_{An extension of GeoJSON that encodes topology!} 

TopoJSON

　　https://github.com/topojson/topojson

The TopoJSON Format Specification

 　　https://github.com/topojson/topojson-specification

TopoJSON Client

　　https://github.com/topojson/topojson-client

TopoJSON Simplify

　　https://github.com/topojson/topojson-simplify

something about topojson