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Data preprocessing

create GeoJSON and TopoJSON of Earthquakes

The input data is a .txt file with point coordinates. We need to convert this to a GeoJSON file in order to plot it over our maps. We can do this with Qgis or ogr2ogr

ogr2ogr -f geojson data/aardbevingen_NL.geojson CSV:data/2017_06_Aardbeving_NL.txt -oo X_POSSIBLE_NAMES=LON -oo Y_POSSIBLE_NAMES=LAT -oo KEEP_GEOM_COLUMNS=NO

In Qgis:

Add a Delimeted Text File into QGIS. Set point coordinates for the geometry definition. Set comma as seperator, or change all comma's to points. Set Layer CRS to WGS84, EPSG:4326.

Save as GeoJSON. COORDINATE PRECISION: 6

Create TopoJSON of Municipalities

Install the following software with ndjson:

npm install --global topojson-client ndjson-cli topojson-simplify topojson-server

  1. download the gemeenten from https://geodata.nationaalgeoregister.nl/cbsgebiedsindelingen/ows?request=GetFeature&Service=WFS&version=2.0.0&typename=cbsgebiedsindelingen:cbs_gemeente_2017_gegeneraliseerd&outputFormat=application/json&srsName=EPSG:4326&propertyName=statcode,statnaam,geom and save it as gemeenten2017.geojson.

  2. create intermediate ndjson, removing and renaming some attributes.

    ndjson-cat gemeenten2017.geojson | ndjson-split 'd.features'
    | ndjson-map 'd.id = +d.properties["statcode"].substring(2,6), d.properties["name"] = d.properties["statnaam"], delete d.properties["statcode"], delete d.properties["statnaam"], delete d.geometry_name, d' > gemeenten2017.ndjson

  3. create topojson from the geojson, simplifying geometry.

    geo2topo --quantization 1e5 --newline-delimited municipalities=gemeenten2017.ndjson
    | toposimplify -s 0.000000001 > gemeenten2017.topojson