Placing register units on the map — Task
Implementation: Placing register units on the map (Recipe - QGIS).
Placing register units on the map is the Task of giving units from a register a location: a flat in BBR, a company in CVR, a person in a statistical extract. The unit itself has no coordinates. It has ids that point to other registers, and the location is found by following those ids from table to table. For a dwelling in BBR there are two routes: through the address register (DAR) to the address point at the entrance, or through BBR to the building’s point.
Used in examples: Share of rented dwellings in Copenhagen (Example), Dwelling size by construction period in Copenhagen (Example).
The example building, Eksempelgade 12–14, is made up. One BBR building has two entrances, each a DAR house number; every flat is a BBR unit with its own DAR address. Flats on the same staircase share one address point.
The joins
Every step is a join: a field holding an id in one table matches id_lokalId, the id of a row, in the next table.
| Step | From (field) | To (field) | What it gives |
|---|---|---|---|
| 1 | BBR_Enhed.adresseIdentificerer | DAR_Adresse.id_lokalId | the unit’s full address, with floor and door: adressebetegnelse |
| 2 | DAR_Adresse.husnummer | DAR_Husnummer.id_lokalId | the entrance, also called the access address (adgangsadresse): adgangsadressebetegnelse |
| 3 | DAR_Husnummer.adgangspunkt | DAR_Adressepunkt.id_lokalId | the entrance’s coordinates: position |
| Alternative | BBR_Enhed.bygning | BBR_Bygning.id_lokalId | the building’s coordinates byg404Koordinat, construction year, building use |
The old name for a house number is adgangsadresse (from DAWA and the old BBR), which is why the field is called adgangsadressebetegnelse.
Task Schema (tool-agnostic)
- Get each register’s table (Operator: extract to the area) — for Copenhagen the downloads for municipality 0101 where Datafordeleren offers them; DAR’s national tables filtered to the municipality.
- Select the units (Operator: selection by attribute) — e.g. standing dwellings.
- Choose the route (decision point) — address point or building point.
- Join step by step (Operator: join by key) — unit → address → house number → address point; or unit → building.
- Make the points (Operator: join onto the point layer, one point per unit).
- Count — units in, points out; list the units that found no address or no building.
Output: one point per unit, with the unit’s attributes and its address.
Epistemic Choices to record
- Address point or building point: the address point when the staircase matters (a long block on a corner can have entrances on two streets, 50 m or more apart, and in different statistical districts); the building point when one point per building is enough or when a unit has no address. It takes one join instead of three.
- Neither point is the unit: every flat on a staircase gets the same point. Floor and door are only in the address text.
- Units that do not match: in Copenhagen, 8,590 of 491,935 units have no DAR address, all of them historic, closed or registered in error; 1,672 units have no building point. Say how many were lost and why.
- Current or historical: the downloads exist as Current and with history; mixing them gives several versions of the same unit.
- Date: each register is extracted on its own date.