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Added winkel tripel projection class #2442

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d550f65
Added winkel tripel projection class
AgentOxygen Sep 25, 2024
6210860
Cleaned up WinkelTripel super constructor
AgentOxygen Oct 7, 2024
1511ceb
Merge branch 'SciTools:main' into main
AgentOxygen Apr 24, 2025
de76b10
Added Winkel Tripel test
AgentOxygen Apr 24, 2025
31dc6c7
Added baseline image for Winkel Tripel projection
AgentOxygen Apr 24, 2025
ced358f
Update lib/cartopy/crs.py
greglucas May 23, 2025
0d1baff
Update lib/cartopy/crs.py
greglucas May 23, 2025
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27 changes: 27 additions & 0 deletions lib/cartopy/crs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2539,6 +2539,33 @@ def transform_points(self, src_crs, x, y, z=None, trap=False):
return result


class WinkelTripel(_WarpedRectangularProjection):
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@greglucas greglucas Sep 25, 2024

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Do we need to do any of the nan handling here like we are doing in the Robinson projection? i.e. should this subclass Robinson instead if it is similar to that?

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@AgentOxygen AgentOxygen Oct 7, 2024

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I was able to generate maps containing maps with no problem. Are there other tests for nans that I would need to do?

"""
A Winkel-Tripel projection.

Compromise modified azimuthal projection that is less distorted
and more area-accurate. It is comparable to the Robinson
projection in both appearance and popularity.

The National Geographic Society uses the Winkel-Tripel projection
for most of the maps they produce.
"""

def __init__(self, central_longitude=0.0, globe=None):
globe = globe or Globe(semimajor_axis=WGS84_SEMIMAJOR_AXIS)
proj4_params = [('proj', 'wintri'),
('lon_0', central_longitude),
('lat_0', 0.0)]
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@greglucas greglucas Sep 25, 2024

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Do we need to pass in the lat_0 parameter even if 0 is the default, and does that even work, it looks like it is lat_1 in the documentation: https://proj.org/en/9.4/operations/projections/wintri.html

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@AgentOxygen AgentOxygen Apr 24, 2025

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lat_0 is required and lat_1 doesn't work. Maybe this is a typo in proj? I'm also not very familiar with that library so maybe I'm hacking a parameter.

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@greglucas greglucas Apr 28, 2025

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I don't think lat_0 is required when I tried this out locally. It looks like it may actually be ignored within proj. lat_1 does work for me and is the first standard parallel. For now, I would just remove the lat_0 from this list. In addition, all of our other _WarpedRectangularProjection subclasses also accept the false_easting and false_northing, so could you pipe those through the initializer as well for consistency with the other classes?

Analysis:
All of these produce a pyproj CRS, but there are differences in the WKT which I think the lat_0 indicates isn't being forwarded because it has a "REMARK" at the end. You can also look at the first standard parallel and the first and second are identical, whereas the third (with lat_1) does have the expected 5.

import pyproj
pyproj.CRS.from_proj4("proj=+wintri").to_wkt()
pyproj.CRS.from_proj4("proj=+wintri +lat_0=5").to_wkt()
pyproj.CRS.from_proj4("proj=+wintri +lat_1=5").to_wkt()
'PROJCRS["unknown",BASEGEOGCRS["unknown",DATUM["World Geodetic System 1984",ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]],ID["EPSG",6326]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8901]]],CONVERSION["unknown",METHOD["Winkel Tripel"],PARAMETER["Longitude of natural origin",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Latitude of 1st standard parallel",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8823]],PARAMETER["False easting",0,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",0,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["(E)",east,ORDER[1],LENGTHUNIT["metre",1,ID["EPSG",9001]]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1,ID["EPSG",9001]]]]'
'PROJCRS["unknown",BASEGEOGCRS["unknown",DATUM["World Geodetic System 1984",ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]],ID["EPSG",6326]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8901]]],CONVERSION["unknown",METHOD["Winkel Tripel"],PARAMETER["Longitude of natural origin",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Latitude of 1st standard parallel",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8823]],PARAMETER["False easting",0,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",0,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["(E)",east,ORDER[1],LENGTHUNIT["metre",1,ID["EPSG",9001]]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1,ID["EPSG",9001]]],REMARK["PROJ CRS string: +proj=wintri +lat_0=5"]]'
'PROJCRS["unknown",BASEGEOGCRS["unknown",DATUM["World Geodetic System 1984",ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]],ID["EPSG",6326]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8901]]],CONVERSION["unknown",METHOD["Winkel Tripel"],PARAMETER["Longitude of natural origin",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Latitude of 1st standard parallel",5,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8823]],PARAMETER["False easting",0,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",0,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["(E)",east,ORDER[1],LENGTHUNIT["metre",1,ID["EPSG",9001]]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1,ID["EPSG",9001]]]]'


super().__init__(proj4_params,
central_longitude,
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@greglucas greglucas Apr 28, 2025

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Should be indented the same amount as the parentheses, see the other classes in this file for an example.

globe=globe)

@property
def threshold(self):
return 1e4


class InterruptedGoodeHomolosine(Projection):
"""
Composite equal-area projection emphasizing either land or
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Binary file added ...s/mpl/baseline_images/mpl/test_mpl_integration/test_global_map_WinkelTripel.png
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1 change: 1 addition & 0 deletions lib/cartopy/tests/mpl/test_mpl_integration.py
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Expand Up @@ -196,6 +196,7 @@ def test_simple_global():
(ccrs.ObliqueMercator, dict(azimuth=90., central_latitude=-22)),
id='ObliqueMercator_rotated',
),
ccrs.WinkelTripel,
])
@pytest.mark.mpl_image_compare(style='mpl20')
def test_global_map(proj):
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