如何使用 geopandas 或 shapely 提取内部多边形的坐标？

Question

我有一个英国 county/unitary 当局 (UTLA) 的 geojson 文件，我已经使用 geopandas 阅读了该文件。我试图获得每个 UTLA 的匀称多边形，但我运行遇到包含其他 UTLA（即内部多边形）的 UTLA 的问题，例如德比郡。

我正在尝试提取内部多边形的坐标：

import geopandas as gpd

utla_polygons = gpd.read_file('https://opendata.arcgis.com/datasets/244b257482da4778995cf11ff99e9997_0.geojson')

derbs = utla_polygons[utla_polygons['CTYUA21NM']=='Derbyshire']
derbs_int = derbs.explode().geometry.interiors
derbs_int

derbs_int 是我期望的样子，基于 geopandas documentation:

130  0    [LINEARRING (-1.484521649999976 52.96638748100...
dtype: object

但是，当我尝试从 derbs_int 中提取坐标时，出现以下错误：

derbs_int.coords

AttributeError: 'Series' object has no attribute 'coords'

如何提取这些坐标以便使用它们来创建形状优美的多边形？

Answer 1

从多边形中移除内部多边形的一种方法是访问 JSON 并获取多边形元素的第一个环。

from shapely.geometry import shape
import requests

url = 'https://opendata.arcgis.com/datasets/244b257482da4778995cf11ff99e9997_0.geojson'
r = requests.get(url)
data = r.json()
for f in data['features']:
    if f['properties']['CTYUA21NM'] == 'Derbyshire':
        geom = f['geometry']
        if geom.get('type') == 'MultiPolygon':
            print("BEFORE:")
            for p in shape(geom).geoms:
                print(len(p.interiors))
            geom = [g[0] for g in geom['coordinates']]
            geom = shape({
                'type': 'MultiPolygon',
                'coordinates': [geom]
            })
            # geom is a MultiPolygon instance with polygons only having an exterior ring
            print("AFTER:")
            for p in geom.geoms:
                print(len(p.interiors))
        break

输出：

BEFORE:
1
AFTER:
0

0 表示多边形没有内环。

Answer 2

需要系统化。多边形包含多边形，多边形包含内部，内部有坐标

import geopandas as gpd
import requests

res = requests.get(
    "https://opendata.arcgis.com/datasets/244b257482da4778995cf11ff99e9997_0.geojson"
)
gdf = gpd.GeoDataFrame.from_features(res.json()).set_crs("epsg:4326")

gdfd = gdf.loc[gdf["CTYUA21NM"].str.contains("Derbyshire")].copy()

gdfd["geometry"].apply(
    lambda g: [g3.coords for g2 in g.geoms for g3 in g2.interiors]
).explode().explode()

输出

130     (-1.484521649999976, 52.96638748100003)
130     (-1.484809956999925, 52.96630955400008)
130     (-1.484938351999972, 52.96627955300005)
130     (-1.485184568999955, 52.96623118800005)
130      (-1.48530681099993, 52.96621284400004)
                         ...                   
130     (-1.483622200999946, 52.96727346400007)
130     (-1.483387032999929, 52.96689850300004)
130    (-1.483327163999945, 52.966792199000054)
130    (-1.483532068999978, 52.966718497000045)
130     (-1.484521649999976, 52.96638748100003)
Name: geometry, Length: 1587, dtype: object

如何使用 geopandas 或 shapely 提取内部多边形的坐标？

How can I extract the coordinates of an interior polygon using geopandas or shapely?

python

geopandas

shapely

输出