Workout App (Outdoor Cycling) vs MapMyRide App ? Watch Series 0

[anon(631408)]

I think that was the best title I could come up with for my issue. I use MapMyRide and I start the workout app Outdoor Cycling. I did this to see if the mileage shows up to be the same. I have my phone with me. I start MayMyRide on my iPhone 7 and then start the Outdoor Cycling workout on my watch. In my view they are both are using the iPhone's GPS but EVERY TIME the mileage is off. Why?
Examples:
AW - 25.63 miles / MMR - 25.82 miles (-.19)
AW - 25.75 miles / MMR - 25.95 miles (-.20)
AW - 52.28 miles / MMR - 52.71 miles (-.43)

Those are my last 3 rides and over the course of 61 rides this year:
AW 2050.02 miles / MMR - 2189.72 miles (-139.7)

isn't it the same GPS?

This is very confusing to me.

Any thoughts?

 

[kch50428]

The accuracy of the position fix one thing... The differences in how often each app is sampling your location is another...between those two, it could account for the discrepancy.