[Tagging] capital and state_capital: how are they being used in your country?

Fernando Trebien fernando.trebien at gmail.com
Mon May 19 00:27:34 UTC 2014

Oberallgäu is currently mapped as a political (not an administrative)
boundary, so Sonthofen would be neither a capital, nor an
administrative center of any relation. Correctly, its node has no
capital=* or admin_level=* tags.

Swabia, on the other hand, has its government seat in Augsburg, and
its node currently has no capital=* nor admin_level=* tags. Government
seat is not the same thing as a capital (as pointed out earlier), so
it seems correctly mapped too.

Bavaria, a state (admin_level=4), has it's capital Munich's node
tagged with capital=4, which seems to agree with the rule of tagging
the capital city as capital=[lowest admin level of all regions that
have it as capital]. If it were Germany's capital (as is Berlin), the
node would be tagged as capital=2 by this pattern.

However, capital=* and state_capital=* would also work to describe
this particular situation because government seat is not the same
thing as a capital (they often are the same city, but not always). So,
for the sake of clarity, I think it would be acceptable if we agreed
- we place capital=* on actual capitals (not any admin_centre), since
using numbers is more flexible than capital=yes and state_capital=yes
(equivalent to capital=2 and capital=4)
- what the admin_centre role refers to is a government seat, and in
some rare situations there may be more than one
- we define a "capital" role in administrative boundary relations for
those rare cases where capital and government seat are different

Also it seems that rendering programs are more concerned with the
concept of "capital" than "government seat", so it shouldn't be
necessary (at least not yet) to arrange another tag for nodes (such as
the capital tag) to identify them.

By this reasoning, Berlin's node would be tagged as capital=2 (as
would any country capital). And perhaps some rendering programs out
there (Mapnik/Carto, osmarender, and others) would need to be tweaked
to support this value.

Well, this is me thinking about all per country variations. In Brazil,
we would end up only using capital=2 for Brasília and capital=4 for
all state capitals. If capital=2 is not yet supported by apps, then
maybe we could copy Berlin temporarily (capital=yes+admin_level=2),
but at least knowing what the future tagging goal is. (We can just
leave a note on the node explaining that.)

On Sun, May 18, 2014 at 8:28 PM, Andreas Goss <andig88 at t-online.de> wrote:
> Am 5/18/14 14:43 , schrieb John Packer:
>> Honest question: are there capitals for something besides countries and
>> states?
>> If not, we could keep it simple:
>> * capital=yes for country capitals
>> * state_capital=yes for state capitals (already in use in some parts of
>> America <http://taginfo.openstreetmap.org/keys/state_capital#map>).
> See box on the right:
> https://en.wikipedia.org/wiki/Oberallg%C3%A4u
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Fernando Trebien
+55 (51) 9962-5409

"Nullius in verba."

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