OSM Extract Polygon

This small and simple tool processes OSM pbf files to generate boundary polygons.

The main question it answers is: How do I extract the polygon of an administrative boundary?

In particular it looks for administrative boundaries (e.g., city boundaries, country boundaries, ...) and creates an output file per boundary that is in the Osmosis Polygon format.

Download

Just head over to the Releases and grab the version for your operating system (macOS, Linux, and Windows supported).

Usage

OSM Extract Polygon 0.1.4
Andreas <andreas.gemsa@googlemail.com>
Extracts administrative boundaries of OSM pbf files and produces polygon files compatible with Osmosis.

USAGE:
    osm_extract_polygon [OPTIONS] --file <file>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
    -f, --file <file>              input file
    -x, --max <max_admin_level>    max administrative level (can take value from 1-11) [default: 8]
    -m, --min <min_admin_level>    minimum administrative level (can take value from 1-11) [default: 8]

Example

osm_extract_polygon -f karlsruhe-regbez-latest.osm.pbf

The program will create a folder <INPUT_PBF_FILE>_polygons/ in the same folder where the input file is. This folder contains for each administrative boundary it found and extract a .poly file. The name of the file is the name of the administrative boundary relation, potentially prefixed by a prefix defined in the relation under the tag name:prefix.

For more information about the meaning of the minimum and maximum administrative level take a look into the OSM Wiki.

Use Case: Extracting a smaller OSM file of a city

Assume you want to have a small OSM file of a single city. The problem you might face is, that the smallest file you can get is still very large. The tool Osmosis can extract parts of an osm file when supplied with a Osmosis polygon file, but you don't have such a file (and manually creating one is burdensome).

In this example I will explain how to solve this problem for the city of Karlsruhe, Germany.

Preparation

Get the newest release of osm_extract_polygon from the release page.
Install Osmosis
Obtain a OSM pbf file that contains Karlsruhe: Go to geofabrik and download Karlsruhe Regierungsbezirk.

Execution

Run osm_extract_polygon:

./osm_extract_polygon -f karlsruhe-regbez-latest.osm.pbf

Verify that the program ran, a few hundred small *.poly files are in the folder karlsruhe-regbez-latest.osm.pbf_polygons/. The file you are interested in is Stadt_Karlsruhe.poly.
Run Osmosis:

osmosis --read-pbf file="karlsruhe-regbez-latest.osm.pbf" --bounding-polygon file="karlsruhe-regbez-latest.osm.pbf_polygons/Stadt_Karlsruhe.poly" --write-xml file="karlsruhe.osm"

The output osm file you are interested in is karlsruhe.osm.

morandd / osm_extract_polygon