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b) real ground truth,
Hmm, I think the only truth would be that it was a bangle nearer the ground.
No, that is the idea of a) with the thesis that ankle is easier than wrist -which of cours is to bee seen and needs to be testet. I hope to see a much more robust outcome when varying parameters.
b) contains a bit of real ground truth! We have two acc input data streams a,b for which we know for sure that steps(a)-steps(b) =! 0. So even if we do not know the number of steps, we know that the bigger that difference is, the worse the algorithm "steps()" performs. No approximation here.
It is just a necessary, not a sufficient condition thought, so can not be used alone. E.g steps(x)=0 would be considered perfect but is completely useless obviously.
Still I think its a powerfull error measure, available with limited effort. If degenerate cases are excluded (eg. by demanding step count within +-20% of Mi/Fitbit or so) I would expect that to be a powerfull objective measure for guiding search.
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@HughB
I give any device I am going to compare against a test on a circuit that I know is 1.03m.
If it comes out around 2000 steps I know its accurate enough to use as a source of ground truth.
I usually do 2 or 3 tests on the same cicuit to establish reliability. I trust FitBit HR and Amizfit Bip to be accurate enough for what we need. I imagine other smart watches out there will be reasonably good as well, but you have to calibrate your measure first before using it as a yardstick.
Might be worth doing a 1 mile walk with the Run app v0.05 and checking how many steps are counted and distance is reported by the Mi5 band to see how accurate it is.
The idea of using another bangel running 'in development' software does not sound great as both measurements will be subject to version control and known issues. I think we either have to manually count the steps or use a known quantity (another sports watch that we have checked).
Hmm, I think the only truth would be that it was a bangle nearer the ground. Thats does not mean it will reliably count the steps any better. I would kind of expect the results of the B1 at ankle level to be better as the accelerometer swing will be much greater. However since the watch is going to be worn on the wrist tests have to be done with the measurement watch on the same wrist and accelerometer logs need to be done on the wrist as well otherwise they introduce another variable into the tests.