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Leaderboard Speed?

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flag kevinthestout
Posted: May 7, 2025 at 21:33 Quote
Can anyone tell me what "speed" refers to on the TF leaderboards?

It's not max speed - it's never close to the max speed reported by Strava.

It can't be mean speed with respect to time since the speeds are not monotonically decreasing with place e.g. sometimes the 3rd place speed is faster than the 2nd place speed.

It doesn't seem to be mean speed with respect to distance since sometimes the speed reported is less than the speed which would correspond to mean speed with respect to time. I believe it's mathematically impossible for mean speed wrt distance to be less than mean speed wrt time.

What other 'speed' statistic would be relevant here?
flag BenLow2019
Posted: May 8, 2025 at 5:48 Quote
kevinthestout wrote:
Can anyone tell me what "speed" refers to on the TF leaderboards?

It's not max speed - it's never close to the max speed reported by Strava.

It can't be mean speed with respect to time since the speeds are not monotonically decreasing with place e.g. sometimes the 3rd place speed is faster than the 2nd place speed.

It doesn't seem to be mean speed with respect to distance since sometimes the speed reported is less than the speed which would correspond to mean speed with respect to time. I believe it's mathematically impossible for mean speed wrt distance to be less than mean speed wrt time.

What other 'speed' statistic would be relevant here?

Looking at just one trail on TF and considering the issue I think I know the math:
Leaderboard uses the length of the trail and the time that the rider was on the trail to solve MPH. Therefore the rider with the lowest time will have the highest MPH and the Leaderboard is arranged accordingly. TF rounds the numbers to the nearest whole value.
Convert the trail distance to miles. Convert the time on the trail to hours. Calculate the speed by dividing the "miles" of the trail by the "hours" spent on the trail to get the MPH during the ride on that trail.
I did this with a few of the values on the Leaderboard for the pictured trail and it was in the ballpark.
photo
flag BenLow2019
Posted: May 8, 2025 at 6:12 Quote
After posting above I looked at a few more trails and most are fairly accurate with my assessment. But then I found one that was different and more like your description wherein some times and speeds were out of order on the Leaderboard. I think it boils down to sloppy rounding or sloppy math overall on the part of the MPH calculation. In the picture below you can see that the rider times are all in order, but the MPH is out of order. The rider at the top had the fastest time, but the MPH is lower than the bottom rider. I think the math is bad on some Leaderboards.
photo
flag kevinthestout
Posted: May 8, 2025 at 22:40 Quote
It could be that the calculation is using the length of the riders track between the start gate and the finish gate rather than the true length of the trail. GPS error means the riders track could be either longer or shorter than the trail length.
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