Centroid

Replace each feature's geometry with a single point at its center.

basic

A centroid step replaces each feature's geometry with a single point at the feature's center. Attributes are kept; only the geometry changes from polygon (or line) to point.

Use when a downstream step or rendering wants point geometry: labeling at a single anchor, clustering, point-symbol rendering of a polygon layer, or input to a join that expects points.

Inputs

  • Source layer.
  • Centroid type: - Geometric centroid. The math centroid. For convex polygons, this is the visual center. For irregular shapes (a U-shaped polygon), it can fall outside the polygon. - Pole of inaccessibility. The point inside the polygon that's furthest from any edge. Always inside. Slower to compute but visually nicer for labels. - Bounding-box center. The center of the polygon's bbox. Cheap; useful only when the polygon is roughly rectangular.

Output

A new layer with point geometry. Attributes copied verbatim.

How to use it on its own

  1. New-item wizard → Derived layer.
  2. Pick a non-point Source.
  3. Add a Centroid step.
  4. Choose the centroid type.
  5. Save.

Example

You have a parcel polygon layer and want a "parcel centroids" point layer to use as the click target on a basemap-style map (polygons read as decoration, points as the interactive layer). Centroid step, type "Pole of inaccessibility" so the click point is reliably inside the parcel.

Notes

  • Centroid of a multipart geometry is one point: the centroid of the combined geometry. Not one per part.
  • Linestrings have centroids too. The midpoint along the line.
  • NULL geometry features produce NULL output points and drop from rendering.