Why Is My Geopy Distance Calculation Inaccurate?

Calculating Distance Between Points Using Latitude and Longitude

In an attempt to implement the formula for calculating distances based on latitude and longitude, users have encountered inconsistencies with their code. The given formula shows promising results in an applet, but applying the same formula in Python code yields incorrect distances.

The reason behind this discrepancy lies in the deprecated nature of the Vincenty distance calculation method. In GeoPy versions prior to 1.13, the Vincenty distance was the default method for calculating distances, while versions 1.13 and above have introduced geopy.distance.distance() as the preferred method.

The Vincenty distance method utilizes ellipsoidal models, such as WGS-84, which provide more accurate results compared to the haversine formula that assumes a spherical Earth. This assumption can lead to errors of up to 0.5%.

To calculate distances accurately, users should replace their implementation of the Vincenty distance formula with the following code:

import geopy.distance

coords_1 = (52.2296756, 21.0122287)
coords_2 = (52.406374, 16.9251681)

print(geopy.distance.geodesic(coords_1, coords_2).km)

This code will calculate the distance between the two points using the more accurate ellipsoidal model and return the result in kilometers.

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