Implementation of Equal Earth projection (#1090)

Implement the Equal Earth projection (closes #1085) 

5 files changed, 80 insertions, 0 deletions

diff --git a/docs/plot/plotdefs.json b/docs/plot/plotdefs.json
index b61466f0..c494d6a7 100644
--- a/docs/plot/plotdefs.json
+++ b/docs/plot/plotdefs.json
@@ -308,6 +308,17 @@
         "type": "poly"
     },
     {
+        "filename": "eqearth.png",
+        "latmax": 90,
+        "latmin": -90,
+        "lonmax": 180,
+        "lonmin": -180,
+        "name": "eqearth",
+        "projstring": "+proj=eqearth",
+        "res": "low",
+        "type": "poly"
+    },
+    {
         "filename": "euler.png",
         "latmax": 90,
         "latmin": -90,
diff --git a/docs/source/operations/projections/eqearth.rst b/docs/source/operations/projections/eqearth.rst
new file mode 100644
index 00000000..e8b9417d
--- /dev/null
+++ b/docs/source/operations/projections/eqearth.rst
@@ -0,0 +1,59 @@
+.. _eqearth:
+
+********************************************************************************
+Equal Earth
+********************************************************************************
++---------------------+--------------------------------------------------------+
+| **Classification**  | Pseudo cylindrical                                     |
++---------------------+--------------------------------------------------------+
+| **Available forms** | Forward and inverse, spherical projection              |
++---------------------+--------------------------------------------------------+
+| **Defined area**    | Global                                                 |
++---------------------+--------------------------------------------------------+
+| **Alias**           | eqearth                                                |
++---------------------+--------------------------------------------------------+
+| **Domain**          | 2D                                                     |
++---------------------+--------------------------------------------------------+
+| **Input type**      | Geodetic coordinates                                   |
++---------------------+--------------------------------------------------------+
+| **Output type**     | Projected coordinates                                  |
++---------------------+--------------------------------------------------------+
+
+
+
+.. image:: ./images/eqearth.png
+   :alt:   Equal Earth
+
+
+The Equal Earth projection is intended for making world maps. Equal Earth is a 
+projection inspired by the Robinson projection, but unlike
+the Robinson projection retains the relative size of areas. The projection
+was designed in 2018 by Bojan Savric, Tom Patterson and Bernhard Jenny :cite:`Savric2018`.
+
+
+Usage
+###############################################################################
+
+The Equal Earth projection has no special options. Here is
+an example of an forward projection on a sphere with a radius of 1 m::
+
+    $ echo 122 47 | src/proj +proj=eqearth +R=1
+    1.55	0.89
+
+Parameters
+################################################################################
+
+.. note:: All parameters for the projection are optional.
+
+.. include:: ../options/lon_0.rst
+
+.. include:: ../options/R.rst
+
+.. include:: ../options/x_0.rst
+
+.. include:: ../options/y_0.rst
+
+Further reading
+################################################################################
+
+#. Bojan Savric, Tom Patterson & Bernhard Jenny (2018). `The Equal Earth map projection <https://www.researchgate.net/profile/Bojan_Savric2/publication/326879978_The_Equal_Earth_map_projection/links/5b69d0ae299bf14c6d951b77/The-Equal-Earth-map-projection.pdf>`_, International Journal of Geographical Information Science
diff --git a/docs/source/operations/projections/images/eqearth.png b/docs/source/operations/projections/images/eqearth.png
new file mode 100644
index 00000000..04d23c2d
--- /dev/null
+++ b/docs/source/operations/projections/images/eqearth.png
diff --git a/docs/source/operations/projections/index.rst b/docs/source/operations/projections/index.rst
index 77decd6c..a48eabe6 100644
--- a/docs/source/operations/projections/index.rst
+++ b/docs/source/operations/projections/index.rst
@@ -40,6 +40,7 @@ Projections map the spherical 3D space to a flat 2D space.
    eck6
    eqc
    eqdc
+   eqearth
    euler
    etmerc
    fahey
diff --git a/docs/source/references.bib b/docs/source/references.bib
index aceeb6cc..bd3089ee 100644
--- a/docs/source/references.bib
+++ b/docs/source/references.bib
@@ -196,6 +196,15 @@
   Year                     = {1993}
 }
 
+@Article{Savric2018,
+  Author                   = {B. Šavrič and T. Patterson and B. Jenny},
+  Title                    = {The Equal Earth map projection},
+  Journal                  = {International Journal of Geographical Information Science},
+  Year                     = {2018},
+  Publisher                = {Taylor & Francis},
+  Doi                      = {10.1080/13658816.2018.1504949},
+  Url                      = {https://www.researchgate.net/profile/Bojan_Savric2/publication/326879978_The_Equal_Earth_map_projection/links/5b69d0ae299bf14c6d951b77/The-Equal-Earth-map-projection.pdf}
+}
 
 @Article{Snyder1988,
   Author                   = {J. P. Snyder },