Today a plain IDW alg. implemented in JS. Tomorrow a Turf.js package? Maybe?
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tests refactored index code & add tests Apr 21, 2016
.gitignore update .gitignore Apr 21, 2016 update Aug 16, 2016
celebration.gif success! module accepted on TurfJs. Update Aug 16, 2016
index.js fixed valueField bug Apr 22, 2016
package.json refactored index code & add tests Apr 21, 2016
test.js cleaned blank lines Apr 21, 2016


Today a plain IDW alg. implemented in JS. Tomorrow a Turf.js package? Maybe?


The module has been accepted and is now officially part of TurfJs! You can find it on Turf's repo or as a stand-alone module on npm thanks to @tmcw and @morganherlocker.

Obligatory happy celebratory gif:


IDW(controlPoints, valueField, b, cellWidth, units)

Takes a set of known sampled points, a property containing data value, an exponent parameter, a cell depth, a unit of measurement and returns a set of square polygons in a grid with an IDW value for each cell.

Based on the Inverse Distance Weighting interpolation algorithm as covered in the following (among other) resources: [1], [2].


parameter type description
controlPoints FeatureCollection Sampled points with known value
valueField String GeoJSON field containing the data value to interpolate on
b Number Exponent regulating the distance weighting
cellWidth Number The distance across each cell
units String Used in calculating cellWidth ('miles' or 'kilometers')


// load IDW
var IDW = require('./index.js')

// load a sample of test points
var fs = require('fs');
var controlPoints = JSON.parse(fs.readFileSync('./data/data.geojson'));

// produce an interpolated surface
var IDWSurface = IDW(controlPoints,'value', 0.5, 0.1,'kilometers');

Installation & Use

Requires nodejs.

Git clone this repo, then require it


$ npm test


[1] O’Sullivan, D., & Unwin, D. (2010). Geographic Information Analysis (2nd Edition). 432pp. Hoboken, New Jersey (USA): John Wiley & Sons, Inc.

[2] Xiao, N. (2016). GIS Algorithms, 336pp. SAGE Publications Ltd.