Clip

Keep only the parts of input features that fall inside a clip polygon. Cookie-cutter style.

basic

A clip step trims each input feature to the parts that fall inside a clip polygon. Features entirely outside drop out; features that cross the polygon boundary are cut.

This is the spatial "intersect with this shape" operation. Cookie-cutter: hand it a parcel layer and a city boundary, get back the parcels inside the city, with parcels on the edge trimmed at the boundary.

Inputs

  • Source layer. Any geometry type.
  • Clip polygon. One of: - A Geo boundary item (the most common case). - A single feature picked from another polygon layer. - A static polygon defined inline (paste GeoJSON).

Output

A new layer with the source's schema. Each row's geometry is ST_Intersection(source.geometry, clip). Rows whose geometry doesn't intersect the clip drop out entirely; rows whose geometry is entirely inside come through unchanged.

How to use it on its own

  1. New-item wizard → Derived layer.
  2. Pick a Source.
  3. Add a Clip step.
  4. Pick the Clip polygon.
  5. Save.

Example

You have a state-wide road network. You want just the segments inside one county. Add a Clip step with the county's geo boundary as the clip polygon. Output is the road segments trimmed to the county line.

Clip vs. spatial join with "within"

  • Clip trims geometry; the output's geometry is the intersected piece. Roads sticking out beyond the county line are cut at the line.
  • Spatial join with within keeps the whole input geometry if any part is inside the join polygon. Same roads, kept whole if they're "in" the county at all.

Pick clip when the geometry needs to stay within the polygon; pick spatial-join-with-within when you want intact features plus an attribute identifying which polygon they're in.

Notes

  • Clip a polygon by a polygon produces a polygon. Common case for "limit this layer to the project area".
  • Clip a line by a polygon produces line segments at the boundary cut.
  • Clip a point by a polygon is equivalent to a filter "points inside this polygon"; same result, both work.
  • The clip polygon's coordinate system is reconciled automatically.