Merging overlapping features using Geopandas?

Question

I have a Shapefile with overlapping features. Is there an easy way to merge them with geopandas?

I found a way with shapely, but I would like to do it with geopandas directly.

Answer 1

The GeoDataFrame

import geopandas as gpd
g1 = gpd.GeoDataFrame.from_file("poly_intersect.shp")
g1.shape
(4, 3)

1) You can use the itertools module

a) If you want to merge the intersections of the overlapping polygons

import itertools
geoms = g1['geometry'].tolist()
intersection_iter = gpd.GeoDataFrame(gpd.GeoSeries([poly[0].intersection(poly[1]) for poly in  itertools.combinations(geoms, 2) if poly[0].intersects(poly[1])]), columns=['geometry'])
intersection_iter.to_file("intersection_iter.shp") 

Union

union_iter = intersection_iter.unary_union

b) If you want to merge the intersected polygons change intersection by union (all the polygons overlap in my example)

2) You can use GeoPandas Overlay

a)

auto_inter = gpd.overlay(g1, g1, how='intersection')
auto_inter.shape
(7,4)

The resulting GeoDataframe

GeoPandas add the intersection geometries to the existing geometries, therefore

intersection = auto_inter[4:7]
intersection.to_file("intersection.shp") 

Union

union = intersection.unary_union

b) use gpd.overlay(g1, g1, how='union')

Answer 2

If you want to output a layer of distinct merged overlapping polygons, and not just a single multi-polygon, then after using:

union = intersection.unary_union

you can convert the resulting multi-poly to a GeoSeries:

shapes_series = gpd.GeoSeries([polygon for polygon in union])

or to a GeoDataFrame:

shapes_df = gpd.GeoDataFrame([polygon for polygon in union]).set_geometry(0)