Running track test: How accurately does the sports watch measure?

Suddenly I'm world class. As I look at the Amazfit Bip on my wrist during my run, I can hardly believe my luck. I've just eaten a big pizza and now I'm on course for a record with a lump in my stomach. STOP THE COUNT, STOP THE COUNT, I think. The numbers are lying so beautifully right now. If Xiaomi's incorruptible technology is anything to go by, I've just run 8.51 kilometres at an average speed of 3'01''. With just under 33 kilometres to go, Viktor Röthlin's marathon best time is on the line. I would finish in 2:07:29. The last time I ran a kilometre at this pace, I was 18 and lay gasping in the grass afterwards. Eight was never an option. Until today, powered by homemade pizza.

I have a relaxed relationship with jogging and don't run to chase personal best times. It's part of it, clears your head and is fun, especially when it's over and the good feeling sets in afterwards. I run, the clock runs with me. I've already expressed my indifference by buying a cheap one with an extremely long battery life.

Sports watches + Smartwatches

Amazfit Bip

45 mm, Plastic, One size

24

Sports watches + Smartwatches

Amazfit Bip

45 mm, Plastic, One size

24

I take a look at my heart rate. Afterwards, the collected values are data rubbish for me, which the Chinese secret service can interpret for all I care. I already noticed that the measurements are not beyond all doubt when comparing distances with my neighbour, whose iPhone spit out a different distance each time. Acute suspicion of fake news is nothing new in connection with sports watches and fitness trackers.

The problem is that we usually believe the data and don't give it a second thought. GPS navigates us through the world, knows the best routes and exact distances. Hey, GPS! Where were you when I was in the forest? The weather was neither good nor bad, the canopy was no longer particularly dense. Normally, there should be more than enough satellites available to determine my position.

So what was the problem? In which parallel universe was my clone travelling? Why does my running route look like it was scribbled on the screen by a two-year-old? I swear that - apart from the pizza - I was sober and could only be found in a few of these places.

This raises questions. Is Q behind this? Where was Bill Gates at the time? And why did the Mi Fit app support team remain silent in response to my innocent enquiry about how this could have happened? The truth, that much seems clear, is something I have to find out for myself.

Multipath error

In order to determine my position, my GPS device needs the signal from at least four satellites. There are usually a few more. The transit times of the various signals can be used to precisely determine my current position. However, it can happen that the signals are deflected. High buildings or natural obstacles reflect them so that they reach my receiver in different ways. It reacts in a correspondingly confused manner and records wild jumps in position. This so-called multipath error is the most common reason for conspicuous errors. A particularly good example of this is probably responsible for my performance explosion. However, nothing comparable has ever happened to me on this route. According to gps.gov, radio interference, large solar storms, satellite maintenance or unsuitable receivers affect accuracy far less frequently. Although your smartwatch will never be completely accurate.

GPS drift

GPS drift is the distance between your location and what your GPS receiver thinks it is. On gps.gov it says that a smartphone is usually accurate to 4.9 metres. Garmin speaks of around three metres for its outdoor watches. This means that you may be located slightly to the left or right of your actual running route and adds up to the measurement error of your smartwatch. Even a dense canopy of leaves in the forest can cause the accuracy to decrease. If the signal is lost for a short time, your device draws a straight line between the last known location and the new position and calculates this distance. The worst thing from this perspective is a trail run with mountains, trees and tight bends. If you want to rely on your watch's data, it's best to run straight ahead in the open air. Or on the track. That's what I did with my Amazfit Bip.

The running track test

A clear November morning, nothing but a steel blue sky above me. There are no excuses, the conditions don't get any better. I'm on the time-honoured Ligustrum circuit and intend to run 5000 metres to find out just how accurate the Amazfit Bip is. One lap is 250 metres. At first I'm still impressed, my watch records the first few laps relatively accurately. As time goes on, however, it becomes clear that it is crediting me with a few extra metres. If it had my way, I wouldn't even have to run half the last lap. When a vibration on my wrist signals the fifth kilometre, I have just come out of the first bend. At the finish line, after five real kilometres, it shows exactly 5.14 kilometres. It's easy to see why when I zoom into the recording.

The lap then appears quite angular. Individual positions stick out and give me an extra 140 metres. Plus 2.8 per cent. Not actually that bad, is it? At least I now know that the Amazfit Bip tends to record too much. I can live with that. But I also don't organise my training plan according to the data from this watch. I don't compete online with others who might get more metres as a gift. To claim that sports watches are accurate would really be presumptuous.

How is it with you? What experiences have you had with the accuracy of your sports watch? Please leave a comment below.