This example demonstrates how to simplify and clean geographic data by rounding coordinates within a TopoJSON file. It uses D3’s `d3.round` function to reduce each point’s precision to two decimal places, then outputs the cleaned result as a JSON string. The code maps over the nested structure of polygons, line strings, and points, applying the rounding operation at each coordinate level. The visualization gallery shows the transformed data as plain text, highlighting the coordinate simplification process. The source is a GeoJSON-derived TopoJSON file, processed entirely in the browser with D3 v3.