Styling polygons of postcode zones that contain a point (address)

Question

I created a Map with Geocoded Addresses from the UK. The Basis for the map is a UK districts shapefile, this constitutes my main layer. After geocoding (via .csv) 3 Addresses I have a new layer with the three Address-Points.

The goal is now to create a Buffer around the Address Point that spans or fills out the entire area of the postcode to which that Address belongs. How can I implement this?

In the picture I included an example with a normal Buffer (just a circle with radius = x) the goal would be to fill the whole postal area with the Buffer.

Answer 1

You do not mention what software you are using but the workflow is the same for ArcGIS, ArcGIS Pro, or QGIS:

1. Create Voronoi polygons around your three points at an extent greater than the postcode polygon. For QGIS see Voronoi Polygons in Processing tools under Vector Geometry. For ArcGIS see ArcToolbox - Analysis Tools - Create Thiessen Polygons (advanced license only).
2. Clip the resulting Voronoi polygons with your postcode polygon. In QGIS try Vector Overlay - Clip, for ESRI try ArcToolbox - Analysis Tools - Extract - Clip.

Answer 2

If you are interested in filling the polygon would it not be more convenient to select the polygon based on the point location (Vector - Research Tools - Select by Location) and then saving these into a new polygon layer?

If you use this approach you would have to modify the polygon's attributes to reflect those of the point.

Answer 3

Be aware about terminology: what you ask about is not a "buffer", but to apply a style to a polygon layer based on spatial relationship from another layer: highlight the polygon that contain points. Easiest to achieve this is to use Geometry generator to add an additional symbol to the point layer: the polygon that the point is within.

To do so, on the point layer, add a new symbol layer of type Geometry generator and add this expression (replace polygon with the name of your postcode layer):

overlay_within('polygon',$geometry)[0]

All countries that contain a red point are styled in blue filled style: