This is the backend that serves map tiles and data for the election map which is deployed at https://elections.adrianfrith.com/. The repository for the frontend is at https://github.com/afrith/election-map-frontend.

The service provides Mapbox Vector Tiles (MVTs) for five levels of electoral geography: province, district council, municipality, ward, and voting district. The tiles include selected data points from the election results for ease of rendering. The tiles are provided at URLs of the form /tiles/{level}_{election}/{z}/{x}/{y}/tile.mvt, where:

• {level} is one of "prov", "dist", "muni", "ward" or "vd", corresponding to the five levels of electoral geography listed above.
• {election} is be one of "npe2004", "npe2009", "npe2014" or "npe2019".

The service also provides an endpoint to fetch full details of election results for any electoral geography as a JSON document. This endpoint is provided at URLs of the form /{election}/{ballot}/{level}/{code}, where:

• {level} and {election} are as described above.
• {ballot} is either "nat" or "prov", for the national and provincial ballot results respectively.
• {code} is the unique code identifying a geography, which can also be found in the code property of objects in the MVTs.

• Data store
  • PostgreSQL
  • PostGIS
• Service
  • Node.js
  • Express.js
  • TileStrata
  • tilestrata-postgismvt slightly modified (see repo)

To run the service you need the data, which can be downloaded here as a 1.5GB PostgreSQL dump file. Then you need to set three environment variables.

• DATABASE_URL is the URL of the PostgreSQL database (e.g. postgres://localhost/election-results).
• TILECACHE_DIR is the location of a directory to use to cache MVTs - since the data is unchanging the tiles never expire; if you need to clear the cache, delete the contents of this directory.
• PORT is the port on which the service will listen (defaults to 3000).

Then you can run yarn build && yarn start to run the service.