使用 Cartopy 添加网格线

Question

我正在尝试将网格线添加到我使用 Cartopy 制作的地图中，但是，当我使用来自 cartopy 文档的示例代码时，它没有显示我想要的内容，我不知道如何操纵它来做到这一点。

def plotMap():

    proj = ccrs.Mercator(central_longitude=180, min_latitude=15, 
    max_latitude=55)

    fig, ax = plt.subplots(subplot_kw=dict(projection=proj), figsize=(12,12))

    ax.set_extent([255 ,115, 0, 60], crs=ccrs.PlateCarree())

    ax.add_feature(cfeature.LAND, facecolor='0.3')
    ax.add_feature(cfeature.LAKES, alpha=0.9)  
    ax.add_feature(cfeature.BORDERS, zorder=10)
    ax.add_feature(cfeature.COASTLINE, zorder=10)


    #(http://www.naturalearthdata.com/features/)
    states_provinces = cfeature.NaturalEarthFeature(
            category='cultural',  name='admin_1_states_provinces_lines',
            scale='50m', facecolor='none')
    ax.add_feature(states_provinces, edgecolor='black', zorder=10)

    #ax.gridlines(xlocs=grids_ma, ylocs=np.arange(-80,90,20), zorder=21, 
    draw_labels=True ) 
    ax.gridlines(crs=ccrs.PlateCarree(), linewidth=2, color='black', 
    draw_labels=True, alpha=0.5, linestyle='--')
    ax.xlabels_top = False
    ax.ylabels_left = False
    ax.ylabels_right=True
    ax.xlines = True
    ax.xlocator = mticker.FixedLocator([-160, -140, -120, 120, 140, 160, 180,])
    ax.xformatter = LONGITUDE_FORMATTER
    ax.yformatter = LATITUDE_FORMATTER
    ax.xlabel_style = {'size': 15, 'color': 'gray'}
    ax.xlabel_style = {'color': 'red', 'weight': 'bold'}


    return fig, ax

我附上了输出图片。作为参考，我只希望经度网格线从我域的左侧开始并在右侧结束，最好每 20 度间隔一次。理想情况下，纬度线也相同。 Bad gridline plot

Answer 1

您使用的示例是 this page 底部的示例吗？如果是这样，您正试图在 GeoAxes (ax) 实例上设置应该在 GridLiner (gl) 实例上设置的属性：

import cartopy
import cartopy.crs as ccrs
import cartopy.feature as cfeature
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker

from cartopy.mpl.gridliner import LONGITUDE_FORMATTER, LATITUDE_FORMATTER

def plotMap():    
    proj = ccrs.Mercator(central_longitude=180, min_latitude=15, 
    max_latitude=55)

    fig, ax = plt.subplots(subplot_kw=dict(projection=proj), figsize=(12,12))

    ax.set_extent([255 ,115, 0, 60], crs=ccrs.PlateCarree())

    ax.add_feature(cfeature.LAND, facecolor='0.3')
    ax.add_feature(cfeature.LAKES, alpha=0.9)  
    ax.add_feature(cfeature.BORDERS, zorder=10)
    ax.add_feature(cfeature.COASTLINE, zorder=10)

    states_provinces = cfeature.NaturalEarthFeature(
            category='cultural',  name='admin_1_states_provinces_lines',
            scale='50m', facecolor='none')
    ax.add_feature(states_provinces, edgecolor='black', zorder=10)   

    gl = ax.gridlines(crs=ccrs.PlateCarree(), linewidth=2, color='black', alpha=0.5, linestyle='--', draw_labels=True)
    gl.xlabels_top = False
    gl.ylabels_left = False
    gl.ylabels_right=True
    gl.xlines = True
    gl.xlocator = mticker.FixedLocator([120, 140, 160, 180, -160, -140, -120])
    gl.ylocator = mticker.FixedLocator([0, 20, 40, 60])
    gl.xformatter = LONGITUDE_FORMATTER
    gl.yformatter = LATITUDE_FORMATTER
    gl.xlabel_style = {'color': 'red', 'weight': 'bold'}

这将生成以下地图。 gridliner 似乎无法应对日期变更线。我不知道是否有办法解决这个问题，但上面链接文档的顶部有一条注释说目前已知此 class 存在限制，所以可能没有。

另一种方法是直接使用 matplotlib 设置各种标签及其样式。请注意，您必须将刻度标签与刻度分开设置，否则您将获得对应于墨卡托坐标参考系统的标签：

import cartopy.mpl.ticker as cticker

def plotMap2():
    proj = ccrs.Mercator(central_longitude=180, min_latitude=15, 
    max_latitude=55)

    fig, ax = plt.subplots(subplot_kw=dict(projection=proj), figsize=(12,12))

    ax.set_extent([255 ,115, 0, 60], crs=ccrs.PlateCarree())

    ax.add_feature(cfeature.LAND, facecolor='0.3')
    ax.add_feature(cfeature.LAKES, alpha=0.9)  
    ax.add_feature(cfeature.BORDERS, zorder=10)
    ax.add_feature(cfeature.COASTLINE, zorder=10)

    states_provinces = cfeature.NaturalEarthFeature(
            category='cultural',  name='admin_1_states_provinces_lines',
            scale='50m', facecolor='none')
    ax.add_feature(states_provinces, edgecolor='black', zorder=10)

    ax.set_xticks([120., 140., 160., 180., -160., -140., -120.], crs=ccrs.PlateCarree())
    ax.set_xticklabels([120., 140., 160., 180., -160., -140., -120.], color='red', weight='bold')
    ax.set_yticks([20, 40], crs=ccrs.PlateCarree())
    ax.set_yticklabels([20, 40])
    ax.yaxis.tick_right()

    lon_formatter = cticker.LongitudeFormatter()
    lat_formatter = cticker.LatitudeFormatter()
    ax.xaxis.set_major_formatter(lon_formatter)
    ax.yaxis.set_major_formatter(lat_formatter)
    ax.grid(linewidth=2, color='black', alpha=0.5, linestyle='--')

使用 Cartopy 添加网格线

Adding gridlines using Cartopy

matplotlib

cartopy