GPS Jobbies

[Nigel]

Go for the 201, SP. It's worth it so you can download the data.

The accuracy is pretty good. One regular sortalong run of mine has varied from 7.42 to 7.57 miles - plus/minus 1% or so.

In London, I gained an extra half mile in the early stages of the race, perhaps because it was difficult to run a tight line amidst the crowds.

Then I lost this extra distance in a short period around Canary Wharf Tower, where the Forerunner had me jumping temporarily to 2 500'. Since the only Superman-type leaps that day were a couple of brief dashes for the bushes (visible as spikes in the pace plot), I'd guess that was a multiple reflection problem from the high buildings. The final mileage recorded was 26.18 miles.

You can see the faster first 3 miles, all downhill, then a more or less even-paced section before the loss of signal at Canary Wharf around 17 miles. After that my performance steadily deteriorated beyond Mile 20, before a short but emotional final sprint up The Mall to the finish.

In Blackpool, there were no such problems with crowds, bushes or buildings, and the final distance was 26.21 miles. Don't worry, I ran the extra 17.6 yards anyway, just in case.....