GeoPandas – Getting Polygon Areas Using GeoPandas

Question

Given a GeoPandas's GeoDataFrame containing a series of polygons, I would like to get the area in km sq of each feature in my list.

This is a pretty common problem, and the usual suggested solution in the past has been to use shapely and pyproj directly (e.g. here and here).

Is there a way to do this in pure GeoPandas?

Answer 1

If the crs of the GeoDataFrame is known (EPSG:4326 unit=degree, here), you don't need Shapely, nor pyproj in your script because GeoPandas uses them).

import geopandas as gpd
test = gpd.read_file("test_wgs84.shp")
print test.crs
test.head(2)

Now copy your GeoDataFrame and change the projection to a Cartesian system (EPSG:3857, unit= m as in the answer of ResMar)

tost = test.copy()
tost= tost.to_crs({'init': 'epsg:3857'})
print tost.crs
tost.head(2)

Now the area in square kilometers

tost["area"] = tost['geometry'].area/ 10**6
tost.head(2)

But the surfaces in the Mercator projection are not correct, so with other projection in meters.

tost= tost.to_crs({'init': 'epsg:32633'})
tost["area"] = tost['geometry'].area/ 10**6
tost.head(2)