## Toolbox: Get Bounding Box Polygon and centroid of a point cloud in Python

August 15, 2022

Let’s assume that we have a set of points, for example:

And we would like to get their **Bounding Box** and its **centroid**. How do we achieve it? We can use `shapely`

and `GeoPandas`

packages for it!

from typing import Union import geopandas as gpd from shapely.geometry import Polygon def points_to_bounding_box(points: Union[gpd.GeoSeries, gpd.GeoDataFrame]): """ Function transform a set of points into a Polygon with bounding box. Parameters ---------- points : gpd.GeoSeries Returns ------- bounding_box : Polygon """ bounds = points.total_bounds x_min, y_min, x_max, y_max = bounds polygon_tuples = [ (x_min, y_min), (x_max, y_min), (x_max, y_max), (x_min, y_max) ] polygon = Polygon(polygon_tuples) return polygon poly = points_to_bounding_box(centroids) print(poly)

POLYGON ((1305267.3457557156 210560.55098878054, 2198938.029283345 210560.55098878054, 2198938.029283345 1163583.8925663661, 1305267.3457557156 1163583.8925663661, 1305267.3457557156 210560.55098878054))

If we want to get a centroid, then we can use the `centroid`

attribute of `Polygon`

structure:

print(poly.centroid)

POINT (1752102.6875195305 687072.2217775733)

Plotting all together can be a little bit tricky – we must change simple geometries into `GeoSeries`

objects, and then we can plot our output:

bb = gpd.GeoSeries(poly) bb.set_crs(crs=centroids.crs) # Here we must set CRS of our baseline set of points! cent = bb.centroid # We can generate centroid from GeoPandas GeoSeries object # Plot base = bb.plot(color='white', edgecolor='gray', figsize=(12, 10)) centroids.plot(ax=base, marker='o', color='red', markersize=10); cent.plot(ax=base, marker='x', color='green', markersize=20) plt.show()

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