Sunday, May 15, 2011

Garmin FR210 - your mileage may vary

Example of 210 cutting corners, under counting distance
Today's run (street): 3.92 miles

As expected, the rain started last night and continued into the morning. At 7:00 AM I was considering doing an extended elliptical session rather than suffering a soaking run. By 7:30 the rain had slowed to a drizzle and I went outside in hopes of running 30-40 minutes before the next deluge. Yesterday's Stillwell workout was rough, in the best of ways, but I felt no residual effects of it this morning.

It didn't take too long to acquire a signal on the Garmin and I took off after a couple of minutes of dynamic stretching. I still had some pain in my left knee but it wasn't too bad. At this point it's an irritant more than an injury and it usually goes away after a few minutes.  I felt that I was moving fairly well at the beginning but according to the Garmin I was running slightly over 10 min/mile. By now I know the difference between a 9:30 and 10 minute pace and I also know that the Garmin, at best, under-counts my speed by 3%. I didn't worry too much about my pace but I began to pick things up by mile 2.

After verifying my true distance on Gmaps I saw that the Garmin had under-recorded my run by 6.8%. An examination of my route recorded on the 210, using Garmin Training Center, showed the many variances from my actual route that added up to that margin of error. I'm guessing the heavy cloud cover may have interfered with the GPS sampling frequency. I was hoping that this watch would provide a closer margin than -3%, which seems to be the average variance. I'll just expect to have an even greater variance on cloudy days.

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