Variations on map projections in R
Posted on May 20, 2022
Part 3 of 3 in the series: Making Maps in R
In this example we will:
- Use some crazy projections
- Do some themeing for our maps
Inspired by https://xkcd.com/977/
Requirements:
Rggplot2sfrnaturalearthlwgeomcowplotrnaturalearthhiresrnaturalearthdata
If you have difficulties installing rnaturalearth and sf natively on your system,
I have found it possible by installing R and the packages in a conda environment.
I explain how to do this, here.
This post is part of a series about making maps in R:
Getting started
library("rnaturalearth")
library("ggplot2")
library(sf)
library(lwgeom)
library(cowplot)
# You also need to install rnaturalearthhires for this to work.
# devtools::install_github("ropensci/rnaturalearthhires")
# devtools::install_github("ropensci/rnaturalearthdata")
# Get some data to put on the map
label_frame <- data.frame("Label" = c("Brisbane", "Perth"), "Lat" = c(-27.4705, -31.9523), "Lon" = c(153.0260, 115.8613))
label_frame <- st_as_sf(x=label_frame, coords = c("Lon", "Lat"), crs = "EPSG:4326")
Projections in R
I will post the projection and the R script stuff below it.
Van der Grinten (4)
options(repr.plot.width=12, repr.plot.height=8)
world_sf <- ne_countries(returnclass = "sf")
# Themed with minimal grid from cowplot
world <- ggplot() +
geom_sf(data = world_sf ) +
ggtitle("van der Grinten IV")+
theme_minimal_grid()+
coord_sf(crs= "+proj=vandg4")
world
Robinson Projection
world_sf <- ne_countries(returnclass = "sf")
world <- ggplot() +
geom_sf(data = world_sf, fill= "antiquewhite") +
geom_sf_label(data = label_frame, aes(label = Label)) +
coord_sf(crs= "+proj=robin") +
theme_minimal_grid() +
ggtitle("Robinson projection")
world
Winkel triple projection
From: https://wilkelab.org/practicalgg/articles/Winkel_tripel.html
crs_wintri <- "+proj=wintri +datum=WGS84 +no_defs +over"
world_wintri <- st_transform_proj(world_sf, crs = crs_wintri)
grat_wintri <-
st_graticule(lat = c(-89.9, seq(-80, 80, 20), 89.9)) %>%
st_transform_proj(crs = crs_wintri)
ggplot(world_wintri) +
geom_sf(size = 0.5/.pt) +
geom_sf(data = grat_wintri, color = "gray30", size = 0.25/.pt) +
coord_sf(datum = NULL) +
theme_map() +
ggtitle("Winkel tripel projection")
Interrupted Goode Homolosine projection
From https://wilkelab.org/practicalgg/articles/goode.html
options(repr.plot.width=12, repr.plot.height=8)
world_sf <- ne_countries(returnclass = "sf")
crs_goode = "+proj=igh"
# projection outline in long-lat coordinates
lats <- c(
90:-90, # right side down
-90:0, 0:-90, # third cut bottom
-90:0, 0:-90, # second cut bottom
-90:0, 0:-90, # first cut bottom
-90:90, # left side up
90:0, 0:90, # cut top
90 # close
)
longs <- c(
rep(180, 181), # right side down
rep(c(80.01, 79.99), each = 91), # third cut bottom
rep(c(-19.99, -20.01), each = 91), # second cut bottom
rep(c(-99.99, -100.01), each = 91), # first cut bottom
rep(-180, 181), # left side up
rep(c(-40.01, -39.99), each = 91), # cut top
180 # close
)
goode_outline <-
list(cbind(longs, lats)) %>%
st_polygon() %>%
st_sfc(
crs = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"
)
goode_outline <- st_transform(goode_outline, crs = crs_goode)
# get the bounding box in transformed coordinates and expand by 10%
xlim <- st_bbox(goode_outline)[c("xmin", "xmax")]*1.1
ylim <- st_bbox(goode_outline)[c("ymin", "ymax")]*1.1
# turn into enclosing rectangle
goode_encl_rect <-
list(
cbind(
c(xlim[1], xlim[2], xlim[2], xlim[1], xlim[1]),
c(ylim[1], ylim[1], ylim[2], ylim[2], ylim[1])
)
) %>%
st_polygon() %>%
st_sfc(crs = crs_goode)
# calculate the area outside the earth outline as the difference
# between the enclosing rectangle and the earth outline
goode_without <- st_difference(goode_encl_rect, goode_outline)
world <- ggplot(data = world_sf) +
geom_sf(size = 0.5/.pt) +
geom_sf(data = goode_without, fill = "white", color = "NA") +
coord_sf(crs = crs_goode) +
theme_minimal_grid()+
ggtitle("Interrupted Goode Homolosine projection")
world
Hobo Dyer projection
A lot of these projections like Gall Peters and Hobo Dyer are Equal Area Cylindrical projections with specific settings.
