当使用Cartopy (Python)绘制正交绘图时，如何裁剪地图/设置图像的纬度/经度边界？

Question

我正在绘制南极附近北极的正投影。然而，我想要裁剪这些图像，这样我只能看到极地的10或度范围内的纬度，而不是一直到赤道。到目前为止，我的代码如下：

# %% Import packages 
import os 
import matplotlib.pyplot as plt
import sys
import pandas as pd
import numpy as np
from geopack import geopack 
import cartopy.crs as ccrs
import cartopy.feature as cfeature


fig = plt.figure(figsize=(20,10))

# North
ax = fig.add_subplot(1,2,1, projection=ccrs.Orthographic(central_latitude=90))
ax.stock_img()
ax.coastlines()
ax.add_feature(cfeature.BORDERS, linestyle="--")

# South
ax = fig.add_subplot(1,2,2, projection=ccrs.Orthographic(central_latitude=-90))
ax.stock_img()
ax.coastlines()
ax.add_feature(cfeature.BORDERS, linestyle="--")

plt.show() 

我的代码当前生成的绘图

任何帮助都将不胜感激。谢谢!

Answer 1

地图缩放可能不支持在Cartopy中的正投影。我尝试使用SouthNorthPolarStereo()投影，使用set_extent限制映射区域，并用循环路径裁剪绘图。输出可以满足您的要求。

​

这是密码。

# %% Import packages
#import os
import matplotlib.pyplot as plt
#import sys
#import pandas as pd
import numpy as np
#from geopack import geopack
import cartopy.crs as ccrs
import cartopy.feature as cfeature
import matplotlib.path as mpath

# ref: https://scitools.org.uk/cartopy/docs/latest/gallery/lines_and_polygons/always_circular_stereo.html#sphx-glr-gallery-lines-and-polygons-always-circular-stereo-py
def add_circle_boundary(ax):
    # Compute a circle in axes coordinates, which we can use as a boundary
    # for the map. We can pan/zoom as much as we like - the boundary will be
    # permanently circular.
    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)


fig = plt.figure(figsize=(20,10))
# South
#ax = fig.add_subplot(1,2,1, projection=ccrs.Orthographic(central_latitude=90))
#ax = fig.add_subplot(1,2,1, projection=ccrs.NorthPolarStereo())
ax = fig.add_subplot(1,2,1, projection=ccrs.SouthPolarStereo())
ax.stock_img()
ax.coastlines()
ax.gridlines()
ax.set_title('Original',fontsize = 24)
#ax.add_feature(cfeature.BORDERS, linestyle="--")
ax.set_extent([-180, 180, -90, 0], crs=ccrs.PlateCarree())
add_circle_boundary(ax)

# South zoomed
ax1 = fig.add_subplot(1,2,2, projection=ccrs.SouthPolarStereo())
ax1.stock_img()
ax1.coastlines()
ax1.gridlines()
#ax1.add_feature(cfeature.BORDERS, linestyle="--")
ax1.set_extent([-180, 180, -90, -60], crs=ccrs.PlateCarree())
ax1.set_title('Zoomed',fontsize = 24)
add_circle_boundary(ax1)

#plt.show()
plt.savefig("out.png")