@turf/simplify

What is @turf/simplify?

@turf/simplify is a module within the Turf.js library that provides functionality to simplify GeoJSON geometries. It uses the Ramer-Douglas-Peucker algorithm to reduce the number of points in a geometry while retaining its overall shape. This can be useful for reducing the complexity of geometries for faster processing and rendering.

What are @turf/simplify's main functionalities?

Simplify a LineString

This feature allows you to simplify a LineString geometry. The `tolerance` parameter controls the level of simplification, and `highQuality` determines whether to use a slower, higher-quality algorithm.

const turf = require('@turf/turf');
const line = turf.lineString([[0, 0], [1, 1], [2, 2], [3, 3], [4, 4], [5, 5]]);
const simplified = turf.simplify(line, {tolerance: 0.01, highQuality: false});
console.log(simplified);

Simplify a Polygon

This feature allows you to simplify a Polygon geometry. Similar to the LineString example, you can control the simplification level with the `tolerance` parameter and choose between a faster or higher-quality algorithm with `highQuality`.

const turf = require('@turf/turf');
const polygon = turf.polygon([[[0, 0], [1, 1], [2, 2], [3, 3], [4, 4], [5, 5], [0, 0]]]);
const simplified = turf.simplify(polygon, {tolerance: 0.01, highQuality: false});
console.log(simplified);

Other packages similar to @turf/simplify

simplify-js

simplify-js is a high-performance JavaScript library for simplifying 2D geometries. It also uses the Ramer-Douglas-Peucker algorithm and is highly efficient for client-side applications. Compared to @turf/simplify, simplify-js is more focused on 2D geometries and does not support GeoJSON directly.

topojson-simplify

topojson-simplify is a module within the TopoJSON library that provides tools for simplifying TopoJSON objects. It uses a different approach compared to @turf/simplify, focusing on converting GeoJSON to TopoJSON and then simplifying the topology. This can result in more efficient storage and transmission of geographic data.

README

@turf/simplify

simplify

Takes a LineString or Polygon and returns a simplified version. Internally uses simplify-js to perform simplification.

Parameters

• feature (Feature<(LineString | Polygon | MultiLineString | MultiPolygon)> | FeatureCollection | GeometryCollection) feature to be simplified
• tolerance [number] simplification tolerance (optional, default 1)
• highQuality [boolean] whether or not to spend more time to create a higher-quality simplification with a different algorithm (optional, default false)

Examples

var feature = turf.polygon([[
  [-70.603637, -33.399918],
  [-70.614624, -33.395332],
  [-70.639343, -33.392466],
  [-70.659942, -33.394759],
  [-70.683975, -33.404504],
  [-70.697021, -33.419406],
  [-70.701141, -33.434306],
  [-70.700454, -33.446339],
  [-70.694274, -33.458369],
  [-70.682601, -33.465816],
  [-70.668869, -33.472117],
  [-70.646209, -33.473835],
  [-70.624923, -33.472117],
  [-70.609817, -33.468107],
  [-70.595397, -33.458369],
  [-70.587158, -33.442901],
  [-70.587158, -33.426283],
  [-70.590591, -33.414248],
  [-70.594711, -33.406224],
  [-70.603637, -33.399918]
]]);
var tolerance = 0.01;

var simplified = turf.simplify(feature, tolerance, false);

//addToMap
var addToMap = [feature, simplified]

Returns (Feature<(LineString | Polygon | MultiLineString | MultiPolygon)> | FeatureCollection | GeometryCollection) a simplified 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.

Installation

Install this module individually:

$ npm install @turf/simplify

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

$ npm install @turf/turf

Changelog

4.6.0

🚀 New Modules

• @turf/clean-coords Removes redundant coordinates from any GeoJSON Geometry. (PR https://github.com/Turfjs/turf/pull/875 - Author @stebogit)
• @turf/interpolate Takes a set of points and estimates their 'property' values on a grid using the Inverse Distance Weighting (IDW) method.. (PR https://github.com/Turfjs/turf/pull/832 - Author @stebogit)
• @turf/clusters-dbscan Takes a set of Points and partition them into clusters according to DBSCAN's data clustering algorithm. (PR https://github.com/Turfjs/turf/pull/812 and https://github.com/Turfjs/turf/pull/851 - Author @DenisCarriere)

  special mention to this incredibly instructive and fun interactive map by @DenisCarriere 😎👏

• @turf/clusters Provides getCluster, clusterEach, and clusterReduce functions. (PR https://github.com/Turfjs/turf/pull/847 - Author @DenisCarriere)
• @turf/boolean-point-on-line Returns true if a point is on a line. Accepts a optional parameter to ignore the start and end vertices of the linestring. (PR https://github.com/Turfjs/turf/pull/858 - Author @rowanwins)
• @turf/boolean-overlap Takes two features and returns true or false whether or not they overlap, i.e. whether any pair of edges on the two polygons intersect. If there are any edge intersections, the polygons overlap. (PR https://github.com/Turfjs/turf/pull/856 and https://github.com/Turfjs/turf/pull/868 - Author @stebogit @tcql)
• @turf/boolean-equal Determine whether two geometries of the same type have identical X,Y coordinate values. (PR https://github.com/Turfjs/turf/pull/869 - Author @stebogit @tcql)

🏅 New Features/Enhancements

• Sets centered param default to true in @turf/point-grid (PR https://github.com/Turfjs/turf/pull/836 - Contributor @stebogit)
• Adds MultiLineString support for @turf/point-on-line (PR https://github.com/Turfjs/turf/pull/838 - Contributor @stebogit)
• Renames @turf/clusters => @turf/clusters-kmeans, plus adds deprecated warning message to @turf/clusters@4.5.2 (See Issue https://github.com/Turfjs/turf/issues/845)
• Changes output type of @turf/clusters-kmeans (See Issue https://github.com/Turfjs/turf/issues/850 - Contributor @DenisCarriere)
• Adds segmentEach and segmentReduce functions to @turf/meta (See Issue https://github.com/Turfjs/turf/issues/850 - Contributor @DenisCarriere)
• Adds tests and linting on JSDoc in TurfJS core from turf-www; see Issue https://github.com/Turfjs/turf/issues/859 (PR https://github.com/Turfjs/turf/issues/857 + https://github.com/Turfjs/turf/issues/864 + https://github.com/Turfjs/turf/issues/870 - Contributor @DenisCarriere @stebogit)
• Introduces null Geometry support across TurfJS modules (See Issue https://github.com/Turfjs/turf/issues/853) (PR https://github.com/Turfjs/turf/issues/866 - Contributor @DenisCarriere)
• Includes feature(Sub)Index in coordEach/coordReduce (@turf/meta) 🎉 (PR https://github.com/Turfjs/turf/issues/872 - Contributor @DenisCarriere)
• Adds bbox and id params plus geometry method to @turf/helpers (PR https://github.com/Turfjs/turf/issues/877 - Contributor @DenisCarriere)

🐛 Bug Fixes

• Applies @turf/truncate to @turf/line-split splitter input to avoid approximation errors. Fixed #852 (PR https://github.com/Turfjs/turf/pull/855)
• Fixes @turf-mask error (See Issue https://github.com/Turfjs/turf/issues/837) (PR https://github.com/Turfjs/turf/pull/865 - Contributor @thiagoxvo)
• Fixes create-new-module script error on LICENSE file creation (See Issue https://github.com/Turfjs/turf/issues/861) (commit df6986e)
• Fixes @turf/isobands error on commonProperties (See Issue https://github.com/Turfjs/turf/issues/831) (commit 1663f07)