@turf/idw

@turf/idw

idw

Takes a FeatureCollection of points with known value, a power parameter, a cell depth, a unit of measurement and returns a FeatureCollection of polygons in a square-grid with an interpolated value property "IDW" for each grid cell. It finds application when in need of creating a continuous surface (i.e. rainfall, temperature, chemical dispersion surface...) from a set of spatially scattered points.

Parameters

• controlPoints FeatureCollection<Point> Sampled points with known value
• valueField string GeoJSON field containing the known value to interpolate on
• weight number Exponent regulating the distance-decay weighting
• cellWidth number The distance across each cell
• units [string] used in calculating cellSize, can be degrees, radians, miles, or kilometers (optional, default kilometers)

Returns FeatureCollection<Polygon> grid A grid of polygons with a property field named as valueField

---

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/idw

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)