Race 2 accuracy
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@LGoSo I think there would be three points to consider here:
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As I understand it, the model is a Rolson 50799. The manufacturer doesn’t specify its accuracy, but in that price range, I believe it will be between 0.1% and 0.5% (meaning the margin of error would be between 0.5 m and 2.5 m over a distance of 500 m).
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For such uneven terrain, a wheel with a circumference of around 1 m might not be the most suitable option; for these cases, measuring wheels with a circumference of around 2 m are used.
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If the terrain has a noticeable slope, as seems to be the case, we wouldn’t just be assessing the accuracy of the watch’s GNSS, but also that of its altimeter. (In reality, the distance should be compared against the result of using the ‘3D Distance’ option on the watch, which I assume Suunto uses by default since it isn’t available as a toggle.)
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@chus1962 Another possible source of discrepancy is that in trail running you are on an uneven ground. The real distance between two steps can be slightly higher than the GPS distance. Again, to fix order of magnitude, if you compare a flight distance to an undulating terrain but this time with a difference of 5cm every 1m, there is a difference of 0.6%. But this time the GPS would be less accurate than the wheel.
And another one is how the altitude is managed by the watch. If the altitude is not correct, the watch is going to correct it but slowly in the first hour of the activity (or whatever is implemented). If the correction is taken as the real altitude, a false 3D distance could be estimated. I have a similar issue with the NGP on my coros with flat sections that are considered sloppy because I forget to adjust the real altitude at the start of the activity.
And about the wheel accuracy, the one given by the constructor is valid for a new wheel. If the wheel is not new, this number could be (quite) different.(I am not a specialist of whatever is discussed here. Just free thinking…)
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this discussion is getting very academic.
I don’t see the practical use of 1cm stones for the wheel and micro climbs when stepping on a stone.
I think this is more about different models agreeing when taken on the same activity.Race 2 due to design has been measuring short in some cases.
This will be changed with the next firmware for Race 2. -
@Egika In the post of Joaquín, there is a discrepancy between GPS of all watches and the wheel that was supposed to be the “true”. I just add some hypothesis that could question the fact that the wheel is the “true” distance and avoid that anyone could conclude from the test of Joaquín that all GPS watches are wrong.
Personally I don’t care too much about the GPS distance and don’t understand why people is worried about this tiny race 2 discrepancy. To each his own… -
@LGoSo On the same boat, mostly in this thread for fun, do not care about the “short” measurements, that actually makes me run faster to get the same numbers
But GPS will never be “true” measurement, especially on hilly terrain, since it is only GPS coordinates. So measuring wheel will always be “true” distance regardless of small inaccuracies. -
for those of us who train with intervals at specific paces in areas with good GPS reception and smooth surfaces, a difference like the current one of 2 to 5 seconds per kilometer is a significant error that distorts the progress of a training session, and going faster isn’t always the goal.
I understand that people who use their watches for hiking or who don’t care about pace might find this ridiculous, but I would ask those people to be understanding of those of us with other needs. -
@isaac.net at the end its called Race not Hike
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@isaac.net I completely agree with the importance of those pace errors. However, before the Race 2, I used a Race S. I regularly train on measured loops, so I know the discrepancy between the distance meassured by the watch and the actual distance. What catches my attention about this matter is that the underestimation errors in distance measurement with the Race 2 are similar to, or perhaps even smaller than, the overestimation errors I had with the Race S, and nobody ever complained about the Race S.
However, beyond the final error, I’ve had the feeling of irregular behavior in the distance measurement in the Race 2, the correction is certainly welcome.
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@chus1962 In this thread there are several users that did comparisons using a Race S and they are only finding discrepancies with the Race 2 but not the Race S
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@dreamer_ Just speaking from my own experience, which is the result of numerous repetitions, but yeah, under my own training conditions.
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@isaac.net I totally understand your needs but at least for me GPS is not usable for speed during (short) intervals even with good reception. I use a stryd pod for the speed. GPS derived speed is not stable enough.
But I don’t have a recent watch so perhaps it is usable now.
Personally, I don’t care being 2 to 5 seconds faster or slower than intervals specified speed. The reason is that usually the speed that has been asked for running the interval is an estimation based on previous races or tests. But those tests/races have also some uncertainty (temperature, sleep, improvement since the tests, …). I am pretty sure that two VO2Max speed tests realized back to back (with appropriate days rest in between) would give most of the time results with higher difference than 2%. Without talking about the accuracy of the instruments which is around 3% meaning that if you change the test laboratory (or the testing track), the results could be up to 3% different. So, to some margin (around 10’/km) I adapt my speed up or down according to my current feeling. I think that precision is more valuable than accuracy and for short intervals GPS speed is neither of them. Just my opinion…
