Mapshaper is a specialist software for tasks like simplifying geodata, editing its attributes, format conversions, certain spatial overlay operations, filtering, and more. Mapshaper can be run on Windows, on macOS, and on Linux. Or users can use the online tool at mapshaper.org. Mapshaper supports various file formats, for example GeoJSON, TopoJSON, Shapefile, and CSV files with latitude and longitude information.
Mapshaper is actually a set of tools:
- the online tool at mapshaper.org
mapshaper-gui: runs the browser-based GUI of mapshaper.org locally on your machine, thus you don’t have to upload data to somebody else’s server to use the convencience of the GUImapshaper: runs the mapshaper commandsmapshaper-xl: same asmapshaperbut runs with more RAM to able to process larger files
Mapshaper particularly excels at simplification offering three algorithmus:
- Douglas-Peucker (or Poiker): run-of-the-mill, supported by most tools
- Visvalingam effective area
- Visvalingam weighted area
Mapshaper offers topologically consistent simplification. This means, simplification of polygonal data is done so that shared edges are simplified concordantly. What is great about the browser-based interface is that the degree of simplification can be chosen on a continuous scale and the tool shows the result interactively and also indicates how much of the data (vertices) would be removed at the current settings.
There is a Mapshaper wiki with tips how to use the tool and command reference for using the command line tools.