@turf/difference

What is @turf/difference?

@turf/difference is a module in the Turf.js library that allows you to compute the geometric difference between two polygons. This is useful in geospatial analysis for determining the area that is unique to one polygon when compared to another.

What are @turf/difference's main functionalities?

Compute Difference Between Two Polygons

This feature allows you to compute the difference between two polygons. The resulting polygon represents the area that is unique to the first polygon when compared to the second polygon.

const turf = require('@turf/turf');

const polygon1 = turf.polygon([[
  [-82.574787, 35.594087],
  [-82.574787, 35.615581],
  [-82.545261, 35.615581],
  [-82.545261, 35.594087],
  [-82.574787, 35.594087]
]]);

const polygon2 = turf.polygon([[
  [-82.560024, 35.585153],
  [-82.560024, 35.602602],
  [-82.52964, 35.602602],
  [-82.52964, 35.585153],
  [-82.560024, 35.585153]
]]);

const difference = turf.difference(polygon1, polygon2);
console.log(difference);

Other packages similar to @turf/difference

jsts

JSTS is a JavaScript library of spatial predicates and functions for processing geometry. It is a port of the Java Topology Suite (JTS). JSTS provides a more comprehensive set of geometric operations compared to @turf/difference, including union, intersection, and buffer operations.

martinez-polygon-clipping

Martinez Polygon Clipping is a library for performing boolean operations on polygons, such as union, intersection, and difference. It is known for its performance and accuracy, making it a good alternative to @turf/difference for complex polygon operations.

README

@turf/difference

difference

Finds the difference between two polygons by clipping the second polygon from the first.

Parameters

• polygon1 Feature<(Polygon | MultiPolygon)> input Polygon feature
• polygon2 Feature<(Polygon | MultiPolygon)> Polygon feature to difference from polygon1

Examples

var polygon1 = {
  "type": "Feature",
  "properties": {
    "fill": "#F00",
    "fill-opacity": 0.1
  },
  "geometry": {
    "type": "Polygon",
    "coordinates": [[
      [-46.738586, -23.596711],
      [-46.738586, -23.458207],
      [-46.560058, -23.458207],
      [-46.560058, -23.596711],
      [-46.738586, -23.596711]
    ]]
  }
};
var polygon2 = {
  "type": "Feature",
  "properties": {
    "fill": "#00F",
    "fill-opacity": 0.1
  },
  "geometry": {
    "type": "Polygon",
    "coordinates": [[[126, -28], [140, -28], [140, -20], [126, -20], [126, -28]]]
  }
};

var difference = turf.difference(polygon1, polygon2);

//addToMap
var addToMap = [polygon1, polygon2, difference];

Returns (Feature<(Polygon | MultiPolygon)> | undefined) a Polygon or MultiPolygon feature showing the area of polygon1 excluding the area of polygon2 (if empty returns undefined)

removeEmptyPolygon

Detect Empty Polygon

Parameters

• geom Geometry<(Polygon | MultiPolygon)> Geometry Object

Returns (Geometry<(Polygon | MultiPolygon)> | undefined) removed any polygons with no areas

---

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/difference

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

$ npm install @turf/turf

Changelog

4.5.0

🚀 New Modules

• @turf/clusters Takes a set of points and partition them into clusters using the k-means clustering algorithm. (PR https://github.com/Turfjs/turf/pull/787 - Author @stebogit )

• @turf/boolean-disjoint Boolean-disjoint returns (TRUE) if the intersection of the two geometries is an empty set. (PR https://github.com/Turfjs/turf/pull/805 - Author @rowanwins)

• @turf/boolean-contains Boolean-contains returns True if the second geometry is completely contained by the first geometry. The interiors of both geometries must intersect and, the interior and boundary of the secondary (geometry b) must not intersect the exterior of the primary (geometry a). Boolean-contains returns the exact opposite result of the @turf/boolean-within. (PR https://github.com/Turfjs/turf/pull/797 - Author @rowanwins)

• @turf/boolean-crosses Boolean-Crosses returns True if the intersection results in a geometry whose dimension is one less than the maximum dimension of the two source geometries and the intersection set is interior to both source geometries. Boolean-Crosses returns t (TRUE) for only multipoint/polygon, multipoint/linestring, linestring/linestring, linestring/polygon, and linestring/multipolygon comparisons. (PR https://github.com/Turfjs/turf/pull/796 - Author @rowanwins)

• @turf/boolean-clockwise Takes a ring and return true or false whether or not the ring is clockwise or counter-clockwise. (PR https://github.com/Turfjs/turf/pull/789 - Authors @morganherlocker @stebogit)

• @turf/clone Prevents GeoJSON coordinates from being mutated, similar to JSON.parse(JSON.stringify(geojson)). Only cloning the coordinates can be 3x-20x faster than the parse + stringify approach. (PR https://github.com/Turfjs/turf/pull/824 - Author @DenisCarriere)

🏅 New Features/Enhancements

• convertArea Converts a area to the requested unit. (PR https://github.com/Turfjs/turf/pull/821 - Author @wnordmann)
• Adds mask option to @turf/point-grid (PR https://github.com/Turfjs/turf/pull/791)
• New @turf/isolines based on MarchingSquares.js (PR https://github.com/Turfjs/turf/pull/781)
• Use ES6 modules / Add module.js to @turf/turf (PR https://github.com/Turfjs/turf/pull/793)
• Create-new-module script (PR https://github.com/Turfjs/turf/pull/823)

🐛 Bug Fixes

• Buffer - Drop circle buffer operation (PR https://github.com/Turfjs/turf/pull/786)
• Fixes @turf/idw bad property name #774 (PR https://github.com/Turfjs/turf/pull/800)
• Fix for @turf/polygon-tangents - Resolves #785 (PR https://github.com/Turfjs/turf/pull/792)