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Spatial analysis

Buffer, dissolve, clip, overlay, spatial-join and more — the Analysis panel explained.

Analysis — under Tools in the left nav — runs spatial operations over a layer and drops the result back onto the map as a new layer you can style and export. It’s powered by DuckDB spatial, entirely in your browser.

How it works

  1. Pick a tool from the list. Tools are grouped (Shape & proximity, Convert geometry, Clean up, Overlay, Join & combine), and the search box finds one by name. Tools marked 2 layers take a second input layer.
  2. Pick the layer to operate on (and the second layer, if the tool needs one).
  3. If you have a selection, tick Selected features only to limit the operation to it.
  4. Set any parameters, then Run. The result is added as a new layer named after the source and operation, and the map zooms to it. The back arrow returns to the tool list.

Single-layer operations

Buffer and dissolve from the Analysis panel.
  • Buffer — grow features by a distance in metres, with cap (round/flat/square), join (round/mitre/bevel) and segments (arc smoothness) options.
  • Centroids / point on surface — reduce each feature to a point, either its true centroid or a point on surface (guaranteed inside the shape).
  • Convex hull / Concave hull — the tightest enclosing polygon; concave takes a tightness (0–1).
  • Simplify — reduce vertices to a tolerance in degrees, metres or pixels.
  • Extract vertices, Boundary (polygons → lines), Bounding boxes, Explode (multipart → singlepart), Make valid (repair geometry).
  • Dissolve (union) — merge features, optionally grouped by a field, into multipart or singlepart output.

Two-layer operations

  • Clip (keep inside) / Erase (remove inside) — cut one layer by another.
  • Intersect / Union / Symmetric difference — combine two layers; intersect and union carry attributes from both.
  • Join attributes by location — copy attributes from a second layer onto features by spatial relationship (intersects, contains, within, nearest), keeping the first match or all matches, with an optional field prefix.
  • Count features in polygon — count points (or features) falling inside each polygon, written to a named count field.
  • Append / merge layers — stack two layers’ features, each keeping its own attributes.

For anything not listed here, the SQL console gives you the full spatial function set.

Next steps