Maps and geocoding

Decidim has the ability to geocode proposals and meetings and display them on a map. Decidim has built-in support for the following map service providers:

If you want to integrate Decidim to some other map service provider, read how to write your own integration code for that.

Configuring maps and geocoding

After generating your app, you’ll see that your config/initializers/decidim.rb file includes commented code about map services:

# Map and Geocoder configuration
# config.maps = {
#   ...
# }

The initializer comments provide examples for the services mentioned in this documentation. Please refer to the section below for the service you have registered for the maps functionality.

If you want to enable geocoding in your app:

  1. Select a service provider for the maps functionality and register an account with that provider

  2. Uncomment or add the code under the selected service provider in your config/initializers/decidim.rb.

  3. Make sure your config/secrets.yml file has the needed section (it should be added by the generator automatically).

  4. Configure the service provider credentials in config/secrets.yml and refer to them from your config/initializers/decidim.rb.

  5. If you had your Rails server running, restart it so the changes apply.

Configuring HERE Maps

Use the following configuration for HERE Maps:

config/initializers/decidim.rb:

# Map and Geocoder configuration
# == HERE Maps ==
config.maps = {
  provider: :here,
  api_key: Rails.application.secrets.maps[:api_key],
  static: { url: "https://image.maps.ls.hereapi.com/mia/1.6/mapview" }
}

config/secrets.yml:

default: &default
  # ...
  maps:
    api_key: <%= ENV["MAPS_API_KEY"] %>

.env:

MAPS_API_KEY=your_api_key_here

Configuring Open Street Maps based service providers

Use the following configuration for Open Street Maps based service providers:

config/initializers/decidim.rb:

# Map and Geocoder configuration
# == OpenStreetMap (OSM) services ==
config.maps = {
  provider: :osm,
  api_key: Rails.application.secrets.maps[:api_key],
  dynamic: {
    tile_layer: {
      url: "https://tiles.example.org/{z}/{x}/{y}.png?key={apiKey}",
      api_key: true,
      attribution: %(
        <a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap</a> contributors
      ).strip
      # Translatable attribution:
      # attribution: -> { I18n.t("tile_layer_attribution") }
    }
  },
  # static: { url: "https://staticmap.example.org/" }, # optional
  geocoding: { host: "nominatim.example.org", use_https: true },
  autocomplete: { url: "https://photon.example.org/api/" }
}

config/secrets.yml:

default: &default
  # ...
  maps:
    api_key: <%= ENV["MAPS_API_KEY"] %>

.env:

MAPS_API_KEY=your_api_key_here

For further information, see the service provider’s documentation or take a look at the Hosting your own map services section.

Combining multiple service providers

It is also possible to combine multiple service providers for the different categories of map services. For instance, if you want to use HERE Maps for the map tiles but host the other services yourself, use the following configuration:

# Map and Geocoder configuration
# == Combination (OpenStreetMap default + HERE Maps dynamic map tiles) ==
config.maps = {
  provider: :osm,
  dynamic: {
    provider: :here,
    api_key: Rails.application.secrets.maps[:here_api_key]
  },
  static: { url: "https://staticmap.example.org/" },
  geocoding: { host: "nominatim.example.org", use_https: true },
  autocomplete: { url: "https://photon.example.org/api/" }
}

config/secrets.yml:

default: &default
  # ...
  maps:
    here_api_key: <%= ENV["MAPS_HERE_API_KEY"] %>

.env:

MAPS_HERE_API_KEY=your_api_key_here

Disabling some of the map services

When using the maps functionality, you should always aim to provide all the services for the user that are available in Decidim. However, not all service providers provide all these services, so at times you may need to disable some of them.

The configuration syntax allows you to disable the map services one by one. For example, if you want to use HERE Maps as your default but disable the static map images and geocoding autocompletion functionality, you can use the following configuration:

config.maps = {
  provider: :here,
  api_key: Rails.application.secrets.maps[:api_key],
  static: false,
  autocomplete: false
}

Decidim works fine when some of the services are disabled individually but obviously, the disabled services are not available for Decidim users.

