Example in 7.6 is only correct for Plate Carree

[Chris Willoughby]

Hi,
nice work, however I believe that the KDE example in 7.6 is not quite correct, with the errors apparent if you choose any other projection than Plate Carree (x=longitude, y=latitude).

Specifically the first call to scatter:

ax.scatter(x, y, color='r', s=.5, alpha=.25)

should be something like:

ax.scatter(x, y, color='r', s=.5, alpha=.25, transform=ccrs.Geodetic())

as your source data is in lon/lat.

If you were to replace the whole cell with:

mcrs = ccrs.Mercator()
ax = plt.axes(projection=mcrs)
ax.stock_img()
ax.scatter(x, y, color='r', s=.5, alpha=.25, transform=ccrs.Geodetic())

then the data does not display correctly without the transform argument.

In the cell with:

geo = ccrs.Geodetic()
h = geo.transform_points(crs, x, y)[:, :2].T

you are actually transforming the data from Plate Carree to Geodetic, not the other way around. This, again, is only working because x=lon, y=lat.

Hope this make sense,
Regards,
Chris.