Calculation of the distance traveled written in gpx. How to implement in Python?

Question

Python

I decided to write a program that displays the distances recorded in gpx, I figured out the parsing. When calculating large discrepancies in the results.
formulas:
r = radius of the Earth in meters = 6378245
x = r * sin(W) * cos(L);
y = r * sin(W) * sin(D);
z = r * cos(W);
Distance between two points on a sphere = sqrt((x1-x2)^2 + (y1-y2)^2 + (z1-z2)^2)

Answer 1

This is called the "Inverse Geodesic Problem".
Here there is a detailed theory and ready-made python scripts for the sphere : Problems on the sphere: inverse geodesic problem . And there is also a good geographiclib that solves these problems on an ellipsoid .