Undesirable line through Antarctica when using GSHHS

[esc24]

PR #126 provides support for GSHHS coastlines. The source for this feature are shapefiles available from http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html. When viewed in PlateCarree the combination of two geometries to form Antartica leads to a vertical line at longitude=0 though the continent. Investigate the cause of this artefact and fix it.

[cpelley]

Confirmed that this issue is still present:

import cartopy.feature as cfeature
import matplotlib.pyplot as plt
import cartopy.crs as ccrs

ax = plt.axes(projection=ccrs.PlateCarree())
ax.stock_img()
ax.add_feature(cfeature.GSHHSFeature('coarse', edgecolor='red'))
plt.show()

I think we should modify the milestone for this issue to 0.12.0, @pelson?

[QuLogic]

The GSHHS shapes are basically like this. The Antarctica polygon is in fact two, one from -180 to 0 and one from 0 to 180. Unless we do some polygon merging, this line is not going away.

In fact, if you use a different central longitude (like say 30), you get two lines:

[pelson]

The GSHHS shapes are basically like this.

I agree. Happy enough for this to be addressed in cartopy, but fundamentally, it is an issue with the data itself.

[robbiemallett]

For people viewing this issue, I've just been shown how to draw over the 'undesirable line' with a line of the same color as the land fill like this:

import cartopy.feature as cfea

ax.plot([180, 180], [-90, -85],
                 zorder=3, color=cfea.COLORS['land'],
                 linewidth=2,
                 transform=ccrs.PlateCarree())

A horrible hack, but worked for me so might be useful for some