I am designing a map of very densely populated area in Tilemill. I am using OSM building data. Due to having a lot of buildings it is very difficult to differentiate one building to another.

Is there any way to reduce all building polygon sizes to 95% or 98% so that buildings can easily be differentiate each other?


1 Answer 1


A few thoughts:

  • simplest: remove borders at low zoom.

  • shrink via carto: use line-offset: <some small negative number> to inset the building border and remove the polygon-fill, though this can create strange artifacts around corners.

  • shrink via PostGIS: use ST_Buffer(way, <negative buffer in meters>. See ST_Buffer doc

Last one is probably the most robust solution, but ST_Buffer can be computationally expensive, and assumes you're pulling data in from a PostGIS database.

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