Saturday, May 31, 2014

Changes to the analysis of the GPS accuracy of running watches

I’ve made two changes to my code for analyzing the GPS accuracy of running watches.
  1. My code was using the distance recorded for the first and last point in a lap, which should be the overall distance of the lap. However, for some watches the lap points do not reflect the complete lap, so I’m now using the distance recorded for the lap itself. 
  2. I saw at least one file from the 620 where GPS data was missing for the first couple of miles, even though distance data was recorded. I’m now ignoring those situations as anomalies.
This has a number of impacts
  • The accuracy of some devices improves slightly.
  • The ranking changes slightly, with the Garmin 620 and 10 improving while the Fenix 2 drops below them.
  • My testing of two different 620 watches now shows a greater difference between them. The original 620 now looks poor, but not terrible while the replacement 620 is far worse. This might explain why some people are seeing better GPS accuracy than others from the 620.

Wednesday, May 28, 2014

Comparing the accuracy of a Footpod with GPS

So how does the accuracy of a footpod compare with GPS? You might be surprised, but I've been using a Footpod whenever pace is critical, such as pacing a marathon.

Friday, May 23, 2014

Accuracy of GPS running watches updated

Lots of small changes to my GPS accuracy analysis. I've moved some of the details to subpages for clarity, used deviation from the true value as well as the mean, shown the average pace error, and more. Next up, a comparison with footpod accuracy, the Suunto Ambit2 R, Galaxy S3, plus looking at how GPS satellite position impacts accuracy. 

Tuesday, May 20, 2014

Monday, May 12, 2014

Reflective running gear

I've been buying new reflective gear for the Keys 100 and Badwater and posted my top choices at


Saturday, May 10, 2014

Heat Acclimation Training

I've been asked about my heat training for the Keys 100 and Badwater, so I've updated my Wiki page, adding pictures (and warning) for my heat suit.

Tuesday, May 6, 2014

Running shoe recommendations

I've updated my running shoe recommendations, focusing on the Sketchers GOrun Ultra. I added more detailed discussion of the issues I've found, with extra pictures. I added a lot more dissection pictures of other shoes, including a comparison of the Altra Olympus and the Hokas to highlight the differences in the sole.