turf.tin

What is turf.tin?

turf.tin computes a Delaunay-based Triangulated Irregular Network (TIN) over a FeatureCollection<Point>. It returns a FeatureCollection<Polygon> where every polygon is a triangle, and each triangle carries the vertex z-values under properties a, b, c.

turf.tin(points, z?) → FeatureCollection<Polygon>

Parameters:

• points — input point collection
• z — optional property name on each point whose value becomes the triangle's a/b/c

When would you use turf.tin?

Use turf.tin when you have scattered 3D data (elevation, temperature, rainfall) and you want a lightweight surface model that you can interpolate inside (via turf.planepoint), render as shaded triangles, or pass to a downstream client-side renderer.

TINs are well suited to data that is naturally irregular — survey points, weather stations, sensor readings. They preserve the original points exactly (every input becomes a triangle corner), unlike interpolation onto a regular grid.

1const triangles = turf.tin(stations, 'elevation');
2map.getSource('tin').setData(triangles);

FAQs

How do I install Turf.js to use this function?

Install npm install @turf/tin and import import { tin } from '@turf/tin'. The umbrella bundle exposes turf.tin.

What happens if I have duplicate input points?

Duplicate coordinates can cause the triangulation to fail or produce degenerate triangles. Deduplicate your input before calling — keep one representative point per location and, if necessary, average the z-values.

How do I read the z-value at a non-vertex location?

Find the triangle containing your query point with turf.booleanPointInPolygon, then call turf.planepoint(point, triangle) to barycentrically interpolate across the triangle's plane.

When should I use a grid-based interpolation instead?

Use turf.interpolate when you need a raster-like surface for contouring (turf.isolines, turf.isobands) or equal-resolution analysis. Use turf.tin when you want to preserve original sample locations and keep triangular polygons as analysis units.