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Overpass: Get a geometry of a location by name

I am given a ISO 3361 Alpha-2 country code and a location name.

I'm trying to use Overpass to extract the geometries (or boundaries, or polygon) of that location. I don't know the location's specific administrative level (i.e. it could be a town, a city, a county, etc..., but not any lower resolution/division than that).

For example: DE + berlin DE + munich US + chicago FR + Levroux

Tried the following query, but got way more data than I need: (rel[boundary="administrative"][name="Berlin"][admin_level="4"];>;);(._;>;);out;

or {{geocodeArea:"DE"}}->.a; ( nwr["name:en"="Berlin"][boundary=administrative][type=boundary][admin_level="4"](area.a); ); out geom; I exported it as Geojson and projected it on map, but besides getting the boundaries of Berlin (type=boundary), I got some more nodes that I wasn't expecting.

So what is the best way to extract this data? Thanks!

overpass polygon name

asked 31 Jan '21, 13:29

RamidAshar
11●1●1●2
accept rate: 0%

Was "some more nodes" just the admin_centre node or actual nodes of the relation? Explain what "projected it on map" means? What map? uMap?

(31 Jan '21, 16:54) DaveF

yes, thats probably it (the admin_centre), but even more nodes in some weird places (some in the middle of the city, some on the boundaries). I converted to GeoJson and put it on kepler.gl for instance. maxerickson's answer seems to solve this issue for me.

(31 Jan '21, 17:40) RamidAshar

2 Answers:

One way is to use explicit steps to fetch the ways and nodes instead of out geom:

{{geocodeArea:"DE"}}->.a;
nwr["name:en"="Berlin"][boundary=administrative][type=boundary][admin_level="4"](area.a);
out;
(way(r);
 >;);
out skel;

The way(r); line fetches only the ways from the boundary relation, and then out skel; fetches the nodes without their tags.

answered 31 Jan '21, 15:22

maxerickson
12.7k●10●83●176
accept rate: 32%

interesting. yes, it works. I got only the boundaries I needed. 1. Also, limiting to {{geocodeArea:"DE"}} seems to be really slow (I guess because the extra calls to OSM geocoding?) 2. Say I wanted all cities in Germany, should I simply remove the ["name:en"="Berlin"] part? (query goes timeout on UI).

(31 Jan '21, 17:43) RamidAshar

admin_level=4 is not for cities, so you'd have to do more than remove the name.

(31 Jan '21, 18:55) maxerickson

@maxerickson For some reason, back in 2012 This relation was defined as place=state

(06 Feb '21, 06:06) DaveF

Yes, it's a reflection of the political organization of Berlin. https://en.wikipedia.org/wiki/Berlin#Government

(06 Feb '21, 15:41) maxerickson

Have you got 'Don't display small features as POIs.' under Settings>Map turned off?

Checking only for relations will return only relations & speed the search up a bit.

area["ISO3166-1"=DE]; // Germany
rel["name:en"=Berlin][type=boundary](area);
way(r);
out geom;

PS Could you use the Code button when posting a routine. It makes it easier to read & copy/ppate/

answered 06 Feb '21, 05:06

DaveF
3.3k●84●98●133
accept rate: 16%