WHY YOUR GPS WATCH MAY NOT ALWAYS BE ACCURATE

Running is such a simple activity to get involved in. All you need is a pair of runners, maybe even a watch and you’re all good to go.
It’s all so simple until the data your trusty watch shows back to you, doesn’t quite add up. Maybe your watch data doesn’t match your Strava account, maybe there’s a kilometre in the middle that is strangely twice as fast or the all time classic, the watch doesn’t record 400 metres even though you’ve done a single lap of a legit 400m athletics track. Keep reading for a few reasons why this happens and what you can do about it.

How does a GPS watch actually work
Your watch uses a GPS (Global Positioning System) to track your distance and speed.
Which means that your watch is constantly pinging satellites to get data points to assess how far and how quickly you have moved. So technically, a GPS doesn’t know where you are all the time, it just knows where you are at certain points in time and assumes the bits in between.
This is perfectly illustrated if you run around an oval or athletics track and after uploading the GPS image, you can zoom in and see a series of small straight lines, as opposed to neat curves.
Which leads me to my first point…

Why a GPS watch isn’t accurate on an athletics track;
You may be running laps of an athletics track which is a standard 400 metres and before you complete 2 ½ laps, your watch beeps to signal 1km. How could this be?
Your watch isn’t recognising the neat curves you’re running around each lap and just thinks you’re running in a series of straight lines which means your watch thinks you’re running less than you actually are.
Typically your watch may robbing you of 10-15 metres per lap.

For the sake of the athletics track though, let’s bring this back to common sense.
We know 1 lap = 400 metres, therefore 2 ½ laps = 1km, 7 ½ = 3km and 12 ½ = 5km there’s no arguments with that, even if your watch is telling you that you’ve done 5km after 12 laps, ignore it and get that extra half lap done!

If you’re looking to run the most accurate course possible using your GPS watch, I’d stick to relatively straight out and backs or loops with limited turning and corners. So once again, the next time you run a major 10km event and your watch reads 10.2km, you’ve probably legitimately run 10km due your watch cutting all the turns and corners.

Other reasons your watch may not be working
Don’t forget it’s data is based on satellite feedback, so simple interference like running through forests or tunnels can cause a dropout and sometimes it’s just a good old fashioned glitch with the technology - maybe your device is just getting old.

How to fix it
Your watch’s GPS system is a form of software which needs a regular update just like your iPhone does. For most brands and watches, this would run in the background but sometimes you need to check in the settings or plug it into the computer to get things rolling. Doing a quick google ‘how to update X GPS watch brand/model’ won’t hurt if you get stuck.

I hope you haven’t finished reading this ready to burn your watch thinking ‘what’s the point if it’s not even accurate’. Because it is accurate most of the time.
This will just help you find a sense of calm next time things don’t quite add up post run.