Quick Hit: Using the New Equal Earth Projection in R

September 28, 2018
By

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In my semi-daily run of brew update I noticed that proj4 had been updated to 5.2. I kinda “squeee“‘d since (as the release notes show) the Equal Earth projection was added to it (+proj=eqearth).

As the team who created the projection describes it: “The Equal Earth map projection is a new equal-area pseudocylindrical projection for world maps. It is inspired by the widely used Robinson projection, but unlike the Robinson projection, retains the relative size of areas. The projection equations are simple to implement and fast to evaluate. Continental outlines are shown in a visually pleasing and balanced way.”

They continue: “The Robinson and Equal Earth projections share a similar outer shape[…] Upon close inspection, however, the way that they differ becomes apparent. The Equal Earth with a height-to-width ratio of 1:2.05 is slightly wider than the Robinson at 1:1.97. On the Equal Earth, the continents in tropical and mid-latitude areas are more elongated (north to south) and polar areas are more flattened. This is a consequence of Equal Earth being equal-area in contrast to the Robinson that moderately exaggerates high-latitude areas.”

Here’s a comparison of it to other, similar, projections:

©Taylor & Francis Group, 2018. All rights reserved.

Map projections are a pretty nerdy thing, but this one even got the attention of Newsweek.

To use this new projection now in R, you’ll need to install the proj4 📦 from source after upgrading to the new proj4 library. That was a simple brew upgrade for me and Linux users can do the various package manager incantations to get theirs as well. Windows users can be jealous for a while until updated package binaries make their way to CRAN (or switch to a real platform 😎).

After a fresh source install of proj4 all you have to do is:

library(ggalt) # git[la|hu]b/hrbrmstr/hrbrthemes
library(hrbrthemes) # git[la|hu]b/hrbrmstr/hrbrthemes
library(ggplot2)

world <- map_data("world")

ggplot() +
  geom_map(
    map = world, data = world,
    aes(long, lat, map_id = region), 
    color = ft_cols$white, fill = ft_cols$slate,
    size = 0.125
  ) +
  coord_proj("+proj=eqearth") +
  labs(
    x = NULL, y = NULL,
    title = "Equal Earth Projection (+proj=eqearth)"
  ) +
  theme_ft_rc(grid="") +
  theme(axis.text=element_blank())

to get:

Remember, friends don't let friends use Mercator.

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