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d3.jsgeojsontopojson

Using ONS maps with D3

I'm sorry this is probably a very basic issue, but I just can't seem to figure it out.

I wanted to map some data using D3.js and the map shape I wanted to use is provided by the UK's Office for National Statistics. I managed to get their geojson data to display, but as soon as I try to do anything with scaling, transforms, topojson, I've been a complete failure.

I've been through many, many, different approaches and I think it's something about the map data that is causing the issue. If I open the shape files in Mapshaper it looks perfect. If I export as geo or topojson and re-import, it looks perfect. If I try to run geo2svg on the geojson export it produces a lot of data, but nothing visible. If I try to import the original shape file into mapstarter.com it produces a flat line. And if I put the topojson into the D3 v4 bounding example I end up with a load of random triangles.

So, can someone show me how do you get ONS mapping data such as http://geoportal.statistics.gov.uk/datasets/1bc1e6a77cdd4b3a9a0458b64af1ade4_3 to display in a d3 example such as https://bl.ocks.org/iamkevinv/0a24e9126cd2fa6b283c6f2d774b69a2?

Thanks

Solution

  • The data that you have linked to is projected. Mapshaper supports projected data, but using d3.geoProjection with projected data will result in no data being displayed in most situations. You need to ensure your data is in lat long pairs for proper display with a d3.geoProjection.

    Luckily, in Mapshaper you can reproject your data. Copy all the files of the shapefile into mapshaper, and in the console change the projection to wgs84 (unprojecting your data):

    proj wgs84

    This data is now easily displayed and manipulated using a d3.geoProjection. Here is an example using the data that you referenced. Also a screenshot:

    enter image description here

    Lastly: It is possible to display projected data as well, but this is much less common.