Thanks for the link, very useful!
However, it does not make sense for me yet.
Since both data (TGP data and GPX file) came from the same source, I don't understand why they're different.
I understand that the watch itself may use other variables to calculate distance, but then all data is sent to TGP.
Therefore, TGP has all information, and it shows as the watch does.
Afterwards, when you save the data as GPX, you get the difference.
That's unclear for me.
Even creating a straight route in google maps (which means, no deviation in the same street) is larger than the distance reported in the watch. It should be the other way around, shouldn't it? Considering that with GPS we have more deviation..