I use two apps: Strava and Map My Ride. I also have a Cateye CC-MC200W.

I'm interested in finding out why there's a small discrepancy on the distance the three units record.
For example today on a ride I saw the following distances:
Cateye 32.8km
Strava 33.45
Map My Ride 33.05
As the two Apps both use GPS, I would have thought the distance would be exactly the same, although I know it's only around 1 2-%.
Sometime my Cateye records slightly higher kilometres than the two Apps, so it's not always consistent.

Can anyone enlighten me?