Working with imagery

Diego Hernangómez

mapSpain provides a powerful interface for working with imagery. It can download static files as .png or .jpeg (depending on the Web Map Service) and use them alongside your shapefiles.

mapSpain also provides a plugin for the R Leaflet package, which allows adding multiple basemaps to interactive maps.

The services are implemented via the Leaflet plugin leaflet-providersESP. You can view each provider option at that link.

Static tiles

An example showing how to include multiple tiles to create a static map. We focus on layers provided by La Rioja’s Infraestructura de Datos Espaciales (IDERioja).

• When working with imagery, set moveCAN = FALSE; otherwise images for the Canary Islands may be inaccurate.

library(mapSpain)
library(sf)
library(ggplot2)
library(tidyterra)

# Logroño
lgn_borders <- esp_get_munic_siane(munic = "Logroño")

# Convert to Mercator (EPSG:3857) as a general advice when working with tiles
lgn_borders <- st_transform(lgn_borders, 3857)

tile_lgn <- esp_get_tiles(lgn_borders, "IDErioja", bbox_expand = 0.5)

ggplot(lgn_borders) +
  geom_spatraster_rgb(data = tile_lgn) +
  geom_sf(fill = NA, linewidth = 2, color = "blue")

Figure 1: Map of the limits of city of Logroño using a tile as a basemap

Alpha value on tiles

Some tiles can be loaded with or without an alpha (transparency) value, which controls layer transparency:

galicia <- esp_get_ccaa("Galicia", epsg = 3857)

# Example without transparency
basemap <- esp_get_tiles(
  galicia,
  "IDErioja.Claro",
  zoommin = 1,
  crop = TRUE,
  bbox_expand = 0
)
tile_opaque <- esp_get_tiles(
  galicia,
  "CaminoDeSantiago",
  verbose = TRUE,
  transparent = FALSE,
  crop = TRUE,
  bbox_expand = 0
)

ggplot() +
  geom_spatraster_rgb(data = basemap) +
  geom_spatraster_rgb(data = tile_opaque) +
  theme_void()

Figure 2: Map of the Way of St. James in Galicia

Now let’s check the same code using the transparent = TRUE option:

# Example with transparency
tile_alpha <- esp_get_tiles(
  galicia,
  "CaminoDeSantiago",
  transparent = TRUE,
  crop = TRUE,
  bbox_expand = 0
)

# Same code than above for plotting
ggplot() +
  geom_spatraster_rgb(data = basemap) +
  geom_spatraster_rgb(data = tile_alpha) +
  theme_void()

Figure 3: Example on how to use alpha value for combining different types of basemaps.

Now the two tiles overlap with the desired transparency.

Masking tiles

Another useful feature is the ability to mask tiles, allowing more advanced maps to be plotted:

rioja <- esp_get_prov("La Rioja", epsg = 3857)

basemap <- esp_get_tiles(rioja, "PNOA", bbox_expand = 0.1, zoommin = 1)

masked <- esp_get_tiles(rioja, "IDErioja", mask = TRUE, zoommin = 1)

ggplot() +
  geom_spatraster_rgb(data = basemap, maxcell = 10e6) +
  geom_spatraster_rgb(data = masked, maxcell = 10e6)

Figure 4: Example of combining types of tiles by masking to a shapefile.

Custom providers

You can use esp_get_tiles() to get tiles of any other provider, for example OpenStreetMap:

osm_spec <- list(
  id = "OSM",
  q = "https://tile.openstreetmap.org/{z}/{x}/{y}.png"
)

madrid_city <- esp_get_munic_siane(munic = "^Madrid$", epsg = 3857)
madrid_osm <- esp_get_tiles(madrid_city, type = osm_spec, zoommin = 1)

ggplot() +
  geom_spatraster_rgb(data = madrid_osm) +
  geom_sf(data = madrid_city, fill = NA)

Figure 5: Example of base map using OpenStreetMap

Another example using a provider that needs an API Key (ThunderForest):

