What the app measures, and why.
Three parameters, in the order the app explains them itself. Every chart here is calculated with the same formulas the app uses. Nothing is drawn in by hand.
Two settings. All target values.
How long the whole swing takes and how it splits between backswing and downswing. At 3 : 1 the downswing block fits three times into the backswing. Every other target value is calculated from these two settings.
The app does not round ratios that do not divide evenly: 2.5 × stays 2.5 ×.
On the App Store · Apple Watch required
The same two numbers as movement
The figure swings in the time set above and pauses briefly at the measuring points. Change the ratio and watch backswing and downswing shift against each other.
Nine key poses. The two that are measured are marked: the top ends the backswing, impact ends the downswing.
Nobody hits 0.30 s exactly.
Around every target value there is a band of ± 8 % with a fixed lower limit. For the 0.30 s downswing that is ± 24 ms. Inside the posts the swing counts, just outside is the middle grade, further out it is a miss.
The fine ticks are the measuring grid of the watch: one sample every 10 ms (100 Hz).
Why the total alone is not enough.
Tempo (the sum) and rhythm (the ratio) are derived values. Both can be right while each phase on its own is off. That is why the app assesses the two phases and not the total.
One sentence, not a score.
After the swing there is no score on the watch, but a sentence about the two measured phases:
Work through the derivation yourself,
at the tee.
On the App Store · Apple Watch required
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