@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 = {
  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "Polygon",
    "coordinates": [[
      [-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

4.4.0

🚀 New Modules

• @turf/line-offset Adds a new lineOffset module as per this issue. Basically takes an input line and returns a new line offset by the distance. (PR https://github.com/Turfjs/turf/pull/729 - Author @rowanwins)
• @turf/polygonize Polygonizes (Multi)LineString(s) into Polygons. Implementation of GEOSPolygonize function (geos::operation::polygonize::Polygonizer). (PR https://github.com/Turfjs/turf/pull/767 - Author @NickCis)
• @turf/transform-rotate Rotates any geojson Feature or Geometry of a specified angle, around its centroid or a given pivot point; all rotations follow the right-hand rule. (Issue https://github.com/Turfjs/turf/issues/747 - Author @stebogit)
• @turf/transform-translate Moves any geojson Feature or Geometry of a specified distance along a Rhumb Line on the provided direction angle. (Issue https://github.com/Turfjs/turf/issues/747 - Author @stebogit)
• @turf/transform-scale Scale a GeoJSON from a given point by a factor of scaling (ex: factor=2 would make the GeoJSON 200% larger). If a FeatureCollection is provided, the origin point will be calculated based on each individual Feature. (Issue https://github.com/Turfjs/turf/issues/747 - Author @stebogit)

🏅 New Features

• Support z-coordinate as input for @turf/turf-tin (PR https://github.com/Turfjs/turf/pull/772)
• Adds properties parameter to @turf/centroid and @turf/center (PR https://github.com/Turfjs/turf/pull/769)
• Include Yarn.lock for all modules & Lerna uses Yarn (Issue https://github.com/Turfjs/turf/issues/704, https://github.com/Turfjs/turf/issues/765, PR https://github.com/Turfjs/turf/pull/766)
• Use Tap at root which enables code coverage reports (Issue https://github.com/Turfjs/turf/issues/328 & PR https://github.com/Turfjs/turf/pull/762)
• Support z-coordinate as input for @turf/pointplane (PR https://github.com/Turfjs/turf/pull/754)
• Add core tests - file management & package.json rules (PR https://github.com/Turfjs/turf/pull/749 & https://github.com/Turfjs/turf/pull/756)

🐛 Bug Fixes

• Website http://turfjs.org is back up and running (Issue https://github.com/Turfjs/turf/issues/777)
• @turf/rhumb-destination issue at 180th meridian (Issue https://github.com/Turfjs/turf/issues/770 & PR https://github.com/Turfjs/turf/pull/771)
• Getting too large numbers for Longitude (Issue https://github.com/Turfjs/turf/issues/758 & PR https://github.com/Turfjs/turf/pull/763)
• Throw error if FeatureCollection not array #751 (PR https://github.com/Turfjs/turf/pull/760)
• Change default param coordinates to 3 @turf/truncate (PR https://github.com/Turfjs/turf/pull/757)
• along returns a point that is not found by @turf/point-on-line (Issue https://github.com/Turfjs/turf/issues/691)
• Fix location of intersect point for @turf/point-on-line. (PR https://github.com/Turfjs/turf/pull/750)
• Handle empty geometries as undefined @turf/buffer (PR https://github.com/Turfjs/turf/pull/746)