In this chapter you explored one of D3's coolest features: geographical maps and projections, which is part of the d3-geo module.
Throughout this chapter we explored the main GIS data formats for Web-based vector maps: GeoJSON and TopoJSON. You learned how to read a GeoJSON file and display its shapes using d3.geoPath(), how to use a projection to place GeoJSON positions on a map, how to obtain GeoJSON features from TopoJSON data, merge shapes, create meshes and discover neighboring shapes. You also learned how to add graticules to a map, standard parallels, draw lines and circles.
A large section was dedicated to projections, one of the main features of the d3-geo module. D3 supports over a hundred projection functions in the d3-geo-projection and d3-geo-polygon modules. You learned how to distinguish different types of projections and how to select them based on...
