如何绘制从旋转坐标

Question

我的域的四个角的坐标是旋转坐标。 这些是 rlons：-25.6,32.48，-25.6,32.48

rlats：-27.6，-27.6,26.08,26.08

旋转的北极是 lon -170，lat 40

首先，我必须将角点从旋转坐标转换为地理坐标。

转换后，实际的地理坐标为

lons：-13.7893,39.6672,82.6967，-54.64，-13.7893

拉特：18.3262,15.9548,59.6559,64.5671,18.3262

然后我想在底图中绘制角点。但是我的代码没有做出准确的界限。准确的边界应该是弯曲的，而不是在顶部和底部的直线。

import matplotlib.pyplot as plt 
from mpl_toolkits.basemap import Basemap
import numpy as np

x_big = [-13.7893,39.6672,82.6967,-54.64,-13.7893]
y_big = [18.3262,15.9548,59.6559,64.5671,18.3262]

fig=plt.Figure()
ax = fig.add_subplot(1, 1, 1)
map = Basemap(projection='cyl', resolution = 'i', llcrnrlon=-60, llcrnrlat=5,urcrnrlon=90, urcrnrlat=70)
map.drawcoastlines()
map.drawcountries()
map.bluemarble()
map.plot(x_big, y_big, color='r', lw=5)
map.drawparallels(np.arange(5.,75.,15.),labels=[1,0,0,0])
map.drawmeridians(np.arange(-60.,90.,30.),labels=[0,0,0,1])
plt.show()

当我运行它时，它会生成一个右角的地图，但不知何故，连接角的线是直线，这是不准确的。它应该如附图所示：

Answer 1

您需要使用.drawgreatcircle（）方法而不是简单的plot（）。这是工作代码。

import matplotlib.pyplot as plt 
from mpl_toolkits.basemap import Basemap
import numpy as np

# these coordinates for points far apart
x_big = [-13.7893, 39.6672, 82.6967, -54.64, -13.7893]  # lon
y_big = [18.3262, 15.9548, 59.6559, 64.5671, 18.3262]   # lat

fig = plt.Figure()
ax = fig.add_subplot(1, 1, 1)
map = Basemap(projection='cyl', resolution = 'i', llcrnrlon=-60, \
              llcrnrlat=5, urcrnrlon=90, urcrnrlat=82)
map.drawcoastlines()
map.drawcountries()
map.bluemarble()
map.plot(x_big, y_big, color='red', lw=1)

# plot line of great circles
map.drawgreatcircle(x_big[0], y_big[0], x_big[1], y_big[1], del_s=500, lw=2, color="y")
map.drawgreatcircle(x_big[1], y_big[1], x_big[2], y_big[2], del_s=500, lw=2, color="y")
map.drawgreatcircle(x_big[2], y_big[2], x_big[3], y_big[3], del_s=500, lw=2, color="y")
map.drawgreatcircle(x_big[3], y_big[3], x_big[0], y_big[0], del_s=500, lw=2, color="y")

map.drawparallels(np.arange(5., 75., 15.), labels=[1,0,0,0])
map.drawmeridians(np.arange(-60., 90., 30.), labels=[0,0,0,1])
plt.show()

结果情节：