README.md

turf-concave

turf concave module

turf.concave(points, maxEdge, units)

Takes a FeatureCollection of Point features and returns a concave hull.

Internally, this implements a Monotone chain algorithm.

Parameters

parameter	type	description
points	FeatureCollection	a FeatureCollection of Point features
maxEdge	number	the size of an edge necessary for part of the hull to become concave (in miles)
units	String	used for maxEdge distance (miles or kilometers)

Example

var points = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.601226, 44.642643]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.591442, 44.651436]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.580799, 44.648749]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.573589, 44.641788]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.587665, 44.64533]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [-63.595218, 44.64765]
      }
    }
  ]
};

var hull = turf.concave(points, 1);

var resultFeatures = points.features.concat(hull);
var result = {
  "type": "FeatureCollection",
  "features": resultFeatures
};

//=result

Returns Feature, a Polygon feature

Installation

Requires nodejs.

$ npm install turf-concave

Tests

$ npm test