Geospatial Capabilities

CKAN offers a powerful set of geospatial features that allow adding spatial information to your datasets.

Spatial metadata for datasets

All the features in this section are provided by the ckanext-spatial extension (check the README for requirements and installation).

  • Associate geographic data with datasets, with automatic geo-indexing of datasets (spatial_metadata plugin)

    When activated, this plugin allows users to associate a geometry with a CKAN dataset, by adding a GeoJSON extra value to the dataset with key spatial. For example:

    {"type":"Polygon","coordinates":[[[2.05827, 49.8625],[2.05827, 55.7447], [-6.41736, 55.7447], [-6.41736, 49.8625], [2.05827, 49.8625]]]}
    

    Or:

    { "type": "Point", "coordinates": [-3.145,53.078] }
    

    Datasets with spatial values are automatically geo-indexed, for example so that they can be searched using spatial filters.

    The spatial model requires the installation and configuration of PostGIS on your database backend, as described on the installation instructions.

  • Search for datasets using spatial queries (spatial_query plugin)

    Once your datasets are geo-indexed, you can perform spatial queries by bounding box, via the following API call:

    /api/2/search/dataset/geo?bbox={minx,miny,maxx,maxy}[&crs={srid}]
    

    Or, starting on CKAN 1.6, as part of the default search:

    POST http://localhost:5000/api/action/package_search
    {
        "q": "Pollution",
        "extras": {
            "ext_bbox": "-7.535093,49.208494,3.890688,57.372349"
        }
    }
    

    Check the documentation on the ckanext-spatial README for more details:

    https://github.com/okfn/ckanext-spatial#spatial-query

  • Add a map widget for spatial search queries (spatial_query_widget plugin)

    You can display a small map widget on the dataset search form, users can draw a rectangle on the map to add a spatial filter to their search queries.

    Check the documentation on the ckanext-spatial README for more details:

    https://github.com/okfn/ckanext-spatial#spatial-query-widget

http://i.imgur.com/WoEwR.png http://i.imgur.com/GYggu.png

Metadata Conventions

Over time some conventions have emerged for storing geospatial information as extra metadata fields in datasets. Follow these conventions when storing information in CKAN datasets, so that your datasets will easily integrate with CKAN extensions and built-in functions, such as the automatic geo-indexing of datasets. The following metadata keys are used:

  • spatial-text: Textual representation of the extent / location of the package
  • spatial: GeoJSON representation of the extent of the package (Polygon or Point)
  • spatial-uri: Linked Data URI representing the place name

For example:

* spatial-text: United Kingdom
* spatial: {"type": "Polygon", "coordinates": [[[0.50, 49.74], [0.5, 59.25], [-6.88, 59.25], [-6.88, 49.74], [0.50, 49.74]]]}
* spatial-uri: http://www.geonames.org/2635167

or:

* spatial-text: Matsushima
* spatial: {"type": "Point", "coordinates": [38.36, 141.07]}
* spatial-uri: http://www.geonames.org/2111964

CSW support

CKAN offers support for the Catalogue Service for the Web (CSW) standard. This support consist of:

  • Ability to harvest records from remote CSW servers (as well as individual documents available online or Web Accessible Folders of them). CKAN supports the ISO-19139 encoding.
  • Basic CSW interface (for the harvested records)

This is done via different extensions: ckanext-harvest (See Import (“Harvest”) Data from Other Sites) offers the harvesting infrastucture, ckanext-inspire implements the harvesters for CSW servers and ckanext-csw is required by the previous one and offers the CSW interface.

Please refer to the README files of these extensions for instructions on how to install and configure them.