cartopy shapefile 变成了一个点

Question

我正在尝试从底图切换到 cartopy，但在绘制简单的 shapefile 时遇到了一些困难。

使用底图我可以得到这个

代码：

from mpl_toolkits.basemap import Basemap
# define map extent
lllat=1.1497
urlat=1.5133
lllon=103.5822
urlon=104.1579

# Set up Basemap instance
m = Basemap(
    projection = 'merc',
    llcrnrlon = lllon, llcrnrlat = lllat, urcrnrlon = urlon, urcrnrlat = urlat,
    resolution='h')

shp_info = m.readshapefile('singapore_shapefile',
                            'singapore',
                            drawbounds=True)

但是使用 cartopy，我得到一个中间有一个点的空白。

import cartopy.crs as ccrs
import cartopy.io.shapereader as shpreader
from cartopy.feature import ShapelyFeature

# define map extent
lllat=1.1497
urlat=1.5133
lllon=103.5822
urlon=104.1579

# Set up cartopy instance
m = ccrs.Mercator()
ax = plt.axes(projection=m)
plt.gcf().set_size_inches(20, 10)

reader = shpreader.Reader("singapore_shapefile")
shape_feature = ShapelyFeature(reader.geometries(), m, facecolor="w", 
                               edgecolor='black', lw=1)
ax.add_feature(shape_feature)

plt.savefig("test.png")

谁能指出我正确的方向？

形状文件：https://drive.google.com/file/d/1suB-VD65bmwesJo01mAvVUolRReWUkdV/view?usp=sharing

Answer 1

需要注意两点：

1. 您需要设置地图范围，否则，感兴趣的区域对于整个世界来说太小了。
2. ShapelyFeature 函数需要 shapefile 的投影而不是地图。

下面是修改后的代码。

import cartopy.crs as ccrs
import cartopy.io.shapereader as shpreader
from cartopy.feature import ShapelyFeature
import matplotlib.pyplot as plt

# define map extent
lllat=1.1497
urlat=1.5133
lllon=103.5822
urlon=104.1579

# Set up cartopy instance
m = ccrs.Mercator()
ax = plt.axes(projection=m)

plt.gcf().set_size_inches(20, 10)


extent=[lllon,urlon,lllat,urlat]
ax.set_extent(extent)

reader = shpreader.Reader("singapore_shapefile")
shape_feature = ShapelyFeature(reader.geometries(), ccrs.PlateCarree(), facecolor="w",
                               edgecolor='black', lw=1)
ax.add_feature(shape_feature)

plt.savefig("singapore.png")

这是输出图。