[michaelt]

It's actually fairly easy, for things like running GPSes.

You know the track isn't snapped to a map. And you know it's not built into a car, so no odometer or rate gyro.

Then just look at the trace as the sportsperson goes around a corner. Does the trace overshoot, then backtrack? That means the kalman filter is heavily smoothing with momentum. Does it produce a gently rounded corner that goes through a building? That means there's a moving average.

However if the traces display sharp corners when appropriate - then the signal is not being excessively smoothed.

(And I can assure you, even if a GPS watch has enough motion sensing to count steps, the swinging of arms and bouncing of feet mean wrist acceleration is noisy enough you've got no chance of detecting a runner turning a corner)

[icegreentea2]

Right, I was mostly thinking about robustness against transient jumps due to transient multipath reflection as you navigate around an urban environment. If you know that your strapped to a walker/runner, you know that you can't travel 100m in ~3-4 seconds.