Processing gpx file

Using to read and process some information contained in a gpx file

Gpx file is kind of standard file to exchange information between GPS devices and created by a certain GPS devices such as smartphone.

Gpx file always contains info of way points (latitude and longitude) and the time stamps of a track that can be used to calculate a lot of parameters of the track such as average speed, length of the path...

In this program I try to calculate the length of the path that I take between two arbitrary moments t1 and t2.