Extract from OSM Planet File is incomplete - r

Question

I'm fairly new to the OSM world and I need to extract all water related polygons from the OSM planet file, except for ocean polygons. I know there is some product from a university in Tokyo, but it's from 2016 and I need it as up to date as possible.
I already extracted a good bit of it with the following code. However, comparing the resulting layers with the OSM basemap in QGIS I noticed that some parts are missing. Even though they have the same flags and relations like other parts that were extracted. I know that some parts of rivers are digitalized as lines and not polygons, so it's okay that those are missing. The missing parts are definitely polygons, since I could extract one of them with the same flags through the QuickOSM plug-in in QGIS. Also the OSM Basemap shows clearly that those areas must be polygons (see screenshot).
Is there a mistake in my code or did I make an mistake with the flags? My code however throws no errors and everything seems to be working except for the missing parts.
Thanks in advance!
Here is the code so far:
library(gdalUtils)
library(rgdal)
library(sf)
# extracting all layers with flag "natural = water"
path_pbf <- "path/to/planet_file.osm.pbf"
ogr2ogr(src_datasource_name = path_pbf,
"OSM_Waterbodies.gpkg",
f = "GPKG",
sql = "SELECT * FROM multipolygons WHERE natural = 'water'",
progress = T)
# extracting all layers with flag "other_tags LIKE waterway"
ogr2ogr(src_datasource_name = path_pbf,
"OSM_Waterways.gpkg",
f = "GPKG",
sql = "SELECT * FROM multipolygons WHERE other_tags LIKE '%waterway%'",
progress = T)
waterways <- st_read("OSM_Waterways.gpkg")
waterways$rm <- NA
# select only certain polygons since waterways also includes dams etc
check <- "*riverbank*|*river*|*stream*|*tidal channel*|*canal*|*drain*|*ditch*|*lake*"
# mark polygons which are not part of the desired selection with "remove" flag
for(i in 1:nrow(waterways)){
if (!grepl(check, waterways$other_tags[i])){
waterways$rm[i] <- "Remove"
}
}
# drop rows with "remove" flag
index <- which(waterways$rm == "Remove")
waterways <- waterways[-index,]
st_write(waterways, "OSM_Waterways_clean.gpkg", driver = "GPKG")
P.S.: The code is probably not the most efficient one, but it's not about efficiency, since I will probably run it once or twice.

Answer 1

It looks like you're only extracting multiploygons, which are used in OSM when a shape isn't a simple polygon. This means that river sections with islands in them will be extracted, but many simple river sections will not, as they are just mapped as closed ways (An example from your screenshot). I don't have the OSM Global file on hand to check, but I would imagine that it's as simple as running the ogr2ogr functions again with ways instead of multipolygons in the SQL, and then checking that the ways are closed (likely, check that the first and last nodes are identical, as a quick search suggests that ogr2ogr doesn't provide a way to check for closed ways explicitly).