Wrong city tagging in some countries due to admin_level difference

[sander.vantulden@…]

Hi,

I found some roads in The Netherlands that have the wrong city associated with them. For example, if you take a street in the village called "Malden", ​Nominatim returns the corresponding village to be "Heumen", which is the municipality, but not the village.

It took me some time, but I think I found what could be the reason for this mistagging. In The Netherlands, the admin_level for city boundary is 10 and the municipality boundary is 8 (​see here for an explanation). This seems to be the other way around for other countries.

​Here is the "Heumen" city boundary relation (which holds the correct municipality boundary) and
​Here is the "Heumen" suburb boundary relation (which holds the correct city boundary)
​Here you can see that "Malden" also has a suburb boundary (which holds the correct city boundary). Because of the admin_level 10, "Heumen"'s admin_level 8 overrides it, to let it get the "Heumen" village tag.

Does this problem I describe make sense? Are country-specific admin_level tagging already handled in Nominatim? Or would it be possible to add it for specific countries?

This may be related to #5185, but I am not sure.

[sander.vantulden@…]

Changing it from minor to major for my use case. We found out that when using data in Belgium, the state that get's returned for places is not actually the correct state (province in this case). This is because Belgium maps it's state property to admin_level 6 instead of the usual level 4.

This is a big deal for us as we want to show the correct state (province) in our geocoding.

[lonvia]

Localizing admin_levels per country is on the TODO list but unfortunately there are more pressing matters at the moment. Patches are, as always, welcome.