Originally Posted by Iride01

If you had simply added a speed sensor (wheel sensor) and your GPS device is able to use that info, then it'll fix your issue. Every cycling GPS I've looked at defaults to using the wheel sensor info when available. Of course if a phone app is your GPS device, then there have been exceptions.

With your Sigma that I guess is a non GPS device, you've solved that for when you are on the bike because I assume it's one that has some sort of wheel sensor. But your data uploaded to Strava and other places via what ever GPS device you use won't have that info. But they could if you'd get a wheel sensor that is compatible with your GPS device.