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Don't Forget to Reproject Spatial Data when Exporting to GeoJSON

In the process of working on a recent choropeth piece for work, I discovered that it’s easy to stumble when moving spatial data out of R and onto the web. It’s a poorly-documented reality that many web-based mapping libraries (including both D3 and Leaflet) expect GeoJSON data to be in EPSG:4326, and it is by no means a given that that your spatial data will start off in this projection.

If you’re like me and do your spatial data pre-processing in R before exporting to GeoJSON, you may have to re-project your data before these libraries will handle them properly. Thankfully, this is fairly easy to do with the modern spatial packages.

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