Extreme smoothing of climb data in imported generic GPX files

For those in the future seeing same issue. My conclusion is, that if the GPX / TCX data being imported is not stamped with a Garmin device as recording it, Garmin Connect applies very aggressive averaging on elevation data, resulting in 30-40% of total climb disappearing when doing MTB riding.

To work around this with 1000+ activities over 15 years I have amassed in SportTracks, I deleted all the already imported activities in Garmin Connect (yes > 1000..., each is two clicks to delete, there's also no bulk delete). I then found an old copy of the Export2TCX plugin to SportTracks 3.1, then I went ahead and exported all activities again to TCX instead of GPX, which also brought over heart rate, kadence and power (where I had this) as part of the data - so much better data. This resulted in about 30 files, as Garmin Connect will also not reliably import data files over 25MB in size.

Importing this data still gives the same smoothing issue. So to solve that, I used a text/replace tool that can replace blocks of text in ASCII/ANSI files (TCX files are just ASCII XML files), and in the right places between each "</lap> </activity>" pair, I inserted the right XML text to signify which Garmin device (530 or 705) was used to record the data, to not have Garmin Connect smooth out data. And the modified TCX files were then imported. To get all data tagged to the right bicycle equipment, the files imported were grouped by bicycle, and before each run I modified the bicycle to be used as default for new data, to get all this correctly tagged also.

After importing all data, I had to go through all the 1000 activities to retag them also to either Mountainbike or Biking on Road as right type of activity - there was no way to trigger this during import (e.g. default activity type) or as bulk edit. So another few thousand clicks.

Finally all data is as needed - however Garmin has not made it easy in any way to move over your life history of training activities, there's so many simple things that could be done to ease this, like bulk edits, better filters and ability to set defaults.

If you haven't noticed, Garmin Connect is also a lock-in on the data, they go through all possible steps to prevent you to migrate off again... Now when connecting to other services, they only allow to sync over the last month of data, and there's no bulk export function at all. Wonder what the various trials and rulings at EU level of Right to Your Own Data would think about that. I'm saving my TCX exports that I've already done to cover that future scenario, but as new data comes in from the Garmin devices (actually I already have 2 years of that), I can only get it off the Garmin platform again by exporting each activity individually and manually.