I really hesitate to post this, but it's a general question based on my observations. For the past three months or so, I have been training with the Nike+ Run Club application on my iPhone -- I wanted to make sure that I stayed within the 16 minute mile cut off. I used the app on a couple of runs, including a 15K here in Port Orange, FL, and it seemed pretty accurate. Then came the Wine and Dine Two Course Challenge 10K on November 4. I clicked the "Start" button in the Nike app as I crossed the starting line. The app announced I was at the one mile point about 90 feet away from the one mile marker. That difference continued throughout the course -- the distance increased and I was always "ahead" on my run, and when all was said and done, the app claimed that I ran 6.48 miles, not 6.2 (see attached picture) My pace, per the app, was 14'09, Disney reported it at over 15 minutes. For the half marathon, the second day, it was even worse -- every Nike milepost was further and further from the Disney sign, to the point that for the 11th, 12th and 13th mile, the Disney sign wasn't even in sight and it took minutes to finally catch up to it. And, once again, my phone app reported my pace at less than 15 minutes per mile, Disney showed me in at 15:33/mile After that, I figured that there was a problem with the Nike+ Run Club app, because I figured that Disney would make every effort to be accurate, and they most certainly wouldn't make their courses LONGER than they should be, because they want people out of the parks, asap. I registered a complaint with Nike. Fast forward to the next weekend, and I'm running a 5K in Gainesville. I click the "Start" button as I cross the line and, as I cross the finish line, the Nike app tells me that I'm done with my 5K. So, pretty good accuracy, out of Disney. Totally out of accuracy, on two RunDisney runs. Do you have any data to add to this, either Nike being right and Disney being wrong, or the other way around? I'd really like to know, and I'm sure that Nike would like to know, and RunDisney would like to know. One would think that there is a standard mile, and that both Nike and Disney use that standard mile, but my personal experience is that this isn't the case. Who's right?