options(repr.plot.width=12, repr.plot.height=8)
world_sf <- ne_countries(returnclass = "sf")
world <- ggplot() +
geom_sf(data = world_sf, color = "grey", fill = "black") +
ggtitle("Hobo Dyer projection")+
theme_map()+
coord_sf(crs= "+proj=cea +lon_0=0 +lat_ts=37.5 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs")
world
Equidistant Cylindrical (Plate Carrée)
options(repr.plot.width=12, repr.plot.height=8)
world_sf <- ne_countries(returnclass = "sf")
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Equidistant Cylindrical (Plate Carrée)") +
theme_minimal_grid()+
coord_sf(crs= "+proj=eqc") +
theme(panel.grid.major = element_line(color = gray(.5), linetype = "dashed", size = 0.5),
panel.background = element_rect(fill = "aliceblue"))
world
Globes!
A lot of options for a globe Orthographic (+proj=ortho) works fine but the proportions look a bit flat.
- Geostationary Satellite View :
+proj=geos +h=35785831.0 +lon_0=-70 +sweep=y - There's also Near-sided perspective:
+proj=nsper +h=3000000 +lat_0=-23 +lon_0=130 - Lambert azimuthal equal-area projection is another option
options(repr.plot.width=12, repr.plot.height=8)
world_sf <- ne_countries(returnclass = "sf")
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Near-sided perspective") +
theme_minimal_grid()+
coord_sf(crs= "+proj=nsper +h=3000000 +lat_0=-23 +lon_0=130")
world
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Geostationary Satellite View") +
theme_minimal_grid()+
coord_sf(crs= "+proj=geos +h=35785831.0 +lon_0=20 +sweep=y ")
world
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Lambert azimuthal equal-area projection") +
theme_minimal_grid()+
coord_sf(crs= "+proj=laea +x_0=0 +y_0=0 +lon_0=-74 +lat_0=40")
world
Peirce Quincuncial & Waterman butterfly
Doesn't really work, I don't think it is supported. Someone implemented something for R here: https://github.com/cspersonal/peirce-quincuncial-projection
Waterman butterfly is also not implemented either.
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Peirce Quincuncial") +
coord_sf(crs= "+proj=peirce_q +lon_0=25 +shape=square")
world
Gall Peters projection
A lot of these projections like Gall Peters and Hobo Dyer are Equal Area Cylindrical projections with specific settings.
world <- ggplot() +
geom_sf(data = world_sf) +
ggtitle("Gall Peters projection") +
theme_minimal_grid()+
coord_sf(crs= "+proj=cea +lon_0=0 +x_0=0 +y_0=0 +lat_ts=45 +ellps=WGS84 +datum=WGS84 +units=m +no_defs")
world
gall.png
Series
Making Maps in R
A comprehensive guide to creating beautiful maps in R, from basics to advanced projections