Manage CRS from new geopandas release

[PyMap]

Hi all! With new gepandas release, the pyproj.CRS object has been enriched and the old way (pyproj4) to specify projection as parameter (`crs') seems to have changed considerably.

When you try to plot a gd over a a layer with display method:

# 1. Plot data:
ax = gdf.plot()

# 2. Display dinamic map
mplleaflet.display(fig=ax.figure, crs=ax.crs)

The following error is returned:

TypeError: type object argument after ** must be a mapping, not CRS

This is seems to be explained because CRS with new geopandas release has a new obtect type.

Passing the crs with the .to_dict() this error doesn't appears again, but as I'm still getting some warnings like this one:

UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()

I would like to know if this is the correct way to pass the gdf.crs as parameter in the display method.

Great work wit this library, much thanks!

[MochiYoshi]

Not sure if this is helpful but when I ran into the same problem (only being able to plot things in the default EPSG4326 crs and not being able to pass in a different crs/epsg optional argument for mplleaflet.show), I came up with this workaround:

Besides downgrading pyproj to 1.9.6 (which means you wont be able to use geopandas >= 0.7.0), what you can also do is edit the leaflet_renderer.py script, when defining the LeafletRenderer class you can substitute:

old code which works with pyproj 1.9.6 or below -
proj_in = pyproj.Proj(crs)
proj_out = pyproj.Proj(crs_out)
self.transformfunc = partial(pyproj.transform, proj_in, proj_out)

new code which works for pyproj >= 2.0.0 -
proj_in = pyproj.CRS(crs)
proj_out = pyproj.CRS(crs_out)
transformer = pyproj.Transformer.from_crs(proj_in, proj_out, always_xy=True)
self.transformfunc = partial(transformer.transform)

You should also return epsgstr rather than crs in the _crs_from_epsg(epsg) function at the bottom of leaflet_renderer.py to satisfy the new crs format used in pyproj >= 2.0.0.

Hope this helps someone :)

[PyMap]

Thanks for the workaround, I will try to take a look!