CODEWITHSUNDEEP
pythongisgeopandas
Reda S
Reda S

Reputation: 167

Calculating areas of polygons inside other polygons with GeoPandas

I have two GeoSeries:

df1 = gpd.GeoSeries([Polygon([(0,0),     (2,0),   (2,2), (0,2)]),
                     Polygon([(1.5,1.5), (4,2),   (4,4), (2,4)]),
                     Polygon([(1,3.5),   (3,3.5), (1,2.5)]),
                     Polygon([(1,0),     (3,0),   (3,2.5)])])

df2 = gpd.GeoSeries([Polygon([(1,1), (3,1), (3,3), (1,3)]),
                     Polygon([(3,3), (5,3), (5,5), (3,5)]),
                     Polygon([(1,3), (1,5), (3,5), (2,3)]),
                     Polygon([(5,1), (3,1), (3,3), (3,5)])])

plotting this gives :

base = df2.plot()
df1.plot(ax=base, cmap='summer')

enter image description here

How do you calculate the overlapping areas between df1 and df2?

Upvotes: 3

Views: 2517

Answers (2)

swatchai
swatchai

Reputation: 18772

Here is a working code using your data. Read the comments provided with the code for more information.

import geopandas as gpd
from shapely.geometry import Polygon

# use GeoSeries to prepare data
gs1 = gpd.GeoSeries([Polygon([(0,0), (2,0), (2,2), (0,2)]),
                Polygon([(1.5,1.5), (4,2), (4,4), (2,4)]),
                Polygon([(1,3.5),(3,3.5),(1,2.5)]),
                Polygon([(1,0), (3,0), (3,2.5)])])

gs2 = gpd.GeoSeries([Polygon([(1,1), (3,1), (3,3), (1,3)]),
                Polygon([(3,3), (5,3), (5,5), (3,5)]),
                Polygon([(1,3), (1,5), (3,5),(2,3)]),
                Polygon([(5,1), (3,1), (3,3), (3,5)])])

#base = gs2.plot()
#gs1.plot(ax=base, cmap='summer')

# create geoDataFrame from GeoSeries obtained above
df1 = gpd.GeoDataFrame(gs1)
# assign geometry to the geoDataFrame
df1g = df1.rename(columns={0:'geometry'}).set_geometry('geometry')

# similarly, ...
df2 = gpd.GeoDataFrame(gs2)
df2g = df2.rename(columns={0:'geometry'}).set_geometry('geometry')

# perform polygon overlay betw the two geoDataFrames
ov_output = gpd.overlay(df1g, df2g, how="intersection")
ov_output.plot(figsize=(4,4), cmap="Set2")

# Calculating areas of all the resulting polygons
ov_output.geometry.area

Output text, showing calculated areas of the intersected polygons:

0    1.0000
1    1.8000
5    0.2500
9    0.9000
2    0.3500
6    0.5625
3    1.0000
4    1.8500
dtype: float64

And, the resulting plot.

enter image description here

Upvotes: 4

iacob
iacob

Reputation: 24181

You use geopandas.overlay:

gpd.overlay(df1, df2, how="intersection")

Upvotes: 3

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