dieghernan

Posted on Nov 12 Originally published at dieghernan.github.io on Oct 23 AI-assisted

Let’s peel the world

#rstats #giscor #maps

What would happen if we peeled the Earth like an orange? The interrupted Goode homolosine projection gives us something close to that! This equal-area projection preserves relative areas while splitting the world map into lobes. Add a few shades of orange and our world is ready to peel.

Let’s make it with sf , giscoR and ggplot2. First, we get the coastlines and draw the outline, following the cuts between the lobes.

library(sf)
library(ggplot2)
library(giscoR)
library(showtext)

world <- gisco_get_coastal_lines(resolution = 10)
goode_crs <- "+proj=igh"
lat <- c(90:-90, rep(c(-90:0, 0:-90), 3), -90:90, 90:0, 0:90, 90)
lon <- c(
  rep(180, 181),
  rep(c(80.01, 79.99, -19.99, -20.01, -99.99, -100.01), each = 91),
  rep(-180, 181),
  rep(c(-40.01, -39.99), each = 91),
  180
)
outline <- st_sfc(st_polygon(list(cbind(lon, lat))), crs = 4326) |>
  st_transform(goode_crs)
rectangle <- st_as_sfc(st_bbox(outline) * 1.1)
mask <- st_difference(rectangle, outline)

Next, we draw the meridians and parallels within each lobe so that they do not connect across the cuts.

lobes <- list(
  c(-180, -40, 0, 90), c(-40, 180, 0, 90),
  c(-180, -100, -90, 0), c(-100, -20, -90, 0),
  c(-20, 80, -90, 0), c(80, 180, -90, 0)
)
lines <- lapply(lobes, function(b) {
  west <- b[1] + 0.01
  east <- b[2] - 0.01
  south <- max(b[3], -89.99)
  north <- min(b[4], 89.99)
  meridians <- seq(-180, 180, 30)
  meridians <- meridians[meridians > west & meridians < east]
  parallels <- seq(-60, 60, 30)
  parallels <- parallels[parallels >= south & parallels <= north]
  c(
    lapply(meridians, function(x) {
      st_linestring(cbind(x, seq(south, north, length.out = 181)))
    }),
    lapply(parallels, function(y) {
      st_linestring(cbind(seq(west, east, length.out = 361), y))
    })
  )
})
grat <- st_sfc(do.call(c, lines), crs = 4326) |>
  st_transform(goode_crs)

Finally, we add the orange palette. The mask hides anything outside the outline and keeps the edges of our peel tidy.

font_add_google("Coiny", family = "coiny")

showtext_auto()

ggplot() +
  geom_sf(data = outline, fill = "#FFF0D9", colour = NA) +
  geom_sf(data = world, fill = "#F9B566", colour = "#B34D08", linewidth = 0.25) +
  geom_sf(data = grat, fill = NA, colour = "#E8A45B", linewidth = 0.25) +
  geom_sf(data = mask, fill = "#fcf1e7", colour = NA) +
  geom_sf(data = outline, fill = NA, colour = "#E87516", linewidth = 0.4) +
  coord_sf(
    crs = goode_crs,
    xlim = st_bbox(outline)[c("xmin", "xmax")],
    ylim = st_bbox(outline)[c("ymin", "ymax")],
    expand = FALSE,
    datum = NA
  ) +
  theme_void() +
  theme(
    text = element_text(family = "coiny"),
    plot.background = element_rect(fill = "#fcf1e7", colour = NA),
    plot.title = element_text(
      color = "#E87516", face = "bold", size = rel(3),
      margin = margin(b = 10)
    ),
    plot.margin = margin(10, 10, 10, 10),
    plot.caption = element_text(
      color = "#E87516", size = rel(1.5),
      margin = margin(t = 10)
    )
  ) +
  labs(
    title = "Let's peel the world",
    caption = "Interrupted Goode homolosine projection"
  )

References

Panaïotis, T. (2026, September 29). Projections cartographiques : Le guide pour ne pas y laisser sa santé mentale. Pyranhia. Article
Wilke, C. O. (n.d.). Interrupted Goode homolosine. practicalgg. https://wilkelab.org/practicalgg/articles/goode.html (Source for the outline and masking approach.)

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Let’s peel the world

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