Mapshaper by mbloch is one of my favourite “swiss army knife”-tools if you need fast data reduction and topology first aid in polygon data handling. There a two versions of mapshaper. The first is a hosted webservice: www.mapshaper.org, where you can easily upload .shp-, GeoJson- or TopoJson-Files via drag&drop or folder selection. Afterwards you have to chose your simplification method (Douglas-Peucker, Visvalingam or modified Visvalingam) and some other options like “repair intersections”, “auto snap” and “prevent shape removal” and you’re ready to go.
The second mapshaper-version is for your command line (which make it scriptable – very nice!) and requires Node.js. Once installed, you can start working on your data and code your own scipts to convert data (e.g. .shp to geoJson), get data informations, simplificate with snapping and rounding, make data field calculations, filter, join and much more. The full command reference your get here: https://github.com/mbloch/mapshaper/wiki/Command-Reference.
What mapshaper does:
- File merge/combine
- Coordinate rounding and snapping
- Topology identification
- Table join
- Expression calculation
- Boundary classification
- Merge layers
My example of data simplification with mapshaper.org