Greenvale NY (relation:174439)

Hi all,

I’m new to the OSM community (been awesome so far) and have been working on building some administrative area polygons (relations) for use in a personal project of mine. I’m currently working on grabbing the admin_level=8 relations in the state of New York. In doing so I’ve come across Greenvale, NY (relation:174439). My logic is failing because I’m unable to close the polygon properly since the first 2 member ways close before I get to the remaining ways.

Before I try to account for this I wanted to ask the community if this is standard or if this might be a mapping issue? I’ve cross checked with some other administrative boundary providers and in those worlds it is not two individual polygons. That said I’m assuming I should be able to handle these scenarios since this is what I’d imagine would be a similar use case for a country (e.g. United States).

Any info or guidance as to how I could/should mange this would be awesome!

For the sake of thoroughness some technical details below:

  1. Using Osmosis to filter pbf files and convert them to OSM XML
  2. Python to manipulate/parse OSM XML to identify relations and its boundaries to build GeoJSON


Hi all - in typing out my question I got myself to answer the question :).

Just need to build up the individual polygons and use type multi polygon for the GeoJSON.

Thanks! Happy mapping.


at first: The boundary polygon was not valid because of a topological error in the south west:

i fixed that:

next: editing boundary relations as a newbie is NOT recommended. You need experience in doing that and you should use JOSM as preferred editor.

btw: which osm userid are you working with? “Ngp3”?

Last: you may download boundaries using


Hi Walter - sorry, just realizing I was a little vague with regards to my use of the word “building”. I’m not editing or creating boundaries myself. I’m just downloading and using the OSM data to programmatically build the boundaries myself for use in a personal project.

Thanks for the info/response! Like I mentioned in the follow up to my post I actually figured out the problem immediately as I posted the question.

That said - I did just find this relation (Bethpage: 175589), which appears to be a combination of ways that does not close.

I’m not confident that I know how to close it properly, but passing along in case you believe you are able to.

no. i can’t because the changes are too old.


With searching ways in the OSM history of that region I found the missing ways and closed the outline of this and a neighbour relation.