turf.transformScale

What is turf.transformScale?

turf.transformScale scales any GeoJSON Feature by a factor around an origin. Factor 2 doubles the size, 0.5 halves it, 1 returns unchanged. The operation is geodesic — each vertex is projected along its bearing from the origin at a scaled distance.

turf.transformScale(geojson, factor, options?) → Feature<Geometry>

Options include:

• origin — Point or corner string ('sw', 'nw', 'ne', 'se', 'center', 'centroid'); default 'centroid'
• mutate — boolean (default false); when true, mutates the input in place

When would you use turf.transformScale?

Use turf.transformScale to grow or shrink a shape around an anchor — scaling a geofence for a larger event area, creating nested radius polygons from a footprint, or resizing a drawn selection proportionally. Combined with turf.transformRotate and turf.transformTranslate it handles the full affine family.

In a Node.js build step, turf.transformScale can generate progressively smaller/larger variants of a template polygon for a scenario-analysis tool or for generating "hit zones" around a primary footprint.

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FAQs

What happens at factor = 0?

Every vertex collapses to the origin. Practically, this produces a degenerate feature — avoid or clamp to a small positive value.

What origin options are available?

A GeoJSON Point or a corner keyword: 'sw', 'nw', 'ne', 'se', 'center' (of bbox), or 'centroid' (of vertices). Default is 'centroid'.

How do I install just transformScale?

npm install @turf/transform-scale. Its dependencies include @turf/center, @turf/bbox, @turf/centroid, @turf/rhumb-bearing, @turf/rhumb-destination, and @turf/meta.

Is the scaling uniform in geographic distance?

Yes — turf.transformScale computes distances geodetically and scales each vertex by the requested factor along its rhumb bearing from the origin. This avoids the distortion you would get from scaling raw degrees.