Small Discussion about Topojson?

Question

What is Topojson? 

TopoJSON is an extension of GeoJSON that encodes topology. Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called arcs. This technique is similar to Matt Bloch’s MapShaper and the Arc/Info Export format, .e00. 

TopoJSON eliminates redundancy, allowing related geometries to be stored efficiently in the same file. For example, the shared boundary between California and Nevada is represented only once, rather than being duplicated for both states. A single TopoJSON file can contain multiple feature collections without duplication, such as states and counties. Or, a TopoJSON file can efficiently represent both polygons (for fill) and boundaries (for stroke) as two feature collections that share the same arc mesh.

A TopoJSON file format is a format that encodes topology. TopoJSON is an extension of geoJSON. This format contains both geospatial data (arcs) and attribute data. In contrast to other GIS formats topoJSON uses arcs. Arcs are sequences of points, while line strings and polygons are defined as sequences of arcs. 

Each arc is defined only once, but can be referenced several times by different shapes, thus reducing redundancy and decreasing the file size. The topoJSON format is a format that is used by software like Microsoft PowerBI.

NPM Command

npm install topojson

Video for TopoJson