如何为南极立体投影创建圆形网格线标签？

Question

我正在使用南极立体投影来创建南极洲地图。我已经能够使用

Cartopy

创建网格线，但网格线的标签不是围绕地图的圆形，这正是我想要的。有没有办法让网格线标签遵循南极立体投影的圆形图案？这是我目前使用的代码：

fig = plt.figure(figsize=(12,8))
ax = plt.axes(projection=ccrs.SouthPolarStereo())
ax.set_extent([-180, 180, -90, -30], ccrs.PlateCarree())
ax.add_feature(cfeature.LAND, color='darkgrey')
ax.add_feature(cfeature.OCEAN, color='lightblue')
ax.add_feature(cfeature.COASTLINE, linewidth=1.25)

# Make the gridlines circular
gl = ax.gridlines(crs=ccrs.PlateCarree(), draw_labels=True, linewidth=1, color='gray', alpha=0.5, linestyle='--', zorder=10)

# Add circular boundary
theta = np.linspace(0, 2*np.pi, 100)
center, radius = [0.5, 0.5], 0.5
verts = np.vstack([np.sin(theta), np.cos(theta)]).T
circle = mpath.Path(verts * radius + center)

ax.set_boundary(circle, transform=ax.transAxes)

plt.tight_layout()
plt.show()

输出看起来像

Answer 1

这里是解决方案。这需要2个

gridlines()

语句来实现所需的情节。

import cartopy.crs as ccrs
import cartopy.feature as cfeature
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as  mpath

fig = plt.figure(figsize=(12,8))
ax = plt.axes(projection=ccrs.SouthPolarStereo())
ax.set_extent([-180, 180, -90, -30], ccrs.PlateCarree())
ax.add_feature(cfeature.LAND, color='darkgrey')
ax.add_feature(cfeature.OCEAN, color='lightblue')
ax.add_feature(cfeature.COASTLINE, linewidth=1.25)

# Draw meridian lines with labels around circular boundary
ax.gridlines(crs=ccrs.PlateCarree(), draw_labels=True, linewidth=1, \
                xlocs=range(-180,171,10), ylocs=[], \
                color='gray', alpha=0.5, linestyle='--', zorder=10)
# Draw concentric circles (but hide labels) for the parallels of the latitude
ax.gridlines(crs=ccrs.PlateCarree(), draw_labels=False, linewidth=1, \
                xlocs=[], ylocs=None, \
                color='gray', alpha=0.5, linestyle='--', zorder=10)

# Add circular boundary
theta = np.linspace(0, 2*np.pi, 100)
center, radius = [0.5, 0.5], 0.5
verts = np.vstack([np.sin(theta), np.cos(theta)]).T
circle = mpath.Path(verts * radius + center)

ax.set_boundary(circle, transform=ax.transAxes)


plt.tight_layout()
plt.show()

编辑

地图边界周围的标签。只能手动绘图。我已经能够想出这个情节。但是代码太乱了，等我细化了我才贴出来。对不起。