This repository contains clipping polygon for download.geofabrik.de.
They are used to create the regional extracts of the planet dump using osmium extract.
The format is documented on the OSM wiki.
This repository is published in order to allow you to track the changes to the clipping boundaries, and submit issues if you should find a bug.
In the polygons directory, you will find the polygons in (mostly) hierarchical order.
At the top level, there are continents (and Russia as intercontinental country, the US and Canada for historic reasons).
Below them you will find countries within continents, and states/provinces within their countries.
In addition, the top level directory contains some special clipping polygons which do not match a country or published extract
to split the world into few large subregions.
When the Geofabrik download server computes nightly OSM extracts, it does so in a hierarchical fashion. First the contients are created from the planet file, then the countries are cut from the continents, and so on.
Therefore, the clipping process does not have to know about boundaries where they coincide with a higher level boundary. For example, because the Southern border of Texas coincides with the border of the USA, and because Texas is cut from the USA file, this particular boundary only requires precise modelling in the USA polygon. In the Texas polygon, only those parts of the boundary that are inside the USA are modelled precisely, whereas the Southern border coarsely extends into Mexico - it doesn't matter since there will not be any data in that area when Texas is cut from the USA file.
Texas (bold red line) and USA (thin red line) clipping boundaries.
There is a tool in this repository called intersectpoly and we use this to create the smallest common area of several polygons, so that the polygons (or GeoJSON index files) we offer on the download server show the actual polygon contained in the extract. They will differ from the polygons in this repository.
See CONTRIBUTING.md for buffer sizes, degree of simplification, handling of exclaves etc.
Polygons are an OpenStreetMap produced work in terms of the Open Database License 1.0. When using them, you are required to attribute OpenStreetMap.
Software is released into the public domain.