Nike+ GPS with iPhone 3GS on treadmill question

[wineandcarbs]

Hi all,

I am using the Nike+ GPS app with my 3GS on the treadmill. When I am walking on the treadmill (warming up) the mileage seems pretty bang on or not far off. However, once I start running the Nike+ GPS app starts to show my mileage as further than the treadmill does. At the end of the run it is showing my distance covered as almost 1/4 mile further than the treadmill does.

Which would you assume is most accurate? I suppose while on the treadmill even though it's at a set pace you could be running faster or slower (you might be always toward the back of the treadmill or running faster and toward the front... or does that make no sense? LOL.)

I'm just wondering which you would assume is correct if keeping track of your mileage. TIA.

 

[robbieduncan]

The treadmill knows exactly how far it has moved (or it should do). The Nike+ is guessing based off a stride length.

 

[wineandcarbs]

The treadmill knows exactly how far it has moved (or it should do). The Nike+ is guessing based off a stride length.

Thank you. So would you go w/ the treadmill's measurements then? I'd rather underestimate my mileage than overestimate.

 

[robbieduncan]

Thank you. So would you go w/ the treadmill's measurements then? I'd rather underestimate my mileage than overestimate.

Yep. The treadmill manufacturers know the exact length of the belt. The treadmill can measure very accurately how fast it's moving at all times. It should be 100% accurate.

 

[wineandcarbs]

Yep. The treadmill manufacturers know the exact length of the belt. The treadmill can measure very accurately how fast it's moving at all times. It should be 100% accurate.

Thank you!