# Skip if not API KEY
apikey <- Sys.getenv("THUNDERFOREST_API_KEY", "")
if (apikey != "") {
  thunder_spec <- list(
    id = "ThunderForest",
    q = paste0(
      "https://tile.thunderforest.com/transport/{z}/{x}/{y}.png?apikey=",
      apikey
    )
  )
  madrid_thunder <- esp_get_tiles(madrid_city, type = thunder_spec, zoommin = 1)

  ggplot() +
    geom_spatraster_rgb(data = madrid_thunder) +
    geom_sf(data = madrid_city, fill = NA)
}

Example of base map using ThunderForest

Dynamic maps with Leaflet

mapSpain provides a plugin for the Leaflet package. Below are some quick examples:

Earthquakes in Tenerife (last year)

library(leaflet)

tenerife_leaf <- esp_get_nuts(
  region = "Tenerife",
  epsg = 4326,
  moveCAN = FALSE
)

bbox <- as.double(round(st_bbox(tenerife_leaf) + c(-1, -1, 1, 1), 2))

# Start leaflet
m <- leaflet(
  tenerife_leaf,
  elementId = "tenerife-earthquakes",
  width = "100%",
  height = "60vh",
  options = leafletOptions(minZoom = 9, maxZoom = 18)
)

# Add layers
m <- m |>
  addProviderEspTiles("IDErioja.Relieve") |>
  addPolygons(color = NA, fillColor = "red", group = "Polygon") |>
  addProviderEspTiles("Geofisica.Terremotos365dias", group = "Earthquakes")

# Add additional options
m |>
  addLayersControl(
    overlayGroups = c("Polygon", "Earthquakes"),
    options = layersControlOptions(collapsed = FALSE)
  ) |>
  setMaxBounds(bbox[1], bbox[2], bbox[3], bbox[4])

Population density in Spain

A map showing the population density of Spain as of 2019:

library(leaflet)
library(dplyr)
munic <- esp_get_munic_siane(
  year = "2025-01-01",
  epsg = 4326,
  moveCAN = FALSE,
  rawcols = TRUE
) |>
  # Get area in km2 from siane munic
  # Already on the shapefile
  mutate(area_km2 = st_area_sh * 10000)

# Get population
pop <- mapSpain::pobmun25 |>
  select(-name)

# Paste
munic_pop <- munic |>
  left_join(pop) |>
  mutate(
    dens = pob25 / area_km2,
    dens_label = prettyNum(round(dens, 2), big.mark = ".", decimal.mark = ",")
  )

# Create leaflet
bins <- c(0, 10, 25, 100, 200, 500, 1000, 5000, 10000, Inf)

pal <- colorBin("inferno", domain = munic_pop$dens, bins = bins, reverse = TRUE)

labels <- sprintf(
  "<strong>%s</strong><br/><em>%s</em><br/>%s pers. / km<sup>2</sup>",
  munic_pop$rotulo,
  munic_pop$ine.prov.name,
  munic_pop$dens_label
) |>
  lapply(htmltools::HTML)

leaflet(elementId = "SpainDemo", width = "100%", height = "60vh") |>
  setView(lng = -3.684444, lat = 40.308611, zoom = 5) |>
  addProviderEspTiles("IDErioja") |>
  addPolygons(
    data = munic_pop,
    fillColor = ~ pal(dens),
    fillOpacity = 0.6,
    color = "#44444",
    weight = 0.5,
    smoothFactor = .1,
    opacity = 1,
    highlightOptions = highlightOptions(
      color = "white",
      weight = 1,
      bringToFront = TRUE
    ),
    popup = labels
  ) |>
  addLegend(
    pal = pal,
    values = bins,
    opacity = 0.7,
    title = paste0(
      "<small>Pop. Density km<sup>2</sup></small><br><small>",
      "(2025)</small>"
    ),
    position = "bottomright"
  )

Available providers

The esp_tiles_providers list contains metadata for the tile providers available to the functions above. It includes all arguments required to reproduce the API request. Below is the static URL for each provider: