city for example). 
On the opposite a population in the relation define the whole population
inside the adlin boundary (including the city).

Here in France, some city limit can include 2 or more other small city
that was one day autonomous but was admin connected to the main city.
In this case, each old city was tagged "hamlet" and can have also a
population tag, but only related to the hamlet...
I dont't think my explanation was clear on this point... sorry english
is not my main language.
Pierre-Alain Dorange
OSM experiences : <http://www.leretourdelautruche.com/map/>

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