PDOK-Leaflet and D3js

An example of how to use PDOK tiles with Leaflet and D3js. The choropleth map shows the percentage of single person households per neighbourhood in the city of Groningen.

Create GeoJSON

First you download the ESRI Shape file [Wijk- en Buurtkaart 2012] (http://www.cbs.nl/nl-NL/menu/themas/dossiers/nederland-regionaal/publicaties/geografische-data/archief/2013/2013-2012-b68-pub.htm) from Netherlands Statistics (CBS). The file with neighbourhood areas "buurt_2012_v1.shp" can be converted to GeoJSON using ogr2ogr. The variable "P_EENP_HH" represents the percentage of single person households:

ogr2ogr -f "GeoJSON" groningen.geojson -sql "SELECT 'BU_NAAM', 'BU_CODE', 'GM_NAAM', CAST('P_EENP_HH' AS integer) AS 'P_EENP_HH' FROM 'buurt_2012_v1' WHERE 'GM_NAAM' = 'Groningen'" -t_srs "EPSG:4326" -s_srs "+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +towgs84=565.2369,50.0087,465.658,-0.406857330322398,0.350732676542563,-1.8703473836068,4.0812 +no_defs no_defs" buurt_2012_v1.shp

Inspect data for visualisation

In order to use the full value range in the choropleth map, use the ogrinfo utility to find the minimum and maximum values. Find the minimum value:

ogrinfo -sql "select min(P_EENP_HH) from buurt_2012_v1 where GM_NAAM = 'Groningen'" buurt_2012_v1.shp buurt_2012_v1

The minimum value is 7. Find the maximum value:

ogrinfo -sql "select max(P_EENP_HH) from buurt_2012_v1 where GM_NAAM = 'Groningen'" buurt_2012_v1.shp buurt_2012_v1

The maximum value is 84. The choropleth map uses the range from 0 to 85 for the classification.