Frustrated (Nike+ Fail)

I'm feeling rather frustrated today.

I've been wondering how accurate my nike+ shoe pod is. I run the same route all of the time and every time I do 5K, I seem to turn around at a different point. So I headed off to a nearby track to calibrate my nike+. Going there, Nike+ says I've gone 2.03K at a pace of 7:26min/km. I run around the track once, walk around the track once to calibrate. Coming back following the same route - distance = 1.73km at a pace of 8:23min/km. I'm thinking nike+ is on crack. So I pull up mapmyrun.com to check the distance =1.79km. So calibrated run is more accurate, ok.

I check a couple of websites where you enter in the distance and the time it took - pace is 8:04min/km. So its quite possible that my wonderful running breakthrough from last week was just my nike+ being inaccurate. And the 8K run I did on the week-end was really 7km.

I'm feeling pretty frustrated as I thought I had made all sorts of progress. I'm glad that I found this out now and not at my 10K in two weeks. Would have been an unwelcome surprise that A - I'm running slower than I think and B - that 10K is further than any of my training runs.

I'm trying to tell myself that I shouldn't be concerned with how fast I'm going. That three years ago I was in so much pain from my arthritis that I could barely walk. That when I started last year, I could barely do 3km. But its still frustrating that I haven't improved my time at all since last year. Ah well, at least I have a more accurate start point now.