Maps and addresses: PDOK and the Kadaster

Where the map, the addresses and the postcodes on Sumish come from, and why the map runs through our own server and passes nothing on about you.

4 min readPublished October 11, 2026, checked October 11, 2026

On Sumish you see maps, addresses and postcodes. They come from official sources: from the Kadaster (the Dutch land registry and mapping agency), via PDOK, and from Statistics Netherlands (CBS). This page explains which sources these are, how often we update them and why the map runs through our own server.

The map

The base of the map is the Kadaster's BRT-Achtergrondkaart (topographic background map; page in Dutch), in shades of gray. PDOK (Publieke Dienstverlening Op de Kaart, the Dutch public geodata service) makes it available free of charge. The Kadaster updates the map five times a year.

Through our own server. Your browser asks sumish.eu for the map, never PDOK directly. Our server fetches the map tiles from PDOK and stores them. Nothing about you goes to PDOK, not even your IP address. We do not use maps from Google or other parties.
Only after a click. The map loads only when you open it.
Nothing recorded. We do not keep track of which part of the map you view.
Checked every month. We check a stored map tile with PDOK again after 30 days. A new version of the map is therefore in place within about a month.
The Netherlands only. Outside the Netherlands the map is blank. The tools only search in the Netherlands.
A route only opens when you click it, in OpenStreetMap or in the map app of your device. Only that place is then sent to that service.

The map carries the credit Map data © Kadaster, with the license CC BY 4.0. Area boundaries also carry Source: CBS, Kadaster, and gasoline stations © OpenStreetMap contributors.

Addresses: the BAG

The Kadaster's Basisregistratie Adressen en Gebouwen (BAG, the Dutch register of addresses and buildings; page in Dutch) contains all addresses in the Netherlands. Dutch Postcode Finder uses it, as do the suggestions in the search fields of, among others, Find Parking in the Netherlands and Distance Between Places in the Netherlands.

Every month we fetch the complete BAG file via PDOK. We keep only what we need: per postcode the street, the town and the house numbers, and per town the municipality (gemeente). This is how you also find a village that is not a municipality of its own.
We then discard the file. So we do not keep a copy of the whole BAG.
Only main addresses are included. Addresses that have been withdrawn, entered by mistake or never built are left out.
An address that is brand new or has just changed may still be missing. A house letter or addition sometimes has a different postcode.

The BAG is free to use (CC0). We still credit it as Source: Kadaster (BAG).

Postcodes with figures

CBS publishes figures per postcode (page in Dutch): for every six-character postcode (such as 3511 AB) and every four-digit one (3511). Each postcode has an area on the map. This is how Dutch Neighborhood Statistics shows the homes, the WOZ value (the official property value) and the owner-occupied and rented homes of your postcode.

CBS rounds the figures and keeps small numbers secret. For a small postcode, many figures are therefore not known.
The center of a postcode is an approximation, not the location of an address.
CBS makes the files available free of charge. The rights stay with CBS, and the figures carry Source: CBS.

Distance: as the crow flies

Distance Between Places in the Netherlands and the search tools for parking, charging and refuelling measure from the center of a postcode or town, in a straight line. That is as the crow flies, not the route. By road it is usually a quarter to a third further.

From address to neighborhood

Which neighborhood, district (wijk) and municipality an address belongs to is derived by CBS from the BAG. We use that file in the tools with neighborhood figures. You can read more about it in CBS figures on neighborhoods and municipalities.

Your search

An address, postcode or place you type is used only for that search. We do not store it, and it does not end up in our statistics or log files. Do you want to search from where you are? Then read Sharing your location.

How we update and monitor the data is explained in How we keep everything up to date.

The Sumish editorial team