@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
• options Object Optional parameters (optional, default {})
  • options.zProperty string the property name in points from which z-values will be pulled (optional, default 'elevation')
  • options.commonProperties Object GeoJSON properties passed to ALL isolines (optional, default {})
  • options.breaksProperties 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 pointGrid = turf.pointGrid(extent, cellWidth, {units: 'miles'});

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 lines = turf.isolines(pointGrid, breaks, {zProperty: 'temperature'});

//addToMap
var addToMap = [lines];

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

6.4.0

🏅 New Features/Enhancements

• @turf/boolean-point-on-line Added an epislon option to help in floating point comparison. (PR https://github.com/Turfjs/turf/pull/2051 - Author @okcoker)

🐛 Bug Fixes

• @turf/line-slice-along Fixed a bug where the offset distance equal to the length of the line (PR https://github.com/Turfjs/turf/pull/2030 - Author @EricPKerr)

• @turf/helpers Fixed the conversion ratio for converting meters to yards and vice-versa (PR https://github.com/Turfjs/turf/pull/2046 - Author @anotherhale)

• @turf/center-median Fixed a missing TS type import (PR https://github.com/Turfjs/turf/pull/2044 - Author @Seairth)

• `@turf/bezier-spline Fix a bug ensuring the spline result reaches the end of the input (PR https://github.com/Turfjs/turf/pull/2090 - Author @the-nemz)

📖 Documentation

• @turf/transform-rotate and @turf/ellipse) Improve documentation for angle parameter (PR https://github.com/Turfjs/turf/pull/2016 - Author @pasieronen)

• @turf/line-chunk Fix an invalid anchor (PR https://github.com/Turfjs/turf/pull/2071 - Author @GraxMonzo)

• @turf/distance Enhance distance doco so supported inputs are clearer (PR https://github.com/Turfjs/turf/pull/2032 - Author @rowanwins)

🔔 Misc

• @turf/concave Replace deprecated topojson dependency (PR https://github.com/Turfjs/turf/pull/2037 - Author @elliots)

• Work towards enabling TS Strict Mode (PR https://github.com/Turfjs/turf/pull/2053 - Author @mfedderly)