使用geopandas和matplotlib绘制地图

问题描述

我有一个小型的csv，具有来自英国伯明翰的6个坐标.我用熊猫阅读了csv，然后将其转换为GeoPandas DataFrame，并使用Shapely Points更改了我的纬度和经度列.我现在正在尝试绘制我的GeoDataframe，我所能看到的就是要点.如何获得伯明翰地图?一个很好的有关GeoPandas的文档来源也将受到高度赞赏.

I have small csv that has 6 coordinates from Birmingham England. I read the csv with pandas then transformed it into GeoPandas DataFrame changing my latitude and longitude columns with Shapely Points. I am now trying to plot my GeoDataframe and all I can see are the points. How do I get the Birmingham map represented as well? A good documentation source on GeoPandas would be strongly appreciated too.

from shapely.geometry import Point
import geopandas as gpd
import pandas as pd

df = pd.read_csv('SiteLocation.csv')
df['Coordinates'] = list(zip(df.LONG, df.LAT))
df['Coordinates'] = df['Coordinates'].apply(Point)
# Building the GeoDataframe
geo_df = gpd.GeoDataFrame(df, geometry='Coordinates')
geo_df.plot()

推荐答案

GeoPandas文档包含有关如何向地图添加背景的示例( https://geopandas.readthedocs.io/en/latest/gallery/plotting_basemap_background.html )，下面将对此进行详细说明.

The GeoPandas documentation contains an example on how to add a background to a map (https://geopandas.readthedocs.io/en/latest/gallery/plotting_basemap_background.html), which is explained in more detail below.

您将不得不处理瓷砖，即通过网络投放的(png)图像服务器，URL类似

You will have to deal with tiles, that are (png) images served through a web server, with a URL like

geopandas的文档显示了如何将图块设置为绘图的背景，如何获取正确的图块以及完成空间同步等所有其他原本困难的工作...

And geopandas's doc shows how to set tiles as backgrounds for your plots, fetching the correct ones and doing all the otherwise difficult job of spatial syncing, etc...

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安装

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Installation

假设已经安装了GeoPandas，则还需要 contextily 软件包.如果您在Windows下，则可能要看一下如何进行上下文安装?

Assuming GeoPandas is already installed, you need the contextily package in addition. If you are under windows, you may want to pick a look at How to install Contextily?

用例

Use case

创建一个python脚本，然后定义 上下文帮助功能

Create a python script and define the contextily helper function

import contextily as ctx

def add_basemap(ax, zoom, url='http://tile.stamen.com/terrain/tileZ/tileX/tileY.png'):
    xmin, xmax, ymin, ymax = ax.axis()
    basemap, extent = ctx.bounds2img(xmin, ymin, xmax, ymax, zoom=zoom, url=url)
    ax.imshow(basemap, extent=extent, interpolation='bilinear')
    # restore original x/y limits
    ax.axis((xmin, xmax, ymin, ymax))

玩

import matplotlib.pyplot as plt
from shapely.geometry import Point
import geopandas as gpd
import pandas as pd

# Let's define our raw data, whose epsg is 4326
df = pd.DataFrame({
    'LAT'  :[-22.266415, -20.684157],
    'LONG' :[166.452764, 164.956089],
})
df['coords'] = list(zip(df.LONG, df.LAT))

# ... turn them into geodataframe, and convert our
# epsg into 3857, since web map tiles are typically
# provided as such.
geo_df = gpd.GeoDataFrame(
    df, crs  ={'init': 'epsg:4326'},
    geometry = df['coords'].apply(Point)
).to_crs(epsg=3857)

# ... and make the plot
ax = geo_df.plot(
    figsize= (5, 5),
    alpha  = 1
)
add_basemap(ax, zoom=10)
ax.set_axis_off()
plt.title('Kaledonia : From Hienghène to Nouméa')
plt.show()

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注意:您可以使用zoom来找到地图的高分辨率. :

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Note: you can play with the zoom to find the good resolution for the map. E.g./I.e. :

...，并且此类分辨率隐式要求更改x/y限制.

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