Dutch Centre is calculated with centroid because level-10 has no admin_centres defined. #14
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This reverts commit 41ebec8.
In commit 41ebec8, merged through PR #13 the admin level for the Netherlands is set to 10 for "city". This causes very unfortunate and often plain wrong "centers" to be defined. Since nearly no level-10 have an admin_centre but all level-8 do.
I suggest reverting the commit, because that
The correct levels are explained in the OSM wiki: the Netherlands uses 8 for city (municipality) and 10 for "villages and cities": https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative#11_admin_level_values_for_specific_countries
Level 8 have a manually set "center" relation, being where the administrative seat of that municipality is located. Level 10 hardly never has this¹
Downside of using level-8 for city is that this excludes a lot of places which are not "official" cities but are used in daily use a lot. As above: no-one would search for "Stichtse Vecht", everyone would search for "Houten" instead.
Downside of using level-10 for city is that many "cities" now appear twice in the dataset: once as municipality (level 8, with correct centre) and once as level 10 (without centre).
The error is apparent in e.g. Haarlem:
Red is the centroid, green is where the actual centre is as defined in admin_level=8. The centroid is used because like nearly all places on admin_level=10, Haarlem has no admin_centre relation.
Both "haarlem" relations can be seen on OSM:
This also causes the same "wrong centre" in Qwant maps: https://www.qwant.com/maps/place/admin:osm:relation:2712154@Haarlem#map=11.86/52.3898421/4.6062086
(Sigh. how hard is it to contain our messy Real World in clean models :D)
¹ Large cities such as Amsterdam, Rotterdam, The Hague and Utrecht have, historically, been tagged "wrong" but kept that way, so they often have a manually defined centre on admin_level=10.