Global geocoder configurations

In the Dedicim initialiser (config/initializers/decidim.rb) you will also see a commented section for the global geocoder configurations commented as follows:

# Geocoder configurations ...
# config.geocoder = {
#   # geocoding service request timeout, in seconds (default 3):
#   timeout: 5,
#   # set default units to kilometers:
#   units: :km,
#   # caching (see https://github.com/alexreisner/geocoder#caching for details):
#   cache: Redis.new,
#   cache_prefix: "..."
# }

This will change the global geocoding settings for your application. To learn more about these settings, take a look at the Geocoder gem’s documentation.

Geocoding autocompletion configurations

Each autocompletion geocoder has their own configurations and this may not apply for all geocoding services. The geocoder autocompletion integrations shipped with Decidim support the configurations shown in this section.

If you want to customize the address format in the geocoding autocompletion fields, you can apply the following configuration to your geocoder settings:

config.maps = {
  # ... other configs ...
  autocomplete: {
    # For HERE:
    address_format: [%w(street houseNumber), "city", "country"]
    # For OSM/Photon:
    # address_format: ["name", %w(street housenumber), "city", "country"]
  }
}

Integrating with a new service provider

If you want to integrate the map functionality with a new service provider, take a look at the Custom map providers documentation.

Enabling maps and geocoding

Once the maps functionality is configured, you’ll need to activate it. As of April 2017, only proposals and meetings have maps and geocoding.

Proposals

In order to enable geocoding for proposals you’ll need to edit the component configuration and turn on "Geocoding enabled" configuration. This works for that specific component, so you can have geocoding enabled for proposals in a participatory process, and disabled for another proposals component in the same participatory process.

Meetings

Meetings do not have a configuration option for geocoding. Instead, if geocoding is configured it will try to geocode the address every time you create or update a meeting. As of April 2017 there is no way to enable or disable geocoding per meetings component.

Hosting your own map services

It is recommended to use a commercial service provider for all the map functionality to get up and running more easily. Hosting all these services yourself and keeping everything up to date is time consuming and rather complex. If the related complexity or the required time is not an issue, feel free to setup the following services on your own servers.

Map tiles: Open Street Maps tile server

You will need a map tiles server which is used for the dynamic maps that the user can move themselves.

Follow these instructions to setup your tiles server:

https://opentileserver.org/

In the example configuration, we assume you have used the following domain for the tiles server:

https://tiles.example.org

Static map images: Openstreetmap static maps server (osm-static-maps)

Some pages in Decidim display static map images which need to be fetched from an external server. The tiles server does not provide such static images by itself because one static map image may need multiple tiles to be combined into one. The static map image is therefore dynamically generated based on the parameters passed for the static map request (such as image dimensions and the geocoordinates of the map image position).

The Open Street Maps community has made multiple open source static maps image services from which you can pick freely but Decidim currently supports only osm-static-maps with the Open Street Maps services.

Follow these instructions to setup your static map images server:

https://github.com/jperelli/osm-static-maps#3-standalone-sample-server

In the example configuration, we assume you have used the following domain for the static maps image server:

https://staticmap.example.org

Setting up this service is optional. If you do not configure a static map URL for the OSM based map services, Decidim will use the dynamic map tiles to generate a similar map element.

Geocoding: Nominatim geocoding server

Nominatim makes it possible to place points on the Decidim maps based on addresses. This service provides geocoding capabilities by turning human readable addresses to geographic coordinates.

Follow these instructions to setup your geocoding server:

http://nominatim.org/release-docs/latest/admin/Installation/

In the example configuration, we assume you have used the following domain for the geocoding server:

https://nominatim.example.org

Geocoding autocompletion: Photon geocoding server

Photon makes it possible to provide the autocompletion service for people writing addresses to the address fields available in Decidim. It uses the Open Street Maps data to serve the autocompletion requests. When people select one of the suggested addresses, it will also tell Decidim the map point for that address.

Follow these instructions to setup your geocoding autocompletion server:

https://github.com/komoot/photon#installation

In the example configuration, we assume you have used the following domain for the Photon geocoding server for the autocompletion functionality:

https://photon.example.org

Configure Decidim

After you have all these services running, change your Decidim configurations to use these services. Read the Configuring Open Street Maps based service providers section for more information.