The centroid point data was uploaded separately and loaded directly to the Election map base.
Fortunately for the sake of our demo, the government provides GIS data for parliamentary constituencies free of charge from the Office for National Statistics.įor the Constituencies map, using a mixture of Avenza MaPublisher and QGIS software, we cleaned up the government’s dataset and produced centroid point data for labelling the constituencies.
Maps with interlocking polygons are some of the hardest to create because they need perfectly matching boundaries, and many map polygon datasets are extremely expensive because they are so time-consuming to produce and maintain. The UK’s 650 parliamentary constituencies are composed of interlocking polygons.
However, they can be processed with specialist GIS software and turned into a map image. GIS files contain raw data – code, not imagery. Geographical Information Systems (GIS) are all about the handling of coordinates and projection systems in formats such as shapefiles, geojson, geoTiffs and many others. This is one of the great features of Maproom’s constituencies map – you can zoom in and out to see great detail of constituency boundaries as well as the overview of the entire UK all in one map.Ģ – GIS data manipulated to create a layer of interlocking polygons for the parliamentary constituencies When the user zooms in deep to the map, the road network will show up on the Mapbox base. The coloured constituencies are going to be overlaying the land in a later step, so having a white landmass backdrop is essential for opacity effects, whilst the blue-grey sea needs to provide enough distinction from the semi-transparent constituencies to define them without overpowering their colours. It is at the cutting edge of geocoding development, in our view.įor the UK Constituencies Map we have started by styling a Mapbox base quite simply with white landmass and a fairly strong blue-grey for the sea. The best known is Google Maps, but our current favourite is Mapbox, which allows complex styling of OpenStreetMap (OSM) data and has a range of useful functions in its javascript API.
There are a number of online map services which can be manipulated by developers.