Postal code

The postcode areas are generated by so-called closest interpolation. The areas created by the interpolation called Thiessen polygons (Voronoi diagrams). Polygons with the same postal code have then been merged into larger areas. Basic data for the polygons comes from the city’s address point data. In the Postcode map there are a few smaller “polygon eyes” enclosed in larger areas. At the interpolation, single points create small islands outside the main area of the Postcode area. This means that there may be more than one polygon per postcode. The created areas are well aligned with the postal code areas provided by Postcode Service for a fee.