Polygons of certain countries like e.g. Austria not closed

docP · 2024-06-24T15:51:30.541Z

Hi,

during my last area creation round for overpass API I faced the probem that some country areas were not created, e.g. the one for Austria.
After some analysis I found that the parity check that is performed by overpass’ make_area command fails for these countries, which indicates that the polygons of the corresponding country relations is not closed ( Austria has 2 terminal nodes).
The applied database excerpt was europe-lastest.bz2 as of Jum 18th 24 provided by geofabrik and latest overpass version 0.7.62.

Any help or comment highly appreciated!

SekeRob · 2024-06-24T16:08:07.099Z

There’s bunches of countries with boundary highlighting in the OSM Inspector ‘Areas’ view
Noticed that island of Sardegna sprung up and dropped a note to the last one touching the boundary relation of France of which the island is part.

docP · 2024-06-24T19:39:16.565Z

Thanks for the interesting replies.

If in case of Austria (and maybe others) such terminal points in the borderline are no errors but in fact wanted / necessary, that would mean that the parity check in overpass’ make_area command needs to be updated. With the current implementation such relations are not considered in area creation.

BR

Hungerburg · 2024-06-24T22:28:32.196Z

Funny, I can easily query overpass for "foo=bla" in Austria. How do they themselves create the areas?

docP · 2024-06-25T08:53:01.083Z

Yes, that’s true. I came across this question myself and raised it in the overpass forum. A contributor gave the explanation that areas are regularly updated in the database, rather than recreated from scratch.
So if an area could be created with some earlier version of the osm data (and that’s definitely true with Austria according to my own experience) the area reamains in the overpass database even though it could not be created.

BR

docP · 2024-06-25T15:55:45.529Z

Checked once more with most recent database and a source code debugger.
The critical point for Austria seems to be this one:

node id=“11285980151” lat=“48.7695879” lon=“13.8663112”>
tag k=“historic” v=“boundary_stone”/>
tag k=“inscription” v=“I/5-4”/>
tag k=“name” v=“I/5-4”/>
tag k=“ref” v=“I/5-4”/>
/node>

It’s located at the Austrian-Czech border. Could it be that it was added erroneously to the borderline or in a wrong way as a terminal rather than connecting node?