How to draw circle in basemap or add artiste

问题

I want to know how can i plot a circle with Basemap using latitude and longitude.

import matplotlib.pyplot as plt
fig,ax = plt.subplots()
ax.axis([0,10,0,10])
circle1 = plt.Circle((5, 5), 2, color='black',fill=False)
x = ax.add_artist(circle1)
plt.show()

I want to do the same but with x,y,radius as lon lat in my basemap graph

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

m = Basemap(projection="mill", #miller est une projection connu
    llcrnrlat =0,#lower left corner latitude
    llcrnrlon =0,
    urcrnrlat =10, #upper right lat
    urcrnrlon =10,
    resolution = "l") #c croud par defaut, l low , h high , f full 
m.drawcoastlines() #dessiner les lignes
m.drawcountries()
m.drawstates()
m.drawcounties(color="b")
#m.fillcontinents() #colorier les payes
#m.etopo()

x,y=m(5,5)
m.plot(x,y,"o")
plt.show()

回答1:

Having the two codes ready you can just copy the one into the other. The only problem may be that the circle radius needs to be calculated in map coordinates,

r = 2
x,y=m(5,5)
x2,y2 = m(5,5+r) 
circle1 = plt.Circle((x, y), y2-y, ..)

Complete example:

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

fig,ax = plt.subplots()

m = Basemap(projection="mill", #miller est une projection connu
    llcrnrlat =0,#lower left corner latitude
    llcrnrlon =0,
    urcrnrlat =10, #upper right lat
    urcrnrlon =10,
    resolution = "l", ax=ax) #c croud par defaut, l low , h high , f full 
m.drawcoastlines() #dessiner les lignes
m.drawcountries()
m.drawstates()
m.drawcounties(color="b")

x,y=m(5,5)
x2,y2 = m(5,5+2) 
circle1 = plt.Circle((x, y), y2-y, color='black',fill=False)
ax.add_patch(circle1)
plt.show()

回答2:

So I'm not sure the radius that you want your circle in your map, but this code will draw you a circle polygon on top of your map m:

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
from matplotlib.patches import Circle

m = Basemap(projection="mill", #miller est une projection connu
    llcrnrlat =0,#lower left corner latitude
    llcrnrlon =0,
    urcrnrlat =10, #upper right lat
    urcrnrlon =10,
    resolution = "l") #c croud par defaut, l low , h high , f full

For the circle here, I just arbitrarily chose a radius of 1/3 the entire length of your y-axis...

circle = Circle(xy=m(5,5),radius=(m.ymax - m.ymin) / 3, fill=False)
plt.gca().add_patch(circle)

m.drawcoastlines() #dessiner les lignes
m.drawcountries()
m.drawstates()
plt.show()

来源：https://stackoverflow.com/questions/49134634/how-to-draw-circle-in-basemap-or-add-artiste

标签

python

matplotlib

matplotlib-basemap