3% difference speed sensor vs GPS I'm using the Wahoo ELEMNT BOLT with RPM speed sensor. First few rides with my dad I noticed my measured distance was about 2-3% off from his, I used the standard 2.096m size of my wheel (700x23C). He uses the Polar V650 which measures it with GPS. When I let Strava recalculate the distance is also has this difference. 

After this I started using the auto-calibrate feature but this error still holds, not much has changed. I also did a rollout test where my circumference come to be around 2.093m. This difference however only accounts towards a 100m difference in distance. Nowhere near the difference that the GPS units calculate. 

Anyone of you have any experience with these kind of sensors and data discrepancy? GPS is quite trustworthy when looking at the total distance so I'm not sure what to trust.
It may not have to do with sensors or wheel diameter. My gf and I go on rides together both using Strava via phone app. Every time, without fail, the data will claim she rode about .15 per mile more than I, even though we stayed together during the ride. I've tried it with my Garmin and get similar results. I think GPS technology is just jankier than we perceive it to be. I have looked closely at some of the map data after rides and often, my path on the map looks like a squiggly line when I know I wasn't swerving THAT much. Gps is just not perfectly accurate. If your wheel and your dad's wheel are the same diameter and you get different results, this is probably why.