Vector Analysis

This tutorial runs a small vector workflow: buffer a layer, overlay it with another, and export the result. It uses the Vector tools under Processing → Vector.

1. Load input data

Add at least one vector layer (see Adding Data). For an overlay you will need two layers, for example a set of points or lines and a polygon layer to clip against.

2. Buffer a layer

1. Open Processing → Vector → Buffer.
2. Set Input layer to your layer.
3. Set the Distance and Units (kilometers, meters, or miles).
4. Choose an Engine:
   • Client (Turf.js) runs in the browser with no setup.
   • Sidecar (GeoPandas) runs on the Python sidecar for projection-aware distances (desktop app).
5. Click Run. A buffered layer is added to the map.

!!! tip “Projection-aware distances” The client engine buffers in geographic coordinates. For accurate metric distances over large areas, use the GeoPandas sidecar engine, which reprojects before buffering.

3. Overlay two layers

With the buffer (or any polygon layer) and a second layer, run an overlay:

• Clip keeps the part of the input that falls inside the overlay, preserving the input’s attributes.
• Intersection keeps only the overlapping areas of two polygon layers.
• Difference removes the overlay’s area from the input.
• Union merges two polygon layers into one (attributes are not preserved, on either engine).
• Spatial join attaches a join layer’s attributes to each input feature based on a spatial relationship (intersects, within, or contains) — for example, tagging each point with the polygon that contains it. Works with any geometry type.
• Attribute join attaches a join table’s attributes to each input feature where a key field matches — no geometry involved (for example, joining census statistics to boundary polygons by a shared FIPS code). It is one-to-one (the first matching join row wins); pick the key field on each side, optionally list which fields to bring over, and choose an inner or left join.

Open the tool from Processing → Vector, pick the input and overlay layers, and Run.

4. Inspect and refine

Open the Attribute table on the result layer to check the output, and adjust its style so it stands out from the inputs.

5. Export the result

To save the output as a cloud-native file, use Processing → Conversion (for example Vector to GeoParquet or Vector to FlatGeobuf). See Cloud-Native Data. You can also export records from the Attribute table or the SQL Workspace.

Next steps

• Do the same kind of analysis in SQL with Spatial SQL.
• Move to raster analysis in Terrain Analysis.