Combining points and polygons - in package or an add-on package?

[Robinlovelace]

Sometimes it's useful to combine polygons and points. For example, supermarkets are represented as both points and polygons. I've written a test function that combines them: https://github.com/Nowosad/SIGR2021/blob/master/workshop1/osm_combine.R

Think this is worth packaging but, in the interests of keeping osmextract small and maintainable would suggest putting this general osm processing functionality in separate package, e.g. called osmextras.

Thoughts?

[agila5]

Hi @Robinlovelace! Are you sure that the code written in that function is appropriate for osmextract? I think that is more relevant for osmdata since, AFAIK, the "duplicated" points are "removed" when building the POLYGON objects.

For example:

# package
library(osmextract)
#> Data (c) OpenStreetMap contributors, ODbL 1.0. https://www.openstreetmap.org/copyright.
#> Check the package website, https://docs.ropensci.org/osmextract/, for more details.
library(sf)
#> Linking to GEOS 3.9.0, GDAL 3.2.1, PROJ 7.2.1

# get supermarks
supermarkets_points <- oe_get(
  "Isle of Wight", 
  layer = "points", 
  extra_tags = "shop", 
  query = "SELECT * FROM points WHERE shop = 'supermarket'"
)
#> The input place was matched with: Isle of Wight
#> The chosen file was already detected in the download directory. Skip downloading.
#> The corresponding gpkg file was already detected. Skip vectortranslate operations.
#> Reading layer `points' from data source 
#>   `C:\Users\Utente\Documents\osm-data\geofabrik_isle-of-wight-latest.gpkg' 
#>   using driver `GPKG'
#> Simple feature collection with 7 features and 11 fields
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: -1.29727 ymin: 50.58849 xmax: -1.145604 ymax: 50.76113
#> Geodetic CRS:  WGS 84
supermarkets_polygons <- oe_get(
  "Isle of Wight", 
  layer = "multipolygons", 
  extra_tags = "multipolygons", 
  query = "SELECT * FROM multipolygons WHERE shop = 'supermarket'"
)
#> The input place was matched with: Isle of Wight
#> The chosen file was already detected in the download directory. Skip downloading.
#> The corresponding gpkg file was already detected. Skip vectortranslate operations.
#> Reading layer `multipolygons' from data source 
#>   `C:\Users\Utente\Documents\osm-data\geofabrik_isle-of-wight-latest.gpkg' 
#>   using driver `GPKG'
#> Simple feature collection with 18 features and 26 fields
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -1.515673 ymin: 50.63308 xmax: -1.142295 ymax: 50.76222
#> Geodetic CRS:  WGS 84

# intersection
lengths(st_intersects(supermarkets_points, supermarkets_polygons))
#> [1] 0 0 0 0 0 0 0

^{Created on 2021-06-30 by the reprex package (v2.0.0)}

[Robinlovelace]

Are you sure that the code written in that function is appropriate for osmextract?

No and agree, osmextract would be be a better home for this. However... I think there are some instances where both point and polygon representations of supermarkets and other features exist.

[Robinlovelace]

See here for a reproducible example which did have some duplicate points, at least in early 2021, the idea was developed in the context of data from osmextract: https://github.com/cyipt/actdev/blob/main/code/get_pois.R