Distance between two GPS points with altitude

[Informatix]

under the latitudes of France or Belgium (~45°), it is usual to take 6371000 for the radius of the earth instead of 6378, which is the radius of the earth at the equator. (https://fr.wikipedia.org/wiki/Rayon_de_la_Terre)

It's even better to compute the right radius with the code provided above (EarthRadiusInMeters).

 

[sorex]

Yes, my mistake. I thought that the Earth curvature had a significant impact. It is not the case for distances < 100 km.

I bet it does when you track a distance like riding the mont Ventoux.

1km billiard or 1km at 10-15% will be different in lenght on a flat map.

 

[Informatix]

I bet it does when you track a distance like riding the mont Ventoux.

1km billiard or 1km at 10-15% will be different in lenght on a flat map.

You make a confusion between altitude and ground curvature.
There's no doubt that altitude can change things a lot. That's why I was looking for a formula taking the altitude into account.

 

[Informatix]

I can confirm that the computation in post #14 is extremely accurate (centimetric accuracy). I checked with the accurate computations made by a professional tool.