Reversed
R-bloggers 2025-11-05
[This article was first published on r.iresmi.net, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Day 5 of 30DayMapChallenge: « Earth » (previously).
What if the bathymetry of the Mediterranean Sea is reversed? We would get a Western Island and an Eastern Island, a Sardinia-Corsica Bay, the Balearic Lagoon… Let’s see!
library(terra)library(sf)terraOptions(progress=0)
A global bathymetry dataset (7.5 Go zipped NetCDF) is available at GEBCO. We crop it around the Mediterranean Sea.
med <- c(xmin = -7, ymin = 30, xmax = 39, ymax = 45) |> st_bbox() |> st_as_sfc()gebco <- rast("~/data/gebco/GEBCO_2025_sub_ice.nc") |> crop(med) We set all positive values to 0 and all negative values are inversed. The relief is more pronounced with a light lower resolution, then we compute the hillshading.
mountain_med <- aggregate((gebco <= 0) * -1 * gebco, 10, mean)slope <- terrain(mountain_med, "slope", unit = "radians")aspect <- terrain(mountain_med, "aspect", unit = "radians")hill <- shade(slope, aspect, angle = 45, direction = 315, normalize = TRUE)
Map
plot(hill, col = grey(0:255/255), main = "Mediterranean Sea upside down", legend = FALSE, mar = c(2,2,2,4))plot(mountain_med, col = topo.colors(30, alpha = 0.3), plg = list(title = "Elevation (m)"), add = TRUE)mtext(paste("data: GEBCO\nhttps://r.iresmi.net", Sys.Date()), side = 1, line = 3, cex = 0.5, adj = 1)
To leave a comment for the author, please follow the link and comment on their blog: r.iresmi.net.
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.