[Tagging] admin_level on nodes: wiki vs practice

Fernando Trebien fernando.trebien at gmail.com
Wed May 14 04:04:03 UTC 2014

In Brazil, admin_level=4 is state level, so it would be
state_capital=yes. I've never really thought about it in depth because
Brazil only has 2 administrative levels with a "capital" city and the
country only has 1 capital. This is how it looks like in Brazil now:

1. Node tagged as place=city+state_capital=yes, representing a state's
capital city, placed (at least in theory) at the city's square one
point. (Replace with capital=yes only for Brasília.)
2. Relation tagged as boundary_administrative+admin_level=8+place=city
with an admin_centre role referencing the previous node.
3. Node tagged as place=state representing the state, placed at its
geometrical center. *
4. Relation tagged as
boundary=administrative+admin_level=4+place=state with a label role
referencing the previous node and an admin_centre role referencing the
first node.

I know that Germany has more than 2 administrative levels, and
probably that's why values are being used for a capital tag instead of
many tags with a single "yes" value. It does make some sense for a
renderer, but does any support more than just 2 visual styles for
capitals right now?

It would make more sense to require apps to check the relation for its
admin_level tag, then it would be impossible to have the relation and
the node contradict each other (say, by accident), and there would be
no need for a capital tag (it's always the "admin_centre" of the
country or of a state's boundary relation). This would require just a
little extra effort for renderers (which must support multipolygon
relations anyway) and geocoders, including routers (which must support
boundary relations to know to which areas each POI belongs to).

* This seems to be the practice in most countries in the world. So
much so that we could probably get rid of such nodes and just let the
rendered calculate the center and render the label there.

On Wed, May 14, 2014 at 12:05 AM, Andreas Goss <andig88 at t-online.de> wrote:
> Am 5/14/14 04:51 , schrieb Fernando Trebien:
>> 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;
> And what happens when go to admin_level=4?
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Fernando Trebien
+55 (51) 9962-5409

"Nullius in verba."

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