Add Airocean projection (formerly Dymaxion)

docs/plot/plotdefs.json

@@ -269,6 +269,18 @@
         "res": "low",
         "type": "poly"
     },
+    {
+        "filename": "airocean.png",
+        "latmax": 90,
+        "latmin": -90,
+        "lonmax": 180,
+        "lonmin": -180,
+        "name": "airocean",
+        "projstring": "+proj=airocean",
+        "res": "low",
+        "type": "line",
+        "delta_cut": 1e6
+    },
     {
         "filename": "eck1.png",
         "latmax": 90,

docs/source/operations/projections/airocean.rst

@@ -0,0 +1,57 @@
+.. _airocean:
+
+********************************************************************************
+Airocean
+********************************************************************************
+
+The Airocean map projection is a icosahedron polyhedral projection that intends
+to lay down continental landmasses into a contiguous map with minimal scale and angular
+distorsion while preserving land surfaces from (most) interruptions.
+In comparison to the Snyder's Icosahedral Equal Area, this projection relies on a specific way 
+to orient and cut the icosahedron so that most interruptions lie within the ocean. The projection
+was first invented by Buckminster Fuller in 1943 using a cuboctahedron as basis.
+The idea to use an icosahedron came later in 1954, and it wasn't until 1978 that the projection 
+was formally mathematically defined :cite:`Gray1995`.
+
++---------------------+----------------------------------------------------------+
+| **Classification**  | Polyhedral, equal area                                   |
++---------------------+----------------------------------------------------------+
+| **Available forms** | Forward and inverse, spherical                           |
++---------------------+----------------------------------------------------------+
+| **Defined area**    | Global                                                   |
++---------------------+----------------------------------------------------------+
+| **Alias**           | airocean                                                 |
++---------------------+----------------------------------------------------------+
+| **Domain**          | 2D                                                       |
++---------------------+----------------------------------------------------------+
+| **Input type**      | Geodetic coordinates                                     |
++---------------------+----------------------------------------------------------+
+| **Output type**     | Projected coordinates                                    |
++---------------------+----------------------------------------------------------+
+
+
+.. figure:: ./images/airocean.png
+   :width: 500 px
+   :align: center
+   :alt:   Airocean
+
+   proj-string: ``+proj=airocean``
+
+.. note::
+   The airocean map of the whole globe has an extent of approximatelly
+   :math:`[0, 0, 17404000, 36844000]` in meters. Although the airocean map has no
+   true up or down, the choice was made to lay it out vertically, from Antartica to Australia.
+
+
+Parameters
+################################################################################
+
+.. note:: All parameters are optional for the projection.
+
+.. include:: ../options/lon_0.rst
+
+.. include:: ../options/R.rst
+
+.. include:: ../options/x_0.rst
+
+.. include:: ../options/y_0.rst

docs/source/operations/projections/index.rst

@@ -17,6 +17,7 @@ Projections map the spherical 3D space to a flat 2D space.
    adams_ws2
    aea
    aeqd
+   airocean
    airy
    aitoff
    alsk

docs/source/references.bib

@@ -73,6 +73,18 @@ @TechReport{Deakin2004
   Url                      = {http://www.mygeodesy.id.au/documents/Molodensky%20V2.pdf}
 }
 
+@Article{Gray1995,
+  Title                    = {Exact Transformation Equations for Fuller's World Map},
+  Author                   = {Robert W. Gray},
+  Journal                  = {Cartographica},
+  Year                     = {1995},
+  Number                   = {3},
+  Pages                    = {17--25},
+  Volume                   = {32},
+
+  Doi                      = {10.3138/1677-3273-Q862-1885}
+}
+
 @Article{EberHewitt1979,
   Title                    = {Conversion algorithms for the {CalCOFI} station grid},
   Author                   = {L. E. Eber and Roger P. Hewitt},

src/lib_proj.cmake

@@ -28,6 +28,7 @@ print_variable(ENABLE_IPO)
 ##############################################
 
 set(SRC_LIBPROJ_PROJECTIONS
+  projections/airocean.cpp
   projections/aeqd.cpp
   projections/adams.cpp
   projections/gnom.cpp

src/pj_list.h

@@ -37,6 +37,7 @@ PROJ_HEAD(crast, "Craster Parabolic (Putnins P4)")
 PROJ_HEAD(defmodel, "Deformation model")
 PROJ_HEAD(deformation, "Kinematic grid shift")
 PROJ_HEAD(denoy, "Denoyer Semi-Elliptical")
+PROJ_HEAD(airocean, "Airocean Fuller")
 PROJ_HEAD(eck1, "Eckert I")
 PROJ_HEAD(eck2, "Eckert II")
 PROJ_HEAD(eck3, "Eckert III")

test/gie/builtins.gie

@@ -1162,6 +1162,112 @@ accept  -2 -1
 expect  -223377.422876954 -111701.072127637
 
