Fixing with Proj 9.8

environment.yml

@@ -13,10 +13,6 @@ dependencies:
   - shapely>=2.0
   - pyshp>=2.3.1
   - pyproj>=3.6.0
-  # PROJ 9.8 changes the way equicylindrical projections (PlateCarree)
-  # are transformed, which causes some issues. Temporary pin PROJ < 9.8
-  # to avoid these for now.
-  - proj<9.8
   # The testing label has the proper version of freetype included
   - conda-forge/label/testing::matplotlib-base>=3.6
 

lib/cartopy/crs.py

@@ -1352,10 +1352,7 @@ def _ellipse_boundary(semimajor=2, semiminor=1, easting=0, northing=0, n=201):
 class PlateCarree(_CylindricalProjection):
     def __init__(self, central_longitude=0.0, globe=None):
         globe = globe or Globe(semimajor_axis=WGS84_SEMIMAJOR_AXIS)
-        proj4_params = [('proj', 'eqc'), ('lon_0', central_longitude),
-                        ('to_meter', math.radians(1) * (
-                            globe.semimajor_axis or WGS84_SEMIMAJOR_AXIS)),
-                        ('vto_meter', 1)]
+        proj4_params = [('proj', 'latlong'), ('pm', central_longitude)]
         x_max = 180
         y_max = 90
         # Set the threshold around 0.5 if the x max is 180.
@@ -1385,8 +1382,8 @@ def _bbox_and_offset(self, other_plate_carree):
             central longitudes. No checking of this is done.
 
         """
-        self_lon_0 = self.proj4_params['lon_0']
-        other_lon_0 = other_plate_carree.proj4_params['lon_0']
+        self_lon_0 = self.proj4_params['pm']
+        other_lon_0 = other_plate_carree.proj4_params['pm']
 
         lon_0_offset = other_lon_0 - self_lon_0
 
@@ -1414,7 +1411,8 @@ def quick_vertices_transform(self, vertices, src_crs):
         if return_value is None and isinstance(src_crs, PlateCarree):
             self_params = self.proj4_params.copy()
             src_params = src_crs.proj4_params.copy()
-            self_params.pop('lon_0'), src_params.pop('lon_0')
+            self_params.pop('pm')
+            src_params.pop('pm')
 
             xs, ys = vertices[:, 0], vertices[:, 1]
 
@@ -1440,6 +1438,12 @@ def quick_vertices_transform(self, vertices, src_crs):
 
         return return_value
 
+    def as_geodetic(self):
+        from pyproj import CRS as P_CRS
+        d = self.geodetic_crs.to_json_dict()
+        d['datum'].pop('prime_meridian', None)
+        return CRS(P_CRS.from_json_dict(d))
+
 
 class TransverseMercator(Projection):
     """

lib/cartopy/tests/mpl/test_gridliner.py

@@ -11,7 +11,7 @@
 import matplotlib.ticker as mticker
 import numpy as np
 import pytest
-from shapely.geos import geos_version
+from shapely import geos_version
 
 import cartopy.crs as ccrs
 from cartopy.mpl.geoaxes import GeoAxes