Proposed contours of polling stations

Elements of context

Following the publication of the dataset Office of polling and addresses of their voters by INSEE from the REU (Repertoire Electoral Unique), [the Etalab department] and the team data.gouv.fr worked on the generation of contours of polling stations based on these data.

As indicated in INSEE’s blog note:

This database of geolocated addresses makes it possible to approach the “areas” or “contours” of polling stations, which correspond to the geographical area comprising all the addresses of the voters of the same polling station.

Precautions for use

The generation of these contours is therefore an approach, which has inaccuracies due to the nature of the data (the REU consists of addresses affiliated to a polling station but is not in itself a definition of geographical contours) and the method used. It is made available by the data.gouv.fr team to promote the reuse of INSEE source data but ** is not intended to be authoritative**.

Different methods may create different possible plots/interpolations, because the source data does not imply their uniqueness.

Methodology

Source code for generating these contours is available on Github. These are calculated from the method of Voronoi Diagrams applied to addresses and modeled on the contours of the French municipalities. This code is perfectible and any contribution is welcome (via a Github issue on the deposit of the source code).

Data format

The data are offered in GeoJSON format (geospatial data format commonly used to represent and exchange geographic information) and Pmtiles (mapping tiles format optimised for the storage and dissemination of geospatial map data).

The use of data in pmtile format makes it easy to source contours from a web page without having to load the entire database at once (loading is done only locally depending on a user’s position and zoom level). An example is proposed with the publication of an html file in the documentation of that dataset.

Updates

The data will be updated on an ad hoc basis when the source data published by INSEE is updated.