[Talk-us] administrative boundaries and Nominatim

Brian Quinion openstreetmap at brian.quinion.co.uk
Wed Aug 1 00:42:49 BST 2012


>> Is it sensible to have a polygon for the boundary and also a node that
>> locates precisely the cultural/logical center?  Does Nominatim ignore
>> the node when there is a same-named boundary?  Or is there some way to
>> have a relation for a town that has both a polygon and a center?
>
>  http://wiki.openstreetmap.org/wiki/Relation:boundary
>
> Apparently you can add a node to the relation with role admin_centre.

New version of nominatim supports both admin_centre and label relation
members although it will also have a go at automatically merging them
even if they are not explicitly tagged.

The 'label' member will be merged (name and tags), relation tags win
if there is a conflict.

'admin_centre' member will be merged only if the names and 'rank'
(effectively admin_level / place=*) match, but other than that same
rules.

In both cases the node will also be added as the centre point of the
polygon - i.e. the location that the map will centre on.  This is a
new property in the xml and json format and will be release with the
new version.

While doing this people may also wish to ensure that there is a
wikipedia tag [1] which is now used as a basis to calculate relative
importance of admin features.  Adding this makes the ordering of
results far better.

--
 Brian

[1] http://wiki.openstreetmap.org/wiki/Wikipedia



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