The giant French Olympic-size swimming pool
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Day 8 of 30DayMapChallenge: « Openstreetmap » (previously).
What if all private swimming pools could be merged into one 25 m width pool? OSM is not just a map, it’s a database, so ask OSM… I know that not all swimming pools are present in OSM, but it’s just an exercise 🙂 and it can give us an order of magnitude or at least a minimum.
We will use a simplified map of France in the background and ask to the Overpass API (with {osmdata}) all « leisure=swimming_pool » and « access=private ». It takes 6 hours and 15 Go of RAM…
library(dplyr) library(readr) library(ggplot2) library(sf) library(osmdata) library(ggspatial) library(glue) library(httr) library(units) fr_bbox <- getbb("France métropolitaine", featuretype = "area") # GET("http://r.iresmi.net/wp-content/uploads/2021/12/adminexpress_simpl.gpkg_.zip", # write_disk("~/adminexpress_simpl.gpkg_.zip")) # dir.create("~/adminexpress") # unzip("~/adminexpress_simpl.gpkg_.zip", exdir = "~/data/adminexpress") fr <- read_sf("~/data/adminexpress/adminexpress_cog_simpl_000_2022.gpkg", layer = "region") |> filter(insee_reg > "06") # 6 hours pool <- opq(fr_bbox, timeout = 600) |> add_osm_feature(key = "leisure", value = "swimming_pool") |> add_osm_feature(key = "access", value = "private") |> osmdata_sf() pool_p <- pool$osm_polygons |> select(osm_id) pool_mp <- pool$osm_multipolygons |> select(osm_id) rm(pool) ; gc() # keep only pools in France (bbox was wider) pool_fr <- pool_p |> bind_rows(pool_mp) |> st_filter(fr) |> mutate(area = st_area(geometry)) # what resulting dimension ? olympic_pool_dim <- pool_fr |> st_drop_geometry() |> summarise(total_area = drop_units(sum(area, na.rm = TRUE))) |> mutate(width = 25, length = total_area / width) # rotate sf object rot <- function(a) matrix(c(cos(a), sin(a), -sin(a), cos(a)), 2, 2) # create the pool, translate it in France and rotate olympic_pool <- c(0, 0, 0, olympic_pool_dim$length, olympic_pool_dim$width, olympic_pool_dim$length, olympic_pool_dim$width, 0, 0, 0) |> matrix(ncol = 2, byrow = TRUE) |> list() |> st_polygon() |> st_sfc(crs = "EPSG:2154") * rot(pi / 4) + c(400000, 6300000) # map fr |> st_transform("EPSG:2154") |> ggplot() + geom_sf() + geom_sf(data = st_sf(olympic_pool, crs = "EPSG:2154"), color = "blue") + labs(title = "The giant French Olympic-size swimming pool", subtitle = glue("What if all private swimming pools could be merged into one 25 m width pool?"), caption = glue("pool data from © OpenStreetMap contributors map IGN Adminexpress r.iresmi.net - {Sys.Date()}")) + annotation_scale(height = unit(0.1, "cm")) + theme_minimal() + theme(panel.grid = element_blank(), axis.text = element_blank())
We get an Olympic swimming pool (25 m width) measuring at least 755 km in length!
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