These watches lie about location. Polish scientists confirm

According to researchers' findings, some watches measure distance to an accuracy of 1 meter and below, but others with an error of even more than 20 meters. They are also not suitable for measuring height, they often don't even know that they are climbing with a human.

3 brands taken under the microscope

Sports watches are equipped with receivers of various satellite systems, which differ, among others: the time system used or the structure of the code emitted by the satellites, which causes differences in the form of delays in signal decoding. When the satellite receiver in your watch incorrectly accounts for the differences between GPS, GLONASS and Galileo, positioning errors may be greater than when using one satellite system.

According to the Naukawpolsce.pl website, scientists from Wrocław have verified the accuracy of sports clocks in terms of satellite positioning relative to precise geodetic receiver. They checked distance measurements on the athletic track and height difference measurements on the observation tower. The research results were published in Measurement. Thanks to this, we can learn the exact models and brands of the checked watches. These are Suunto (5, Ambit3), Garmin (Forerunner 735XT, Forerunner 745, Fenix ​​6, Vivoactive 3 Music, Vivoactive 4s) and Polar (Grit X, M430, Vantage V)

What was the experiment like?

The first stage of the experiment was carried out on a test route approximately 2.7 km long in Wrocław. The route included areas with varying sky visibility.

The reference point was the professional Leica GS18 geodetic receiver. The geodetic receiver uses real-time corrections from the WROC reference GNSS station, guaranteeing positioning accuracy of less than 3 cm and height of less than 5 cm. Sports watches and the receiver were placed on a geodesic pole using an additional frame

– describes prof. Ph.D. engineer Krzysztof Sośnica from the Institute of Geodesy and Geoinformatics of the University of Wrocław.

There were no surprises here. The largest errors occurred in areas surrounded by buildings or trees. In areas with fewer obstacles, the positioning accuracy of the watches was higher. High stability sports watches also showed different positioning accuracy between unobstructed and occluded areas of the horizon.

The researchers confirmed that lower quality sports watches show this difference less clearly. In their opinion, this is due to higher signal noise in the GNSS module of individual devicesresulting in low positioning accuracy even under ideal conditions, unlike more stable sports watches.

Next tests – height and treadmill

The high-altitude experiment was performed on a 36.83 m high steel tower located in Kotowice near Wrocław. Measurements were taken at 13 levels approximately 2.9 meters apart. Height differences were determined using a laser rangefinder. In this way, the researchers provided a reference to the height differences between the different levels of the tower platform. In each GNSS configuration at each tower level, the sports watches were held in place for over 3 min in order to record a similar number of observations at each tower level.

Here too it turned out that watches are not suitable for accurate height measurement. Despite the increase in height, some models showed lower readings at higher levels on the tower. Only two types of sports watches showed an increase in value at each subsequent level, where measurements were made. However, at some levels the differences between their results and the reference were within meters.

The last part of the study – the distance experiment – was carried out on a full-size athletics track in Wrocław. The inside edge of the track is 400 m long. In each GNSS configuration, experimenters completed five laps on the second track, which was 407.67 m long.

Again, as before, different models of sports watches showed different accuracy depending on the selected constellation. The most precise result was the difference between the length of the treadmill and the measurement of the sports watch was 0.49 mwhich – in the researchers' opinion – is acceptable considering the low cost of the device with a GNSS receiver.

Results

This all confirmed that sports watches do not achieve extremely high accuracy compared to the results obtained with precision GNSS receivers. Some models provide distance measurement errors of less than one meter, while others are characterized by errors of even more than 20 meters in the same experiment. For positioning in two dimensions, the best watches provide an average error of 1.4 m, while the worst – 4.2 m.

Detailed results can be found in the mentioned study. Interestingly, it is difficult to point out a clear winner there, because the list of results was arranged slightly differently depending on the test. However, the most surprising thing is the measurement error of over 20 meters made by the Garmin Vivoactive 4s model.

As the researchers predict in their summary, “thanks to technological progress, also sports watches will be able to achieve higher accuracy in the future GNSS modules.