How can I calibrate the Apple Watch 6 manually so that the indoor running estimation gets more accurate ? I run a little faster than average, so it underestimates about 300 meters per kilometer. That sucks. I have all the settings correct for using outdoor runs as a data foundation for calibration (I have a lot of runs), but it doesn't make much of a difference. Maybe I move a little bit differently on the treadmill and obtain a more stable posture with more of a constant speed with flat and nice elevation compared to a more up and down all the time environment outside. I don't know. Is it possible to do this manually now ? (I know it is not possible on Apple Watch 2, but I was sure that it was going to be possible now ... It's 2020 ... duh!). Help.
There is no manual calibration. You can hope that your indoor stride matches your outdoor stride and use it to refine the step lengths.
The system calculates stride length based on GPS and pace, so if you’re is off, resetting the existing calibration and repeating the outdoor calibration in straight line / flat conditions might be worthwhile.