Add the Equal Earth projection support following what was done for Spilhaus

[joa-quim]

Number of line changes are surprisingly small.

• src/gmt_project.h — GMT_PROJ4_EQEARTH added to the 500-block enum.
• src/gmt_init.c — detect eqearth in the PROJ string; also gmt_set_geographic(GMT_IN). gmtinit_parse_J_option is never called for PROJ-only projections, so a non-global -R-100/40/-20/70 was read as Cartesian and all annotations vanished.
• src/gmt_proj.c (+52) —
  • gmtproj_proj4_pcyl_fwd/_inv: GDAL normalizes geographic lon to [-180,180] before subtracting lon_0, so with -Rg +lon_0=180 both W and E boundaries collapsed onto the west edge. Wind relative to central meridian, nudge the antimeridian GMT_PROJ_CONV_LIMIT inside.
  • gmtproj_left/right_proj4_pcyl: curved W/E edges. No analytic formula, so invert (origin[GMT_X], y) → lat, then project (west|east, lat).
• src/gmt_map.c — map_init_proj4: central meridian from +lon_0, is_world, curved edges, parallel_straight, GMT_OBL_ANNOT_NORMAL_TICKS, and projection_GMT = projection (the frame/annotation switches all test projection_GMT, which stays GMT_NO_PROJ otherwise — that was the Bad case in gmt_map_clip_path (500)). Clip path + gmt_half_map_width get the Robinson treatment.
• src/gmt_plot.c — boundary → gmtplot_basic_map_boundary; added to the proj_A list (annotate both 0 and 360).

It contains also a test/psbasemap/eqearth.sh that will break the CI because the baseline ps missing.

Can be tested tested with:

gmt coast -Rd -W0.5 -Bag -J+proj=eqearth+width=15 -png lixo

Assisted-by: Claude Opus 5.0

[Esteban82]

It works for me. I got the same figure.

[anbj]

Wasn’t this projection supported in GMT before?! I thought it was quite common..

[joa-quim]

No, it wasn't. This Guardian article brings some context. But this won't go without me saying that I find that article particularly ... silly. IMO, the Mercator projection is (was) the most important map projection to humanity as it gave the ability to sailing through oceans with a map and a compass (and a sextant). There is nothing colonial in that. UTM was colonial (created to draw the Pink-Rose maps).

[github-actions]

Summary of changed images

This is an auto-generated report of images that have changed on the DVC remote

Status	Path
added	test/baseline/psbasemap/eqearth.ps
modified	test/baseline/psbasemap/

Image diff(s)

Details

Added images

• test/baseline/psbasemap/eqearth.png

Modified images

Path	Old	New

Report last updated at commit 3f0a231

[anbj]

No, it wasn't. This Guardian article brings some context. But this won't go without me saying that I find that article particularly ... silly. IMO, the Mercator projection is (was) the most important map projection to humanity as it gave the ability to sailing through oceans with a map and a compass (and a sextant). There is nothing colonial in that. UTM was colonial (created to draw the Pink-Rose maps).

Yes, I've read about the 'new map' from UN. Thanks for the insight, and for the historical nugget about mapa cor-de-rosa; will read about it.