[Tagging] admin_level on nodes: wiki vs practice

Fernando Trebien fernando.trebien at gmail.com
Wed May 14 02:51:35 UTC 2014

Applications could avoid that mess if they supported and preferred the
"admin_centre" role of relations. For a long time I believed that the
only practical reason for placing "capital=yes" or "state_capital=yes"
on a node was to help the renderer decide how to render the label; the
renderer could then avoid the trouble of handling relations, even
though it's not thaaaat hard to handle them, and a good renderer would
have to handle them to support multipolygons anyway. Routing and
geocoding apps are required to support boundary relations in order to
work properly in many other situations, so they should definitely
support the admin_centre role, and also give precedence to it in order
to handle contradictions between the node and the relation (not only
admin_level, but also name and other tags).

On Tue, May 13, 2014 at 11:29 PM, Andreas Goss <andig88 at t-online.de> wrote:
>> Please explain why admin_level on place nodes harms the database, or
>> refrain from removing it. Thanks.
> I actually put it back in Berlin after I took a 2nd closer look at Germany.
> Which then actually revealed that all our state capitals are tagged with
> admin_level=6 when they should be 4 as far as i understand if you tag them
> at all...
> Which then actually made me rethink and discover a possible problem when
> tagging the node.
> If you tag Berlin admin_level=2 do you assume it also holds admin_level=4?
> 6? (Then you realize that with Berlin you actually have a special situation,
> because it is a city state. But that wasn't even what I was going for.)
> Now let's say things in Germany would have went a bit different 20 years
> ago...
> (http://en.wikipedia.org/wiki/Decision_on_the_Capital_of_Germany).
> Bonn would have become the capital of Germany not Berlin. Now I tag Bonn
> with admin_level=2. The problem is that Bonn is located in North
> Rhine-Westphalia whose capital is Düsseldorf. So how do I now know that Bonn
> isn't the capital of NRW? Do I have to tag other capitals with
> admin_level=2,4 in order to show that they are country and state capitals
> and admin_level=2 only stands for country capital? Am I going to have to tag
> nodes with admin_level=2,4,5,6,8... in order to be able to tag e.g. Bonn as
> admin_level=2,5,6,8...? (Germany has no lvl 3) Because there is no "exclude"
> option.
> Andi
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Fernando Trebien
+55 (51) 9962-5409

"Nullius in verba."

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