 
+===============================================================================
+# Airocean
+# 	Sph., Ellps.
+# (Each of the 23 faces tested separately around their center, inverse included)
+===============================================================================
+
+-------------------------------------------------------------------------------
+operation +proj=airocean   +ellps=GRS80
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+accept 23 28
+expect 13556926.823490718 23467359.674033195
+accept 72 46
+expect 9643052.686797861 23470487.369125906
+accept 145 75
+expect 7737390.782312192 20104788.054769896
+accept -77 61
+expect 9668545.797051517 16783947.67041814
+accept -26 35
+expect 15441270.037205558 20068684.009483118
+accept 29 -13
+expect 15454500.775444025 26772291.248060163
+accept 72 -25
+expect 9646854.070149897 30174627.37899145
+accept 96 10
+expect 7748510.227719365 26793197.86531571
+accept 169 35
+expect 3879364.926075886 20112884.602338977
+accept -151 13
+expect 3855457.9788894877 13372404.237126907
+accept -108 25
+expect 7757309.887436695 13427462.802436445
+accept -84 -10
+expect 9655653.729867224 10046033.288760712
+accept -42 -5
+expect 13531956.757129436 10009950.782333512
+accept -11 -35
+expect 13524799.031510707 3365720.025783973
+accept 154 -35
+expect 1943420.8175922546 30184052.521318957
+accept -157 -28
+expect 1942090.2539895012 10076591.20216224
+accept -108 -46
+expect 7761111.270788729 6723322.792570909
+accept -35 -75
+expect 9666773.175274398 3357623.4782149
+accept 98 -48
+expect 4871988.820643149 32910398.56714167
+accept 113 -72
+expect 7725850.483813245 1088496.8256700835
+accept 143 -9
+expect 3215425.0474725077 27916795.439275663
+accept 124 7
+expect 5140625.112062726 26778848.513305675
+accept 147 15
+expect 2546085.5873131985 22379298.380909223
+
+direction inverse
+accept 13500000 23400000
+expect 23.028334260781396 29.00141845366607
+accept 9700000 23400000
+expect 70.91748976033631 46.69938767448572
+accept 7700000 20100000
+expect 145.97790022956485 74.66181692499651
+accept 9700000 16700000
+expect -76.80102747900565 59.99374652248361
+accept 15500000 20100000
+expect -25.944389921688217 34.24636404674132
+accept 15500000 26800000
+expect 28.780505935021033 -13.567140588707066
+accept 9700000 30100000
+expect 71.4679674085186 -24.079311453738754
+accept 7700000 26800000
+expect 96.5497950965985 9.88121445991218
+accept 3900000 20100000
+expect 169.13009208849755 35.254403049754224
+accept 3900000 13400000
+expect -150.64046965868116 13.481494624013168
+accept 7700000 13400000
+expect -108.66196431422468 24.604190039126202
+accept 9700000 10000000
+expect -83.45176986114532 -10.484774451578211
+accept 13500000 10000000
+expect -42.33857403889376 -5.173528026525927
+accept 13500000 3300000
+expect -10.156579309260813 -35.39429168339308
+accept 1900000 30100000
+expect 154.6981118584859 -34.09548216619245
+accept 1900000 10000000
+expect -157.1486568493204 -28.983938091775162
+accept 7700000 6700000
+expect -109.0368655953666 -46.16466623109972
+accept 9700000 3300000
+expect -32.11127170743792 -74.98612150074251
+accept 4800000 32900000
+expect 98.90848938837188 -48.50784207235999
+accept 7700000 1100000
+expect 114.00231130949376 -71.99425265168686
+accept 3200000 27900000
+expect 143.20066829467564 -8.847739058325072
+accept 5200000 26800000
+expect 123.33794956763194 6.861286881197438
+accept 2600000 22300000
+expect 147.63769509437498 15.818879769693432
+
+
 ===============================================================================
 # Eckert I
 # 	PCyl., Sph.