Is there something wrong with my GPS unit? According to my watch, my pace swings wildly from 5:30 to 8:30 m/min during my daily runs that average between 6-10 miles. I feel like I'm putting out a consistent effort throughout my runs; however, I tend to run on very hilly terrain.
I'm not sure if GPS watches compensate for this... but if you think about it, maybe the GPS systems think it's over a flat surface. So maybe it thinks that you're going slower than you actually are if you're going uphill (because you realistically are running further) and vice versa for downhill.
With a 10% grade (really steep), the angle you are running is such that it does not add significant distance. That is 4.5 degrees. One mile horizontally at 10% grade is 1.005 actual miles. Only an extra 26 feet traveled.
45 degrees is a 100% grade. That means you go up one unit for every one unit that you go across. Even at 100% grade, one mile horizontally is square root of 2 actual miles, or 1.4.
trash the watch and don't worry a boutit
Thanks for your responses. My GPS unit measures elevation, so I'm relatively confident that it is compensating for the extra distance resulting from running hills (however small that may be). My friend has a similar GPS device and he finds it always records a consistent pace over approx 10 mile distances run on flat terrain.
Most likely it is set to current pace instead of average pace. Double check the settings and change if need be.