Convert GeoJSON to TopoJSON

Question

Question

How do you convert GeoJSON data to TopoJSON?

Why

Most likely, because you want a smaller file size. From the TopoJSON docs:

TopoJSON eliminates redundancy, allowing related geometries to be stored efficiently in the same file.... As a result, TopoJSON is substantially more compact than GeoJSON. The above shapefile of U.S. counties is 2.2M as a GeoJSON file, but only 436K as a boundary mesh, a reduction of 80.4% even without simplification.

Also, TopoJSON allows you to incrementally simplify a dataset, if you wish to.

Answer 1

Glad you asked, oh handsome OP.

Steps

For Mac OSX 10.8, assumes the installation of homebrew.

1. Install node.js: brew install node.js
2. Install topojson under node: npm install -g topojson
3. Convert the data: topojson -o output_file.json input_file.json