My test data is the Watershed Boundaries from NHDPlusV2; the California-only NHDPlusV21_CA_18_WBDSnapshot_01.7z (89MB) and the national NHDPlusV21_NationalData_WBDSnapshot_Shapefile_01.7z (1.7GB).
Converting the smaller file to TopoJSON was a snap, just
The flags are to add some GeoJSON properties to the resulting data file.
Taking the default arguments, TopoJSON reduced my 89MB SHP file to a 9.3MB TopoJSON file. Not bad, particularly since the straight GeoJSON is 257MB. A lot of compression thanks to shared boundaries. But also quantization; by default the topojson tool quantizes data to 10,000 values…
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