Both devices record at the same time, but the user wants to merge the heart rate data with the ride data. For example, a user has a Wahoo device that records heart rate, and TCX output from their indoor trainer. The other thing this tool can do is combine overlapping files. In this scenario, the user uploads both ride files, and then combines them into one, single GPS file.
The first is if their GPS dies during a ride, and they start another activity (on their phone, for example). There are two ways that people commonly combine files. This tool will allow you to take GPX, TCX, or FIT files and combine them into one single file for upload to Strava.
