Get relief of Switzerland from a shp-file - r

Question

I would like an official source for drawing the relief over a map of Switzerland.
I downloaded https://cms.geo.admin.ch/ogd/topography/DHM25_BM_SHP.zip to use the dhm25_p.shp-File
Now using the code
aux <- st_read(dsn="dhm25_p.shp")
auxx <- as_Spatial(aux)
auxxx <- as.data.frame(auxx)
ggplot() +
# draw the relief
geom_raster(
data = auxxx,
inherit.aes = FALSE,
aes(
x = coords.x1,
y = coords.x2,
alpha = coords.x3
)
)
I'll get the error
Error in `geom_raster()`:
! Problem while converting geom to grob.
ℹ Error occurred in the 1st layer.
Caused by error:
! cannot allocate vector of size 6539542.5 Gb

Answer 1

A shapefile of points is generally not a good source for mapping continuous phenomena such as elevation. It is better to use raster data.
Here is a simple way to make an elevation map for Switzerland
library(terra)
library(geodata)
x <- geodata::elevation_30s("Switzerland", ".")
plot(x)
Add contour lines
v <- as.contour(x, levels=c(500,1000,3000))
lines(v)
Or show shaded relief
slope <- terrain(x, "slope", unit="radians")
aspect <- terrain(x, "aspect", unit="radians")
hill <- shade(slope, aspect, 40, 270)
plot(hill, col=gray(seq(0,1,.01)), legend=F, axes=F, mar=1)
To show relief and elevation
plot(hill, col=gray(seq(0,1,.01)), legend=F, axes=F)
plot(x, col=terrain.colors(25, alpha=.5), add=T, axes=F, legend=T)
You can do the same things with the Swiss government data from the website you point to in your (now hidden) answer. But it takes some more work if you want to remove the areas outside of Switzerland.
y <- rast("DHM200.asc")
# Assign the coordinate reference system (Landesvermessung 1903)
crs(y) <- "EPSG:21781"
# get the outline of the country and project it to the crs of the raster data
swz <- geodata::gadm("Switzerland", level=1, path=".")
pswz <- project(swz, y)
# remove values for areas outside of Switzerland
y <- mask(y, pswz)
plot(y)
lines (pswz)
And with ggplot you can use geom_spatraster
library(tidyterra)
library(ggplot2)
ggplot() + geom_spatraster(data = y)

Answer 2

For posterity, leveranging also on MPB_2022 and Robert, see how you can replicate the same map using ggplot2 + tidyterra (as explained in detail in https://dieghernan.github.io/202210_tidyterra-hillshade/):
library(terra)
library(geodata)
library(tidyterra)
library(ggplot2)
x <- geodata::elevation_30s("Switzerland", ".")
slope <- terrain(x, "slope", unit = "radians")
aspect <- terrain(x, "aspect", unit = "radians")
hill <- shade(slope, aspect, 40, 270)
# Hillshading, but we need a vector of colors
pal_greys <- hcl.colors(1000, "Grays")
# Get a vector of colors based on the value of shades
# Create index
hill_col <- hill %>%
# Rename layer
select(shades = 1) %>%
mutate(index_col = round(scales::rescale(shades, to = c(1, length(pal_greys))))) %>%
pull(index_col) %>%
pal_greys[.]
head(unique(hill_col), 10)
# Plot
ggplot() +
# Add our hill shade and use fill with the vector color
geom_spatraster(data = hill, fill = hill_col, maxcell = Inf, alpha = 1) +
# And add the initial raster with some alpha
geom_spatraster(data = x) +
# Add an hypstometric tint
scale_fill_hypso_tint_c(
palette = "dem_poster",
# Need alpha to show the hill
alpha = 0.5 ) +
theme_minimal() +
labs(fill="Elevation")