Race 2: wrong cadence/step calculated during activities

jjpaz

Technical Discrepancy Report: Internal Logic Error in Cadence Averaging (Suunto Race 2)

The data recorded by the Suunto Race 2 during the 62:38 session shows a critical mathematical inconsistency between ‘Total Strides’ and ‘Average Cadence’.

Activity 1:
Race 2: 11,21km. 10639 steps. 87rpm. 1h02’38"
Verttical: 11,26km. 10647 steps. 85rpm. 1h02’37"

The device recorded a total of 10,639 steps. Mathematically, over a duration of 62.63 minutes, this results in an actual cadence of 169.8 spm (84.9 rpm). However, the watch reported an Average Cadence of 87 rpm (174 spm). For this average to be correct, the device should have registered approximately 10,900 steps, which is not the case.

Activity 2:
Race 2: 9,02km. 8736 steps. 87rpm. 51’14".
Race S: 9,08km. 8743 steps. 86rpm. 51’12".

On Jan 18th (51:14 duration), the Race 2 recorded 8,736 total steps, which mathematically results in 85.25 rpm. However, the device reported an Average Cadence of 87 rpm. In contrast, the Suunto Race S on the same run recorded 8,743 steps (85.35 rpm) and correctly reported 86 rpm.

This proves that the Suunto Race 2 is not deriving its ‘Average Cadence’ from the ‘Total Strides’ counter. Instead, it is using incorrectly averaged instantaneous values. This ‘ghost cadence’ (87 rpm vs. the real 85 rpm) directly can mislead the FusedSpeed algorithm: the watch ‘believes’ the runner is taking more steps than they actually are, assumes a much shorter stride length, and consequently can apply an artificial reduction to the total distance (11.21 km vs. the 11.26 km recorded by the Suunto Vertical).

This behavior is replicated in every activity and maybe is related to that Suunto Race 2 systematically under-reports total distance by 0.5% to 1.5% compared to reference devices (Suunto Vertical and Suunto Race S).

Dimitrios Kanellopoulos

Did you pause?

jjpaz

@Dimitrios-Kanellopoulos said in Race 2: wrong cadence/step calculated during activities:

Did you pause?

No, no pause at all. Continuous activity.

gkaempfer

@jjpaz this sounds related to this similar issue I observed on my V2 where step count and step length don’t add up. See https://forum.suunto.com/topic/14291/steps-x-avg-step-length-distance

jjpaz

@gkaempfer said in Race 2: wrong cadence/step calculated during activities:

@jjpaz this sounds related to this similar issue I observed on my V2 where step count and step length don’t add up. See https://forum.suunto.com/topic/14291/steps-x-avg-step-length-distance

Maybe you can verify your cadence/step data according your activities duration and see if also discrepancy exists.

jjpaz

@gkaempfer said in Race 2: wrong cadence/step calculated during activities:

@jjpaz this sounds related to this similar issue I observed on my V2 where step count and step length don’t add up. See https://forum.suunto.com/topic/14291/steps-x-avg-step-length-distance

According to my last activity data, Race 2:

Distance: 9.02 km.
Steps: 8736
Avg.step length: 101 cm

8736 * 101 = 8.823 km

Same activity, Race S:

Distance: 9.08 km.
Steps: 8743
Avg.step length: 103cm

8743 * 103 = 9.005 km.

WOW.

Maybe this is also related to my “Race 2” cutting distances isssue.

Dimitrios Kanellopoulos

@jjpaz

We do not calculate cadence (rpm) or step cadence (spm) based on total steps (which in some devices has some machine learning to avoid ie steps from the backpack S3 watches mainly in the past) divided by activity duration. Instead, cadence is derived directly from the cadence data.
Using steps divided by duration to back-calculate cadence is more prone to errors, as the recorded step count can occasionally be higher or lower than the actual value.

yes we have a quite good cadence (instant) calculation but lets say it like this, steps do not come from cadence.

jjpaz

@Dimitrios-Kanellopoulos said in Race 2: wrong cadence/step calculated during activities:

@jjpaz

We do not calculate cadence (rpm) or step cadence (spm) based on total steps (which in some devices has some machine learning to avoid ie steps from the backpack S3 watches mainly in the past) divided by activity duration. Instead, cadence is derived directly from the cadence data.
Using steps divided by duration to back-calculate cadence is more prone to errors, as the recorded step count can occasionally be higher or lower than the actual value.

yes we have a quite good cadence (instant) calculation but lets say it like this, steps do not come from cadence.

OK, so they are not directly related and are independently calculated, isn´t it? Good to know.

What confused me is that both watches calculate the same steps but the cadence differs by 2 rpm between them.

Thanks for the information!