Listing churches with their administrative location using Overpass

Question

I'd like to extract a list of churches from OSM with their name, their coordinates and the name of the lower administrative division they belong to. I managed to get the first ones with:

area["name"="Mayenne"]->.boundaryarea;
way(area.boundaryarea)["building"="church"];
out tags center;

I deliberately ignore nodes and relations as they don't seem relevant in this case.

I can't find a way to retrieve the name of the lower administrative division. Is there a way to do it?

Answer 1

Similar to an example in the Overpass by Example library, I'd suggest to use the following query:

[timeout:60];
area["name"="Mayenne"]->.boundaryarea;
way(area.boundaryarea)["building"="church"];
  foreach(
    node(w)->.n;
    .n is_in->.a;
    area.a[name][boundary=administrative][admin_level~"^[2-8]$"] -> .a;
    out center;
    convert way ::=::,
              ::id = id(),
              is_in=a.set("{" + t[admin_level] + ":" + t[name] + "}");

    out;
  );

Step-by-step explanation how this query works:

• It iterates over each building=church in your area
• determines all nodes for each building
• find out in which areas those nodes are (this is the actual georeferencing step)
• filter out all areas with boundary=administrative and admin_level between 2 and 8 (you can adjust those if needed).
• print out the center point of the church building way
• generates an artificial element with the same way id and an additional element is_in, which lists all administrative boundaries the church is in.
• prints out artificial element

Note that the query returns two ways for each church, one with a center node, and one with an is_in entry but without geometry. At this time, you have to manually merge those two ways. In a later version of Overpass API this will change, though, returning only one single result including geometry.

The line containing georeferencing information looks as follows:

<tag k="is_in" v="{2:France};{4:Pays-de-la-Loire};{6:Mayenne};{7:Château-Gontier};{8:Senonnes}"/>

Result is also available here for download: https://gist.github.com/mmd-osm/497252a37d174b187c7afc0238200fc5