[Tagging] admin_boundary with multiple levels / county free citys / Kreisfreie Staedte

Florian Lohoff f at zz.de
Tue Nov 5 17:38:51 UTC 2013


On Tue, Nov 05, 2013 at 04:55:42PM +0100, Pieren wrote:
> On Tue, Nov 5, 2013 at 4:22 PM, Florian Lohoff <f at zz.de> wrote:
> 
> > A fix would be an admin_level=6;8 on the boundary or duplicating
> > the relation.
> 
> I'm surprised you still have such questions in Germany. Your
> description is not clear since you don't explain what is on the way
> and what is on the relation. But I can tell how it *should* be : on

The way is irrelevant. The admin boundarys is a collection of ways,
be it waterways, highways or other ways making up the boundary.

The relation contains an admin_level=6 which is the level for Countys.
With the Kreisfreie Städte the name on _that_ relation is actually the
Citys name although the level would imply it to be the countys name.

So nominatim is right to show the name as the countys name as thats
exactly what has been tagged. But its not only the countys name
but more the citys name.

> the boudary way : put the highest admin level (thus, with the lowest
> numerical number). And create one relation per admin_level, obviously.

> What I guess is that the admin_level on the way is just used for
> rendering purpose, not by nominatim which should exclusively work with
> admin boundary relations or place nodes.

How would nominatim really find adresses belonging to a place/city? We
have been there in 2008 without any boundarys and it was a mess to
decide which place node this address belongs to - distance is not
a measure for choosing your place.

> For the "county free big city", simply don't create a relation with
> admin_level 6 but keep only the one exclusively for admin_level 8.

The point is that the administrative boundarys is one of level 6 AND
level 8.

- if you only put a level 8 on the relation you loose the information
  about the importance of the administrative city.
- if you only put a level 6 on the relation you loose the information
  about the city. A county will be the same as the countyless city which
  it isnt - and there is no way to tell if this is a county without any 
  fine grained boundarys or a countyless city.. This is what we have right now.
- If you create both relations e.g. 6 _and_ 8 in seperate relations its
  not easy to tell whether this is really a countyless city unless
  geometrically comparing the boundary.

So we need a better way to mark multi level admin boundarys.

	admin_level=6;8

could be a solution. Or a new tag like

	admin_level=6
	admin_level_low=8

or

	admin_level_range=6-8

Just brainstorming.

Flo
-- 
Florian Lohoff                                                 f at zz.de
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