Protrack accuracy

[Sabrekakkonen 0]

What is pro track accuracy in measuring avarage fall rate and maxium fallrate? When mounted in helmet.

[pchapman 261]

I have mine on the outside of the helmet so I don't know if yours on the inside might take the edge off any fluctuations a bit better than has been my experience.

From a post of mine 10 years ago:

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1. Don't use the maximum speed. It often picks up unrealistic spikes.
2. Use the First Half average speed, not the Overall average speed because the latter tends to include too much of the bottom end of the dive, which may include unrealistic spikes.

Explanation:

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Regarding spikes in speed:

I find that the Protrack, mounted on the outside of my Protec helmet, often records a many-second long acceleration to a very high speed, like 155 mph, when starting to turn and track away from a belly fly formation.

Or, body position during a freefly jump can also cause spikes. For example, during head down practice where I was doing simple turns, and transitions to and from a sit, the Protrack recorded a couple big swings in speed. Supposedly down to 95 mph, and 7 seconds later, 185 mph SAS. I think not.

When calculating the average speed of the dive (or the first or second half of that), the first 15 seconds of the dive is excluded. That's great, as it pretty much excludes the period before terminal is reached.

But at the bottom end, only 7 seconds is excluded. That's far too little these days with high breakoffs, long tracks, and long snivels before one is slow enough to have the Protrack record that one has deployed. So the Protrack's overall average speed tends to include stuff at the bottom end one isn't trying to measure, including any unrealistic speed spike on breakoff.

(I find the Protrack is fine for long sustained tracks, just not for fast transitions into a track from other activity.)

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In other areas the Protrack is pretty good. I certainly see the difference in speeds between tandems with light, medium, and heavy people. Or the difference between an RW jump that felt fast, average, or floaty. I can see these differences even when just using the First Half speed, rather then checking Jumptrack graphs after the weekend.

As for that spike when I start to track, I know my track isn't diving or otherwise weird; I have been on various 50 -100 ways where such things might well be noticed. I think the sudden change of head position and body angle fools the device. Again, I don't know if having the Protrack inside the helmet might help.

[Sabrekakkonen 0]

What about avarage speed? Is accuracy +-10% or +-30 or what?