在 python 的 cartopy 中绘制经度、纬度和半径 (km) 的圆

Question

#!/usr/bin/env python

import os, sys
import pandas as pd
import cartopy
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import shapely.geometry as sgeom
import numpy as np
from cartopy.geodesic import Geodesic


if __name__ == '__main__':

    stn = pd.read_csv('obs_station.csv')
    gd = Geodesic()

    lcc = ccrs.LambertConformal(central_longitude=126., central_latitude=38.)
    fig = plt.figure(figsize=(7,7))
    ax = fig.add_subplot(111, projection=lcc)
    ax.coastlines(resolution='50m')
    geoms = []
    for lon, lat in zip(stn['longitude'], stn['latitude']):
        cp = gd.circle(lon=lon, lat=lat, radius=250000.)
        geoms.append(sgeom.Polygon(cp))
    ax.add_geometries(geoms, crs=lcc, edgecolor='r')
    ax.set_extent([120., 133., 30., 43.])
    plt.show()

文件'obs_station.csv'包含多个经纬度坐标。

使用上面的代码，我尝试绘制具有特定半径（250 公里）的圆。但是，地图上没有任何东西，如下所示。只显示有海岸线的地图。

不知道是什么问题。请帮忙

Result

Answer 1

由于您在 .add_geometries() 语句中指定的坐标转换错误，您没有得到圆图。

为了正确起见，假设我使用这个数据文件： 'obs_station.csv':

longitude,latitude
127.603897,36.932988
126.505337,38.555939

以及修改后的代码：-

#import os, sys
import pandas as pd
import cartopy
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import shapely.geometry as sgeom
import numpy as np
from cartopy.geodesic import Geodesic

if __name__ == '__main__':

    stn = pd.read_csv('obs_station.csv')
    gd = Geodesic()

    # This is long-lat coordinate system for use in ..
    # .. coordinate transformation options
    src_crs = ccrs.PlateCarree()

    lcc = ccrs.LambertConformal(central_longitude=126., central_latitude=38.)
    fig = plt.figure(figsize=(7,7))
    ax = fig.add_subplot(111, projection=lcc)
    ax.coastlines(resolution='50m')
    geoms = []
    for lon, lat in zip(stn['longitude'], stn['latitude']):
        cp = gd.circle(lon=lon, lat=lat, radius=250000.)

        #x,y = lcc.transform_point(lon, lat, src_crs)
        #cp = gd.circle(lon=x, lat=y, radius=250000.)
        geoms.append(sgeom.Polygon(cp))

    # Note the specification of coordinate transformation, using the
    # .. correct parameter:  crs=src_crs
    ax.add_geometries(geoms, crs=src_crs, edgecolor='r', alpha=0.5)
    ax.set_extent([120., 133., 30., 43.])

    plt.show()

输出：

总之，您的代码行：

ax.add_geometries(geoms, crs=lcc, edgecolor='r')

需要正确的 CRS。正确的 CRS 是

ccrs.PlateCarree()

在 python 的 cartopy 中绘制经度、纬度和半径 (km) 的圆

Draw circle with longitude, latitude and radius (km) in cartopy of python

python

geometry

cartopy