@turf/flatten

What is @turf/flatten?

@turf/flatten is a module in the Turf.js library that is used to flatten any GeoJSON object into a FeatureCollection. This is particularly useful when dealing with complex nested geometries and you need to simplify them into a flat structure.

What are @turf/flatten's main functionalities?

Flattening a MultiPolygon

This code demonstrates how to flatten a MultiPolygon into a FeatureCollection of Polygons. The input is a MultiPolygon, and the output is a FeatureCollection with each Polygon as a separate feature.

const turf = require('@turf/turf');
const multiPolygon = turf.multiPolygon([[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], [[[20, 20], [30, 20], [30, 30], [20, 30], [20, 20]]]]);
const flattened = turf.flatten(multiPolygon);
console.log(flattened);

Flattening a MultiLineString

This code demonstrates how to flatten a MultiLineString into a FeatureCollection of LineStrings. The input is a MultiLineString, and the output is a FeatureCollection with each LineString as a separate feature.

const turf = require('@turf/turf');
const multiLineString = turf.multiLineString([[[0, 0], [10, 10]], [[20, 20], [30, 30]]]);
const flattened = turf.flatten(multiLineString);
console.log(flattened);

Flattening a GeometryCollection

This code demonstrates how to flatten a GeometryCollection into a FeatureCollection of individual geometries. The input is a GeometryCollection, and the output is a FeatureCollection with each geometry as a separate feature.

const turf = require('@turf/turf');
const geometryCollection = turf.geometryCollection([
  turf.point([0, 0]),
  turf.lineString([[10, 10], [20, 20]]),
  turf.polygon([[[30, 30], [40, 40], [50, 50], [30, 30]]])
]);
const flattened = turf.flatten(geometryCollection);
console.log(flattened);

Other packages similar to @turf/flatten

geojson-flatten

The geojson-flatten package provides similar functionality to @turf/flatten by flattening nested GeoJSON objects into simpler structures. It is a lightweight alternative but does not offer the extensive suite of geospatial analysis tools that Turf.js provides.

geojson-utils

The geojson-utils package offers various utilities for working with GeoJSON data, including flattening nested structures. While it provides some similar functionalities, it is more of a general-purpose toolkit for GeoJSON manipulation rather than a specialized library like Turf.js.

README

@turf/flatten

flatten

Flattens any GeoJSON to a FeatureCollection inspired by geojson-flatten.

Parameters

• geojson (FeatureCollection | Geometry | Feature<any>) any valid GeoJSON Object

Examples

var multiGeometry = turf.multiPolygon([
  [[[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]]],
  [[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0]],
  [[100.2, 0.2], [100.8, 0.2], [100.8, 0.8], [100.2, 0.8], [100.2, 0.2]]]
]);

var flatten = turf.flatten(multiGeometry);

//addToMap
var addToMap = [flatten]

Returns FeatureCollection<any> all Multi-Geometries are flattened into single Features

---

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/flatten

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

$ npm install @turf/turf

Changelog

4.7.0

🚀 New Modules

[@turf/projection][projection]

• toMercator: Converts a WGS84 GeoJSON object into Mercator (EPSG:900913) projection
• toWgs84: Converts a Mercator (EPSG:900913) GeoJSON object into WGS84 projection

(PR https://github.com/Turfjs/turf/pull/927 - Author @stebogit)

[@turf/point-to-line-distance][point-to-line-distance]

Returns the minimum distance between a {@link Point} and a {@link LineString}, being the distance from a line the minimum distance between the point and any segment of the LineString.

(PR https://github.com/Turfjs/turf/pull/925 - Author @stebogit)

[@turf/boolean-within][boolean-within]

Boolean-within returns true if the first geometry is completely within the second geometry. The interiors of both geometries must intersect and, the interior and boundary of the primary (geometry a) must not intersect the exterior of the secondary (geometry b). Boolean-within returns the exact opposite result of the [@turf/boolean-contains][boolean-contains].

(PR https://github.com/Turfjs/turf/pull/924 - Author @rowanwins)

🏅 New Features/Enhancements

• Updates [@turf/unkink-polygon][unkink-polygon] testing & added flattenEach instead of using flatten. (PR https://github.com/Turfjs/turf/pull/889)
• [@turf/concave][concave] refactoring, replacing [@turf/union][union] with geojson-dissolve to increase speed and added support to null geometries (PR https://github.com/Turfjs/turf/pull/907 - Contributor @stebogit @DenisCarriere)
• Adds doc note on [@turf/polygonize][polygonize] about "Edges must be correctly noded" (PR https://github.com/Turfjs/turf/pull/898 - Contributor @stebogit @NickCis)
• Adds support to foreign Members to [@turf/clone][clone] (PR https://github.com/Turfjs/turf/pull/904 - Contributor @DenisCarriere)
• Extends support of any GeoJSON to [@turf/simplify][simplify] (PR https://github.com/Turfjs/turf/pull/903 - Contributor @DenisCarriere @stebogit)
• Adds new isNumber function and improves type checking for few [@turf/helpers][helpers] methods (PR https://github.com/Turfjs/turf/pull/920 - Contributor @DenisCarriere @stebogit)
• Adds throw errors to invalid MultiPolygons for [@turf/simplify][simplify] (PR https://github.com/Turfjs/turf/pull/922 - Contributor @DenisCarriere)

🐛 Bug Fixes

• Fixes @turf/bbox-clip point intersection handling, adding sanity-checks the lineclip output (PR https://github.com/Turfjs/turf/pull/886)
• Fixes [@turf/line-split][line-split] endpoint case handling applying [@turf/truncate][truncate] on splitter (PR https://github.com/Turfjs/turf/pull/892 and https://github.com/Turfjs/turf/pull/855 - Contributor @stebogit)
• Fixes [@turf/intersect][intersect] throwing "uncaught exception", adding [@turf/truncate][truncate] to inputs and returning Feature<null> if no geometry (PR https://github.com/Turfjs/turf/pull/890 - Contributor @stebogit @vicvolk)
• Fixes [@turf/hex-grid][hex-grid] not properly cloning the last ring vertex (PR https://github.com/Turfjs/turf/pull/897 - Contributor @stebogit @DenisCarriere)
• Fixes [@turf/boolean-disjoint][boolean-disjoint] incorrect behaviour where a poly was completely contained within another poly (PR https://github.com/Turfjs/turf/pull/908 - Contributor @rowanwins)
• Fixes [@turf/simplify][simplify] process pending on particular geometries, applying [@turf/clean-coords][clean-coords] to input. (PR https://github.com/Turfjs/turf/pull/903 - Contributor @stebogit @DenisCarriere)
• Fixes boolean properties not being translated with [@turf/clone][clone] (PR https://github.com/Turfjs/turf/pull/909 - Contributor @DenisCarriere)
• Fixes [@turf/boolean-contains][boolean-contains] incorrect output when checking two polygons (PR https://github.com/Turfjs/turf/pull/923 - Contributor @rowanwins @DenisCarriere)