R osmdata query returns object contaminated with results from an old query

November 29, 2021

I have made the following query using the osmdata package:

library(osmdata)
library(sf)

# Get map boundaries for UK:
bb <- getbb ('uk', format_out = 'polygon')

# Fetch data for selected boundaries from osmdata:
ukbasemap <- opq(bbox = bb) %>% # set boundary box
  add_osm_feature(key = 'admin_level', value = '4') %>% # add feature
  osmdata_sf () %>% # convert to sf object
  trim_osmdata (bb) # trim to edges of boundary (i.e. UK borders)

This returned the following warning, but otherwise created the sf object without apparent issue:
bb_poly has more than one polygon; the first will be selected.

I then tried to plot the data, but the below code produces a blank plot:

> sf::plot_sf(ukbasemap$osm_lines)
> sf::plot_sf(ukbasemap$osm_polygons)
> sf::plot_sf(ukbasemap$osm_multipolygons)
> sf::plot_sf(ukbasemap$osm_points)

When I inspected the sf object, I was surprised to see some place names from Central African Republic in it. I ran a query for CAR a few months ago, and the only thing I can think of is that I accidentally set some global options to refer to CAR data – but I don’t remember doing that. Here is a snippet of what the sf object looks like:

> ukbasemap$osm_points
Simple feature collection with 2 features and 23 fields
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: 20.54475 ymin: 5.768001 xmax: 20.67557 ymax: 6.311055
Geodetic CRS:  WGS 84
               osm_id    name   GNS.id alt_name capital created_by  ele ford is_in.continent
2222388003 2222388003   Ouaka     <NA>     <NA>    <NA>       <NA> <NA> <NA>            <NA>
4680378478 4680378478 Bambari -1339188     <NA>       4       <NA> <NA> <NA>            <NA>
           is_in.country name.de name.en   name.ko  name.ru name.sg  name.uk place
2222388003          <NA>    <NA>    <NA>      <NA> Ð£Ð°ÐºÐ°  WÃ¤kÃ¤ Ð£Ð°ÐºÐ° state
4680378478          <NA>    <NA>    <NA> ë°¤ë°”ë¦¬     <NA>    <NA>     <NA>  city
           population  ref source state_code wikidata wikipedia                  geometry
2222388003       <NA>   UK   <NA>         UK  Q848560  fr:Ouaka POINT (20.54475 6.311055)
4680378478      41356 <NA>    GNS       <NA>  Q805946      <NA> POINT (20.67557 5.768001)

"Ouaka" and "Bambari" are place names in Central African Republic.

Does anyone know what could be going on here and how can I fix it?

>Solution :

This is because your bounding box does not actually refer to the United Kingdom. It is the case because the default featuretype = "settlement" combines results from all intermediate levels below "country" and above "streets" (see here).

You can get the bounding box for a country by adding feature_type = "country".

bb <- getbb("uk", format_out = 'polygon', featuretype = "country")

You can check whether your bounding box is correct by mapping it like this.

library(leaflet)

bb <- getbb("uk", format_out = 'sf_polygon', featuretype = "country")

leaflet(bb$multipolygon) %>% 
  addProviderTiles("CartoDB.Positron") %>% 
  addPolygons()