Geocoding is the ability to match an input string representing a location - such as an address - to geographical coordinates. Reverse geocoding is logically the opposite, matching geographical coordinates to names of places.
This is needed to set correct address for events, and more easily find events with geographical data, for instance if you want to discover events happening near your current position.
However, providing a geocoding service is quite expensive, especially if you want to cover the whole Earth.
To give an idea of what hardware is required to self-host a geocoding service, we successfully installed and used Addok, Pelias and Mimirsbrunn on a 8 cores/16GB RAM machine without any issues importing only French addresses and data.
To change geocoder backend, you need to add the following line in
config :mobilizon, Mobilizon.Service.Geospatial, service: Mobilizon.Service.Geospatial.Nominatim
Nominatimto one of the supported geocoders. Depending on the provider, you'll also need to add some special config to specify eventual endpoints or API keys.
For instance, when using
Mimirsbrunn, you'll need the following configuration:
config :mobilizon, Mobilizon.Service.Geospatial, service: Mobilizon.Service.Geospatial.Mimirsbrunn config :mobilizon, Mobilizon.Service.Geospatial.Mimirsbrunn, endpoint: "https://my-mimir-instance.tld"
List of supported geocoders¶
This is the list of all geocoders supported by Mobilizon. The current default one is Nominatim and uses the official OpenStreetMap instance.
When using the official Nominatim OpenStreetMap instance (default endpoint for this geocoder if not configured otherwise), you need to read and accept the Usage Policy.
Autocomplete is not possible using Nominatim, you'll obtain no suggestions while typing.
Several companies provide hosted instances of Nominatim that you can query via an API, for example see MapQuest Open Initiative.
config :mobilizon, Mobilizon.Service.Geospatial.Nominatim, endpoint: "https://nominatim.openstreetmap.org", api_key: nil
When using France's Addok instance at
api-adresse.data.gouv.fr (default endpoint for this geocoder if not configured otherwise), you need to read and accept the GCU (in French).
config :mobilizon, Mobilizon.Service.Geospatial.Addok, endpoint: "https://api-adresse.data.gouv.fr"
The default endpoint is limited to France. Geo coding outside of France will return an empty result. Moreover, as France is implicit for this endpoint, country is not part of the result. To conform to
Provider interface, this provider return "France" as the country.
If plugged to another endpoint, in another country, it could be useful to change the default country. This can be done in
change endpoint default country
config :mobilizon, Mobilizon.Service.Geospatial.Addok, endpoint: "https://another-endpoint.tld" default_country: "Country"
Photon is an Apache 2.0 licenced search engine written in Java and powered by ElasticSearch.
You can use the API for your project, but please be fair - extensive usage will be throttled. We do not guarantee for the availability and usage might be subject of change in the future.
config :mobilizon, Mobilizon.Service.Geospatial.Photon, endpoint: "https://photon.komoot.de"
Pelias is a MIT licensed geocoder composed of several services written in NodeJS. It's powered by ElasticSearch.
config :mobilizon, Mobilizon.Service.Geospatial.Pelias, endpoint: nil
Mimirsbrunn is an AGPL-3.0 licensed geocoding written in Rust and powered by ElasticSearch.
config :mobilizon, Mobilizon.Service.Geospatial.Mimirsbrunn, endpoint: nil
Google Maps is a proprietary service that provides APIs for geocoding.
They don't have a free plan, but offer credit when creating a new account. See the pricing.
fetch_place_details tells GoogleMaps to also fetch some details on a place when geocoding. It can be more expensive, since you're doing two requests to Google instead of one.
config :mobilizon, Mobilizon.Service.Geospatial.GoogleMaps, api_key: nil, fetch_place_details: true
MapQuest is a proprietary service that provides APIs for geocoding.
They offer a free plan. See the pricing.
config :mobilizon, Mobilizon.Service.Geospatial.MapQuest, api_key: nil
More geocoding services¶
Geocoding implementations are simple modules that need to implement the
Mobilizon.Service.Geospatial.Provider behaviour, so feel free to write your own!