OpenStreetMap
A few days ago, I asked the community about converting general GIS polygons into OSM multipolygon relations. I’ve searched online but haven’t found a workflow that fits my needs. Specifically, I am looking for a way to handle three different levels of administrative boundaries where adjacent areas share a single boundary line connected via a relation.
My question on the OSM forum is still awaiting a solution: Link
However, someone from my local community mentioned that what I’m looking for is “topology.” While that is a broad GIS term, they clarified that TopoJSON is a specific format designed for this. There are many converters available to turn GeoJSON into TopoJSON.
Interestingly, I found that someone opened a ticket for a TopoJSON converter in JOSM back in 2020, but it hasn’t received a response yet: Link
Discussion
Comment from Zkir on 11 April 2026 at 11:41
There is no such tool and most probably newer will. There is a strong belief in the OSM community that you should not automatically upload arbitrary data, especially complex one. Even when your are importing something from license-compatible source, you should understand what you are doing and how the new data corresponds with data already in osm, to avoid duplications.