@turf/polygonize

@turf/polygonize

polygonize

Polygonizes (Multi)LineString(s) into Polygons. Implementation of GEOSPolygonize function (geos::operation::polygonize::Polygonizer). Polygonizes a set of lines that represents edges in a planar graph. Edges must be correctly noded, i.e., they must only meet at their endpoints. (NOTE: while TurfJS has no specific function, an easy way to ensure this is to use the QGis library and call unaryUnion() on the set of input geometries and then pass the result to turf-polygonize). The implementation correctly handles:

• Dangles: edges which have one or both ends which are not incident on another edge endpoint.
• Cut Edges (bridges): edges that are connected at both ends but which do not form part of a polygon.

Parameters

• geojson (FeatureCollection | Geometry | Feature<(LineString | MultiLineString)>) Lines in order to polygonize

Examples

var lines = {
 "type": "FeatureCollection",
 "features": [
   {
     "type": "Feature",
     "properties": {},
     "geometry": {
       "type": "LineString",
       "coordinates": [
         [
           119.00390625,
           -22.024545601240337
         ],
         [
           120.58593749999999,
           -28.613459424004414
         ],
         [
           125.595703125,
           -32.99023555965107
         ],
         [
           133.330078125,
           -32.99023555965107
         ],
         [
           142.646484375,
           -30.977609093348676
         ],
         [
           142.294921875,
           -24.126701958681668
         ],
         [
           139.04296875,
           -16.299051014581817
         ],
         [
           128.84765625,
           -15.199386048559994
         ]
       ]
     }
   },
   {
     "type": "Feature",
     "properties": {},
     "geometry": {
       "type": "LineString",
       "coordinates": [
         [
           142.646484375,
           -30.977609093348676
         ],
         [
           132.451171875,
           -27.449790329784214
         ],
         [
           128.671875,
           -23.1605633090483
         ],
         [
           119.00390625,
           -22.024545601240337
         ]
       ]
     }
   }
 ]
}
var outPolygon = turf.polygonize(lines)
//addToMap
var addToMap = [lines, outPolygon];

• Throws Error if GeoJSON is invalid.

Returns FeatureCollection<Polygon> Polygons created

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install @turf/polygonize

Or install the Turf module that includes it as a function:

$ npm install @turf/turf