@turf/isolines

What is @turf/isolines?

@turf/isolines is a module within the Turf.js library that allows you to generate isolines (contour lines) from a grid of points with z-values. This is useful for visualizing elevation, temperature, or other continuous data over a geographic area.

What are @turf/isolines's main functionalities?

Generate Isolines

This feature allows you to generate isolines from a grid of points with z-values. The code sample demonstrates creating a grid of points, assigning random z-values, and generating isolines based on specified breaks.

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

// Create a grid of points with z-values
const points = turf.pointGrid([-95, 30, -85, 40], 100, { units: 'miles' });
points.features.forEach((point, i) => {
  point.properties.z = Math.random() * 10;
});

// Generate isolines
const breaks = [0, 2, 4, 6, 8, 10];
const isolines = turf.isolines(points, breaks, { zProperty: 'z' });

console.log(JSON.stringify(isolines));

Other packages similar to @turf/isolines

d3-contour

d3-contour is a module in the D3.js library that provides tools for generating contour plots. It is similar to @turf/isolines in that it can generate contour lines from a set of data points. However, d3-contour is more focused on data visualization and is part of the broader D3.js ecosystem, which is widely used for creating complex and interactive visualizations.

marching-squares

marching-squares is a JavaScript library for generating contour lines using the Marching Squares algorithm. It is similar to @turf/isolines in that it can generate contour lines from a grid of data points. However, marching-squares is a more specialized library focused solely on the contour generation algorithm, whereas @turf/isolines is part of the larger Turf.js library for geospatial analysis.

README

@turf/isolines

isolines

Takes a grid FeatureCollection of Point features with z-values and an array of value breaks and generates isolines.

Parameters

• pointGrid FeatureCollection<Point> input points
• breaks Array<number> values of zProperty where to draw isolines
• zProperty [string] the property name in points from which z-values will be pulled (optional, default 'elevation')
• propertiesToAllIsolines [Object] GeoJSON properties passed to ALL isolines (optional, default {})
• propertiesPerIsoline [Array<Object>] GeoJSON properties passed, in order, to the correspondent isoline; the breaks array will define the order in which the isolines are created (optional, default [])

Examples

// create a grid of points with random z-values in their properties
var extent = [0, 30, 20, 50];
var cellWidth = 100;
var units = 'miles';
var pointGrid = turf.pointGrid(extent, cellWidth, units);
for (var i = 0; i < pointGrid.features.length; i++) {
    pointGrid.features[i].properties.temperature = Math.random() * 10;
}
var breaks = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

var isolines = turf.isolines(pointGrid, breaks, 'temperature');

//addToMap
var addToMap = [isolines];

Returns FeatureCollection<MultiLineString> a FeatureCollection of MultiLineString features representing isolines

---

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/isolines

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)