Maps online invariably use the Web Mercator projection. The Dirty Reprojectors project aims to change that, at least in Mapbox. Anand Thakker explains.

Almost all web mapping libraries render maps using Web Mercator, making an assumption that you generally can’t change out-of-the-box. This has advantages, but it posed a real challenge for us when we set out to build the Washington Post’s live election results map, where using the Albers USA projection was an important requirement. To meet that requirement, we built a pipeline to pre-process geometries.

It’s a bit of a kludge, a way of fooling Mapbox into showing a different projection—latitude/longitude coordinates aren’t accurate any more—but it’s an impressive stab at a real problem. The Dirty Reprojectors web app demonstrates the possibilities, with all the projections available through the d3-geo and d3-geo-projection libraries. [James Fee]