simplify-geojson

Apply Ramer–Douglas–Peucker line simplification to GeoJSON features or feature collections in JS or on the CLI.

This module uses https://github.com/seabre/simplify-geometry for the simplification and wraps it in a interface for easily simplifying GeoJSON.

Install

npm install simplify-geojson

Usage

CLI

1cat data.geojson | simplify-geojson -t 0.01

Tolerance is specified by either -t or --tolerance and is a number in degrees (e.g. lat/lon distance). 1 degree is roughly equivalent to 69 miles. the default is 0.001, which is around a city block long.

JS

1var simplify = require('simplify-geojson')
2var simplified = simplify(geojson, tolerance)

geojson can be any of the following:

• Feature with a LineString
• Feature with a MultiLineString
• Feature with a Polygon
• Feature with a MultiPolygon
• FeatureCollection with any of the above

All segments in any of the supported types will be simplified (including holes in polygons, for instance).

Examples

Convert a CSV with lat/lon columns into geojson, then simplify that geojson, then open it in geojson.io (CSV is from my GPS logger and was my bike commute this morning):

1npm install simplify-geojson geojsonio-cli csv2geojson -g
2curl https://raw.github.com/maxogden/simplify-geojson/master/test-data/oakland-route.csv | \
3  csv2geojson --lat "LATITUDE N/S" --lon "LONGITUDE E/W" --line true | \
4  simplify-geojson -t 0.001 | \
5  geojsonio

Simplify alaska's border outline and count the number of lines of the simplified geojson output (tweak -t to see how it affects length):

1curl https://rawgit.com/johan/world.geo.json/master/countries/USA/AK.geo.json | \
2  simplify-geojson -t 0.01 | \
3  wc -l

Contributing

Contributors welcome! Please read the contributing guidelines before getting started.

License

BSD-2-Clause