球极平面投影

一种保形投影。地图上绘制的绿色形状是地球表面上的等面积圆。它们被称为“蒂索指示椭圆”，可用于显示地图投影的角度和面积变形。在保形投影中，圆的形状得以保留，但面积不保留。在等面积投影中，面积得以保留，但形状不保留。

from mpl_toolkits.basemap import Basemap
import numpy as np
import matplotlib.pyplot as plt
# setup stereographic basemap.
# lat_ts is latitude of true scale.
# lon_0,lat_0 is central point.
m = Basemap(width=12000000,height=8000000,
            resolution='l',projection='stere',\
            lat_ts=50,lat_0=50,lon_0=-107.)
m.drawcoastlines()
m.fillcontinents(color='coral',lake_color='aqua')
# draw parallels and meridians.
m.drawparallels(np.arange(-80.,81.,20.))
m.drawmeridians(np.arange(-180.,181.,20.))
m.drawmapboundary(fill_color='aqua') 
# draw tissot's indicatrix to show distortion.
ax = plt.gca()
for y in np.linspace(m.ymax/20,19*m.ymax/20,9):
    for x in np.linspace(m.xmax/20,19*m.xmax/20,12):
        lon, lat = m(x,y,inverse=True)
        poly = m.tissot(lon,lat,1.5,100,\
                        facecolor='green',zorder=10,alpha=0.5)
plt.title("Stereographic Projection")
plt.show()

(源代码)

../_images/stere.png