Using a Speed and Distance Device in Different Environments

By Matt Fitzgerald

Different types of run speed and distance devices, and different ways of using them, are more or less accurate than others in different running environments. If you’re a casual runner, these differences, while they do have a measurable effect on accuracy, are not worth worrying about. However, if you’re a serious competitive runner who trains with precise target paces for various workout types and wants the greatest possible degree of accuracy in recorded workout data, these differences need to be accounted for and addressed as well as possible.

The Roads

In normal training on the roads, all of the speed and distance devices from major brands have an acceptable level of accuracy. For example, my Garmin 305 is consistently 99 percent accurate on the roads, which translates to being roughly four seconds per mile off my actual pace.

That said, it’s useful to know exactly how accurate your device is. You can determine your unit’s level of accuracy by using a bike computer to measure off a mile on a stretch of road you frequently run, and then run it to see how your speed and distance device’s measurement compares. Using this method and other similar comparison methods I have found that my Garmin is not really accurate to within +/-1 percent, as you might expect. Rather, it consistently overestimates distance by roughly 1 percent. This knowledge allows me to make a mental correction of the data my device gives me in every road run. For example, it if tells me I ran 18 miles at 6:56 per mile, I know I really ran something closer to 17.82 miles at 7:00 per mile.

Click here to read more in the full article about using a speed and distance device in other environments, including on the track, the treadmill, and in hilly routes.