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Mapping buildings by construction year (BAG)

Source: vignettes/articles/bag-buildings.Rmd
bag-buildings.Rmd

The BAG (Basisregistratie Adressen en Gebouwen) holds every building in the Netherlands, with attributes such as the year it was built. It is served over the OGC API Features service, so pdok_read() reads it like any other layer. This article maps the buildings of one neighborhood, colored by construction year.

library(pdokr)
library(tmap)
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union

Choose an area

We use the administrative boundaries to select the Stadsdriehoek, the historic center of Rotterdam.

gemeenten <- pdok_read(
  "cbs/gebiedsindelingen", "gemeente_gegeneraliseerd", datetime = 2025
)
rotterdam <- filter(gemeenten, statnaam == "Rotterdam")

buurten <- pdok_read(
  "cbs/gebiedsindelingen", "buurt_gegeneraliseerd", datetime = 2025,
  filter_by = rotterdam, predicate = "within"
)
stadsdriehoek <- filter(buurten, statnaam == "Stadsdriehoek")

Load every building in it

The kadaster/bag dataset has a pand (building) layer. We filter it to the neighborhood; pdok_read() pre-filters at the server and clips to the exact shape.

buildings <- pdok_read("kadaster/bag", "pand", filter_by = stadsdriehoek)
#> ⠙ Downloading PDOK features: 363 fetched
#> ⠹ Downloading PDOK features: 808 fetched
#> ⠹ Downloading PDOK features: 1022 fetched
nrow(buildings)
#> [1] 1022

BAG records an unknown construction year as 9999; we set those to NA.

buildings <- mutate(buildings, bouwjaar = na_if(bouwjaar, 9999))
range(buildings$bouwjaar, na.rm = TRUE)
#> [1] 1609 2026

Map by construction year

Rotterdam’s historic center was largely destroyed in the May 1940 bombing and rebuilt afterwards. To make that dividing line jump out, we color the buildings that pre-date the bombing (before 1940) in cool blues and the post-war rebuild in warm tones — the surviving pre-war buildings stand out against a sea of reconstruction.

tmap_mode("plot")
#> ℹ tmap modes "plot" - "view"
#> ℹ toggle with `tmap::ttm()`

era_scale <- tm_scale_intervals(
  breaks = c(1600, 1900, 1940, 1960, 1980, 2000, 2026),
  values = c("#1f78b4", "#a6cee3", "#ffffb2", "#fecc5c", "#fd8d3c", "#e31a1c"),
  # Years are not thousands: drop the "." group separator (1.900 -> 1900).
  label.format = tm_label_format(big.mark = "")
)

tm_basemap(pdok_basemap("grijs")) +
  tm_shape(buildings) +
  tm_polygons(fill = "bouwjaar", fill.scale = era_scale, col = NULL) +
  tm_title("Buildings in Rotterdam's Stadsdriehoek, by construction year") +
  tm_credits("Kaartgegevens © Kadaster")
#> [plot mode] fit legend/component: Some legend items or map compoments do not
#> fit well, and are therefore rescaled.
#> ℹ Set the tmap option `component.autoscale = FALSE` to disable rescaling.

The same map interactively — zoom in and click a building:

tmap_mode("view")
#> ℹ tmap modes "plot" - "view"

tm_basemap(pdok_basemap("grijs")) +
  tm_shape(buildings) +
  tm_polygons(fill = "bouwjaar", fill.scale = era_scale, col = NULL,
              id = "identificatie",
              popup = tm_popup(vars = c("Built" = "bouwjaar"),
                               format = tm_label_format(big.mark = ""))) +
  tm_credits("Kaartgegevens © Kadaster")

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