Projection close to global bbox distorts geometries

Hi,

I noticed that when I reproject a set of polygons in geopandas the polygons get distorted if they are close to the borders of the global coverage. I noticed this behavior when projecting to cylindrical equal area projection, not sure if this more general though. Here’s an example

from shapely.geometry import Point, Polygon
import geopandas as gpd
polys = gpd.GeoSeries([Point(-180,0), Point(0,0), Point(180,0), Point(-180, 90), Point(0, 90), Point(180, 90), Point(-160, 45)])
df = gpd.GeoDataFrame({'geometry': polys, 'df':range(len(polys))}, crs={'init': 'epsg:4326', 'no_defs': True})
df
df.crs
df.geometry = df.geometry.buffer(5)
df.plot()
wgs84 = {u'datum': u'WGS84', u'no_defs': True, u'proj': u'longlat'}
cea = {u'datum': u'WGS84', u'lat_ts': 0, u'lon_0': 0, u'no_defs': True, u'proj': u'cea',u'units': u'm',  u'x_0': 0, u'y_0': 0}
dfcea = df.to_crs(crs=cea).copy()
dfcea.crs
dfcea.plot()

Not sure if this is caused by the way the geometry is treated here or in shapely or geos. I imagine the solution would require an intersection with the global bbox first and then a reprojection. E.g.

bbox = gpd.GeoSeries([Polygon([(-180, 90), (180,90), (180, -90), (-180,-90)])])
dfbbox = gpd.GeoDataFrame({'geometry': bbox, 'gbbox':0}, crs={'init': 'epsg:4326', 'no_defs': True})
dfint = gpd.tools.overlay(df, dfbbox)
dfint.plot()
dfint.to_crs(crs=cea).plot()

[snowman2]

@Sieboldianus, what you have outlined in your example is similar to the internal logic of the to_crs() method in geopandas.

[snowman2]

Yes, but when using gdf.to_crs(‘ESRI:54009’) I get the FutureWarning that the proj is initialized in old style (+init).

This is addressed in the master branch currently and will no longer be an issue in version 0.7.0.