Mapshaper is a program for simplifying cartographic lines while preserving the topological relationships between adjacent polygons and intersecting polyline paths. It can read and write Shapefile, GeoJSON and TopoJSON files. You can find the current version online at mapshaper.org.
Mapshaper requires Node.js.
With Node installed, you can install the latest release version from the npm registry. Install with the "-g" flag to make the executable scripts available systemwide.
npm install -g mapshaper
To install and run the latest development code from github:
git clone git@github.com:mbloch/mapshaper.git
cd mapshaper
npm install
bin/mapshaper-gui # use the web interface locally
bin/mapshaper # use the command line tool
The mapshaper distribution includes the script mapshaper-gui, which runs mapshaper's web interface locally. You can also visit mapshaper.org to use mapshaper online. All processing is done in the browser, so user data stays private.
Browser compatibility: mapshaper works in recent versions of Chrome and Firefox as well as IE 10+. Exporting is not supported in Safari. Firefox seems better able to handle large files (say >200MB) than other browsers without encountering out-of-memory errors.
The mapshaper script runs well in OS X and has also been used successfully on Ubuntu 13.04 and Windows 8.
$ mapshaper -p 0.1 --repair counties.shp Retain 10% of removable vertices using default simplification and remove line intersections.
$ mapshaper -i 100 states.shp --dp Remove features smaller than ~100 meters using Douglas-Peucker simplification.
$ mapshaper -h Read a help message.
You will need to regenerate mapshaper.js if you edit any of the files in the src/ or lib/ directories. Run $ build to update mapshaper.js (used by the command line tool); run $ build gui to update www/mapshaper.js (used by the web interface).
$ build [gui] -f continuously monitors source files and regenerates mapshaper.js whenever a source file is modified.
Run $ mocha in the project directory to run mapshaper's tests.
This software is licensed under the MPL 2.0
According to Mozilla's FAQ, "The MPL's "file-level" copyleft is designed to encourage contributors to share modifications they make to your code, while still allowing them to combine your code with code under other licenses (open or proprietary) with minimal restrictions."
Thanks to Shan Carter for help designing mapshaper's web interface :)
And thanks to Mark Harrower for supporting development of the original MapShaper program at the University of Wisconsin – Madison.
To suggest improvements, add an issue.