olicarbo / osmtogeojson

convert osm to geojson

osmtogeojson

Converts OSM data to GeoJSON. Try the demo!

• stable
• real OSM polygon detection
• proper OSM multipolygon support
• full support for extended Overpass API geometry modes
• well tested and proven
• fast

This code is used in and maintained by the overpass turbo project.

Usage

• as a command line tool:

    $ npm install -g osmtogeojson
    $ osmtogeojson file.osm > file.geojson
  

  When working with extra large data files (≳ 100 MB) it is recommended to run the programm with a little extra memory to avoid process out of memory errors. The easiest way to do this is by running the command as node <path-to-osmtogeojson> and setting the --max_old_space_size=… parameter to the available memory size in MB (osmtogeojson typically needs about 4-5 times the input data size):

    $ node --max_old_space_size=8192 `which osmtogeojson` large.osm > large.geojson
  

• as a nodejs library:

    $ npm install osmtogeojson
  
    var osmtogeojson = require('osmtogeojson');
    osmtogeojson(osm_data);
  

• as a browser library:

    <script src='osmtogeojson.js'></script>
  
    osmtogeojson(osm_data);
  

API

osmtogeojson( data, options )

Converts OSM data into GeoJSON.

• data: the OSM data. Either as a XML DOM or in OSM JSON.
• options: optional. The following options can be used:
  • flatProperties: If true, the resulting GeoJSON feature's properties won't be a structured json object rather than a simple key-value list.
  • uninterestingTags: Either a blacklist of tag keys or a callback function. Will be used to decide if a feature is interesting enough for its own GeoJSON feature.
  • polygonFeatures: Either a json object or callback function that is used to determine if a closed way should be treated as a Polygon or LineString. read more

The result is a javascript object of GeoJSON data:

GeoJSON

The GeoJSON produced by this library will include exactly one GeoJSON-feature for each of the following OSM objects (that is everything that is also visible in overpass turbo's map view):

• all unconnected or interesting tagged nodes (POIs)
• all ways (except uninteresting multipolygon outlines)
• all multipolygons (simple multipolygons with exactly one closed outer way are present via their outer way)

All data is given as a FeatureCollection. Each Feature in the collection has an id property that is formed from the type and id of the original OSM object (e.g. node/123) and has the member properties containing the following data:

• type: the OSM data type
• id: the OSM id
• tags: a collection of all tags
• meta: metainformaton about the feature (e.g. version, timestamp, user, etc.)
• relations: an array of relations the feature is member of. Each relation is encoded as an object literal containing the following properties: role (membership role), rel (the relation's id) and reltags (contains all tags of the relation)
• tainted: this flag is set when the feature's geometry is incomplete (e.g. missing nodes of a way or missing ways of a multipolygon)

If the option flatProperties is set to true, the properties object will not contain any nested object literals, but directly provide a concise id, meta data and the tags of the respective OSM object.