GPS Jobbies

[El Gordo]

They do occasionally fail, particularly in city centres, surrounded by high buildings, or under thick tree cover.

However, the GPS works out how far you've gone by measuring a straight line from the last reading. This is fine if you've travelled in a straight line since the point where the signal is lost. Not so good if you've been zig-zagging round.

The reality is that the great majority of GPS failures are short-lived, so you don't get much distortion in the figures. Most running places don't cause any problems. If people do normally run next to tall buildings, or through thick forest, I suppose the best advice may be not to use a GPS at all. Find some other measuring device.

As for their accuracy, this can be tested pretty easily by using them in races, or for distances that you know for sure are accurate (like on a track). Bath Half marathon, mine said 13.31 but Nigel's, I seem to recall, was 13.13. Copenhagen marathon, mine said 26.7. Given it was a really mazy urban marathon, I'd say that is acceptable. I used it for a 10K where it came out at exactly 6.2.

So the accuracy is pretty good on the whole.

I'd have thought a HRM was accurate as it's directly measuring your heartbeat. But this can be tested easily enough I guess by just taking your pulse, though perhaps not easy while actually running.

What a helpful answer, eh?