Showing posts with label calibration. Show all posts
Showing posts with label calibration. Show all posts

Saturday, January 22, 2011

Garmin foot pod calibration - one of life's mysteries

Today's run (street): 5 miles

The action of calibrating my Garmin's foot pod is hit or miss. The best way to do it is when you run an exact distance and it calibrates automatically. Another method is to adjust the foot pod based upon a known factor, such as the percentage between what was recorded and what you actually ran. The third way is the worst way and of course it's the one I usually follow because it's also the the easiest. In this case, when I'm consistently over or under recording my distance (compared with Gmaps) I manually compensate by arbitrarily increasing the the index until I get close. Sometimes this works great and the foot pod will report accurately for many runs. Since I often switch the foot pod between pairs of shoes it's usually off by some factor anyway and that's why I Gmap my runs.

Easier said than done
This morning I adjusted the foot pod thinking that a .05% decrease would compensate for over recording would get me to the 1/100ths of a mile accuracy that I often observe. When I went out this morning on the freshly plowed streets I was moving well. Except for on the spots that were still covered with packed snow my pace was fast and my stride was good. I often follow the same exact route for the first mile to gauge whether the Garmin is ahead or behind my real distance. I must have been confused today because I came through the first mile thinking that the foot pod was under recording, when in fact it was probably off by 3% the other way. I'm still fuzzy about when it chirped and where I was when that happened but when I finished my run the recorded distance was .23 miles greater than what I mapped using Gmaps.

I find it hard to believe my calibration was that far off and I have a different theory. Much of the roads were covered with a combination of slush and snow and my form differed greatly when I ran on those sections versus the open pavement.  It's possible that this difference in stride, cadence and lift may have thrown off the foot pod. I won't ever really know but I'm planning to reset the foot pod to 100% index value and start again. If I thought that a GPS watch would be more accurate I'd probably buy the Garmin 210. Most of the time I'd be better off just running with a stop watch and calculating pace later, after I'd Gmapped the route. The only problem with that is when I run the trails or on the treadmill and the foot pod also provides excellent data that I value, including split times and cadence. I guess I'll just keep calibrating and hoping for the best.

Saturday, April 17, 2010

Time to calibrate the FR60

Today's workout (street): 4.17 miles at 8:57/mile

Yesterday's run felt so effortless that I wasn't ready to stop when we reached the end. Business took priority over pleasure but I did feel great for the remainder of the work day. The run itself was work and I felt the effect of all those hills this morning when I woke up. Still, I was anxious to get out for another run. My wife and kids were volunteering at my son's elementary school all morning. I had nothing on the calendar until after lunch so I headed out for my run around 9:00 AM with temperatures in the the high 30's under overcast skies. My Garmin was fairly quiet so I knew I was within pace range although a check of the display showed my pace to be a little slower than it seemed. I stepped it up after the first mile and would periodically surge for 30 seconds to a minute before falling back to my default pace. I was running faster than yesterday's city excursion and I felt the difference. All the same I didn't feel that I was working that hard and the data from my heart rate monitor confirmed it. I felt like I had covered a lot of ground but I ended up only going a little more than four miles. It was just far enough to count as a good workout.

When I finished the run I checked my Garmin and saw it displayed 4.07 miles, averaging 9:10. 9:10 isn't a bad pace and I figured that yesterday's run had wore me out more than I'd thought. I then mapped the exact route using Gmaps and saw that the Garmin under-counted the distance by 2.3%. Adjusting my pace for that variance, my overall average was under 9:00 (8:57) and my splits were 8:54, 8:57, 9:03 and 8:59. Love the FR60! I'm going to try to calibrate it a little closer so I don't have to do so much math. I haven't messed with the calibration adjustment on the FR60 yet. The default accuracy is +/- 3%. It wasn't all that easy to adjust the 50 so I'm hoping the 60's controls are better. My problem with calibration is that I switch my foot pod often between my pairs of street and trail running shoes and every change affects the calibration accuracy. Overall, I'm happy with my recent runs and glad that I've made my way down to the low 9:00's that I was running prior to my pneumonia disruption. I don't know what I'll run tomorrow. The skies are looking ominous but I'm hoping that this passes and that the trails are in good shape by Sunday.

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