How to calculate the area of a polygon on the earth's surface using python?

Question

The title basically says it all. I need to calculate the area inside a polygon on the Earth\'s surface using Python. Calculating area enclosed by arbitrary polygon on Earth&

Answer 1

Here is a Python 3 implementation where the function would take a list of tuple-pairs of lats and longs and would return the area enclosed in the projected polygon.It uses pyproj to project the coordinates and then Shapely to find the area of any projected polygon

def calc_area(lis_lats_lons):

import numpy as np
from pyproj import Proj
from shapely.geometry import shape


lons, lats = zip(*lis_lats_lons)
ll = list(set(lats))[::-1]
var = []
for i in range(len(ll)):
    var.append('lat_' + str(i+1))
st = ""
for v, l in zip(var,ll):
    st = st + str(v) + "=" + str(l) +" "+ "+"
st = st +"lat_0="+ str(np.mean(ll)) + " "+ "+" + "lon_0" +"=" + str(np.mean(lons))
tx = "+proj=aea +" + st
pa = Proj(tx)

x, y = pa(lons, lats)
cop = {"type": "Polygon", "coordinates": [zip(x, y)]}

return shape(cop).area 

For a sample set of lats/longs, it gives an area value close to the surveyed approximation value

calc_area(lis_lats_lons = [(-102.05, 41.0),
 (-102.05, 37.0),
 (-109.05, 37.0),
 (-109.05, 41.0)])

Which outputs an area of 268952044107.4342 Sq. Mts.