@turf/union
Advanced tools
@turf/union is a part of the Turf.js library, which is a powerful geospatial analysis library written in JavaScript. The @turf/union package specifically allows you to perform union operations on GeoJSON polygons, merging multiple polygons into a single polygon.
Union of Two Polygons
This feature allows you to merge two GeoJSON polygons into a single polygon. The code sample demonstrates how to create two polygons and then merge them using the `turf.union` function.
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 union = turf.union(polygon1, polygon2);
console.log(JSON.stringify(union));Union of Multiple Polygons
This feature allows you to merge multiple GeoJSON polygons into a single polygon. The code sample demonstrates how to create three polygons and then merge them sequentially using the `turf.union` function.
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 polygon3 = turf.polygon([[
[-82.554024, 35.580153],
[-82.554024, 35.595602],
[-82.52464, 35.595602],
[-82.52464, 35.580153],
[-82.554024, 35.580153]
]]);
let union = turf.union(polygon1, polygon2);
union = turf.union(union, polygon3);
console.log(JSON.stringify(union));JSTS is a JavaScript library of spatial predicates and functions for processing geometry. It is a port of the well-known Java Topology Suite (JTS). JSTS provides a wide range of geometric operations, including union, intersection, and difference. Compared to @turf/union, JSTS offers a more comprehensive set of geometric operations but may be more complex to use.
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. Compared to @turf/union, Martinez Polygon Clipping is more focused on boolean operations and may offer better performance for these specific tasks.
Takes two (Multi)Polygon(s) and returns a combined polygon. If the input polygons are not contiguous, this function returns a MultiPolygon feature.
Parameters
polygon1 Feature<(Polygon | MultiPolygon)> input Polygon featurepolygon2 Feature<(Polygon | MultiPolygon)> Polygon feature to difference from polygon1options Object Optional Parameters (optional, default {})
options.properties Object Translate Properties to output Feature (optional, default {})Examples
var poly1 = turf.polygon([[
[-82.574787, 35.594087],
[-82.574787, 35.615581],
[-82.545261, 35.615581],
[-82.545261, 35.594087],
[-82.574787, 35.594087]
]], {"fill": "#0f0"});
var poly2 = turf.polygon([[
[-82.560024, 35.585153],
[-82.560024, 35.602602],
[-82.52964, 35.602602],
[-82.52964, 35.585153],
[-82.560024, 35.585153]
]], {"fill": "#00f"});
var union = turf.union(poly1, poly2);
//addToMap
var addToMap = [poly1, poly2, union];
Returns Feature<(Polygon | MultiPolygon)> a combined Polygon or MultiPolygon feature
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.
Install this module individually:
$ npm install @turf/union
Or install the Turf module that includes it as a function:
$ npm install @turf/turf
6.2.0
After a bit of hiatus, TurfJS is resuming releases.
@turf/boolean-touches][boolean-touches]Determines if two features touch but do not intersect
@turf/boolean-valid][boolean-valid]Checks if the geometry is a valid according to the OGC Simple Feature Specification
@turf/quadrat-analysis][quadrat-analysis]Performs a quadrat analysis on a set of points
@turf/rectangle-grid][rectangle-grid]Creates a grid of rectangles from a bounding box
@turf/voroni][voronoi]Typescript types for the options parameter have been fixed (PR https://github.com/Turfjs/turf/pull/1424 - Author @stevage)
@turf/points-within-polygon][points-within-polygon]Typescript types around the Feature's Properties will now be preserved. (PR https://github.com/Turfjs/turf/pull/1761 - Author @rugheid)
@turf/rewind][rewind]Typescript types for the 'reverse' option are now correct. Previously it was misnamed as 'reversed'. (PR https://github.com/Turfjs/turf/pull/1786 - Author @jonnycornwell)
@turf/difference][difference]No longer publishes an .mjs file.
@turf/meta][meta]No longer publishes an .mjs file.
@turf/tag][tag]Add MultiPolygon support. (PR https://github.com/Turfjs/turf/pull/1996 - Author bryceroney)
@turf/centroid Don't visit first point twice when calculating centroid
(PR https://github.com/Turfjs/turf/pull/1894 - Author @rowanwins)
@turf/transform-translate Better handling of negative distances
(PR https://github.com/Turfjs/turf/pull/1895 - Author @rowanwins)
@turf/union, @turf/difference, @turf/intersect Use polygon-clipping library to fix correctness issues
(PR https://github.com/Turfjs/turf/pull/1916 - Authors @mbullington, @ngottlieb)
@turf/buffer Change default number of steps to 8, and actually support the steps option
(PR https://github.com/Turfjs/turf/pull/1931 - Author stevenchanin)
@turf/buffer Fix projection issues that produce undersized buffers at non-equatorial latitudes
(PR https://github.com/Turfjs/turf/pull/1956 - Author dyakovlev)
@turf/helpers Add runtime checks to point() method, fixing an API break
(PR https://github.com/Turfjs/turf/pull/1964)
@turf/boolean-overlap Better performance for MultiPoint geometries
(PR https://github.com/Turfjs/turf/pull/1910 - Author @mfedderly)
@turf/helpers Add hectares to convertArea
(PR https://github.com/Turfjs/turf/pull/1943 - Author @DanielJDufour)
@turf/great-circle Update Typescript types to support MultiLineString input
(PR https://github.com/Turfjs/turf/pull/1928 - Author kronick)
@turf/square-grid Clarify inputs
(PR https://github.com/Turfjs/turf/pull/1885 - Author @raphael-leger)
@turf/greater-circle Clarify properties option example
(PR https://github.com/Turfjs/turf/pull/1888 - Author @chris-catignani)
@turf/line-to-polygon no longer modifies its input unless the mutate option is true
(PR https://github.com/Turfjs/turf/pull/1879 - Author @MortenBirk)
@turf/unkink-polygon remove Number.prototype.modulo override
(PR https://github.com/Turfjs/turf/pull/1978)
FAQs
turf union module
The npm package @turf/union receives a total of 255,344 weekly downloads. As such, @turf/union popularity was classified as popular.
We found that @turf/union demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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