### Author Topic: About the hangtime based vertical jump calculators  (Read 8275 times)

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#### vag

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##### About the hangtime based vertical jump calculators
« on: December 22, 2009, 02:05:48 pm »
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Being an engineer i know well that the hangtime-vert calculation formula is 100% accurate, i even have my own excel version with the local gravity acceleration in the formula.
I was thinking:
The correct way to measure hangtime is to measure the time that the feet are in the air , from the first 'airborn' frame to the first 'touchdown frame'.
But doesnt that mean that we have a different measurement here compared to the normal one ( highest touch minus flat-footed reach )?
Instead of flat footed standing reach we are using 'toes-up' reach!
That would make the vertical measurements different by an amount equal to the flat-footed vs toes-up reach difference, wich would be ~4-5''.

woot

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##### Re: About the hangtime based vertical jump calculators
« Reply #1 on: December 22, 2009, 04:57:05 pm »
+1
Being an engineer i know well that the hangtime-vert calculation formula is 100% accurate, i even have my own excel version with the local gravity acceleration in the formula.
I was thinking:
The correct way to measure hangtime is to measure the time that the feet are in the air , from the first 'airborn' frame to the first 'touchdown frame'.
But doesnt that mean that we have a different measurement here compared to the normal one ( highest touch minus flat-footed reach )?
Instead of flat footed standing reach we are using 'toes-up' reach!
That would make the vertical measurements different by an amount equal to the flat-footed vs toes-up reach difference, wich would be ~4-5''.

well ya because, standing vert is a measure of how much your COM has changed from a flat-foot stand still.. so being up on the toes is changing the COM.. thats why in hangtime vids i always take the frame right before takeoff, still on the toes, but, right before your toes leave the ground.. this takes into account the 0.033s error also.. that gives you more of a vert number that is more similar to a vertec touch-reach.

the 0.033s error on takeoff and landing is the biggest concern with hangtime formula, when using 30fps cameras.. best case you're dead on, worst case you're 0.066s off.

ya it sux though i wish vertec's were ~20\$.. vert training with one is so much better.

#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #2 on: December 23, 2009, 04:48:09 am »
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Well i just got a new mobile that features 120fps video, that minimizes the error to 1/120 of a second each side , so max error is 1/60 wich is 0,016666.
I would still prefer the highest touch - standing reach measurement , but now highest touch is an aproximation , trying to see from the vid how much i got above a measured rim!
Im leaning towards the 120fps hangtime thing , jsut wanted your opinion.
Probably gonna use both in next jump session to compare the results, that should be interesting...
woot

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##### Re: About the hangtime based vertical jump calculators
« Reply #3 on: December 23, 2009, 05:28:49 am »
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Well i just got a new mobile that features 120fps video, that minimizes the error to 1/120 of a second each side , so max error is 1/60 wich is 0,016666.
I would still prefer the highest touch - standing reach measurement , but now highest touch is an aproximation , trying to see from the vid how much i got above a measured rim!
Im leaning towards the 120fps hangtime thing , jsut wanted your opinion.
Probably gonna use both in next jump session to compare the results, that should be interesting...

whoa.. awesome!!!!!!!!

120fps = fun fun fun.

cool man tell me how it goes.. with video timing, you can always take a few measurements... it would be interesting if you:

- calculated rvj using touch - reach .. touch on rim of course..
- compared that to: video timing of heels barely off ground AND toes FULLY extended right at takeoff... both timed until first contact with ground.

#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #4 on: December 24, 2009, 04:46:18 am »
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whoa.. awesome!!!!!!!!

120fps = fun fun fun.

cool man tell me how it goes.. with video timing, you can always take a few measurements... it would be interesting if you:

- calculated rvj using touch - reach .. touch on rim of course..
- compared that to: video timing of heels barely off ground AND toes FULLY extended right at takeoff... both timed until first contact with ground.

My thoughts exactly , word by word!
Gonna have an ultra-epic "hangtime calculation vs reality" video up soon!

lolzzzzzz @ psyience detective
woot

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##### Re: About the hangtime based vertical jump calculators
« Reply #5 on: December 24, 2009, 05:39:58 am »
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whoa.. awesome!!!!!!!!

120fps = fun fun fun.

cool man tell me how it goes.. with video timing, you can always take a few measurements... it would be interesting if you:

- calculated rvj using touch - reach .. touch on rim of course..
- compared that to: video timing of heels barely off ground AND toes FULLY extended right at takeoff... both timed until first contact with ground.

My thoughts exactly , word by word!
Gonna have an ultra-epic "hangtime calculation vs reality" video up soon!

lolzzzzzz @ psyience detective

nice! cant wait to check it out

should be cool

lol @ psyence detective, he got 90 days in jail... i thought he'd get alot more to be honest.. at least more than a year.

#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #6 on: December 26, 2009, 03:57:41 pm »
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As i expected , i busted that hangtime calculation shit:

EDIT ( 6 years later  ):

The video does not exist anymore so i should describe what it showed.
I captured a jump that i knew exactly how high i got ( highest touch - standing one hand flatfooted reach ) , it was 24''.
The hangtime calculator was wrong , measuring either from toes off or from heels off.
What seemed to work was use the hangtime calculator measuring the toes-off-to-touchdown hangtime, and then add the 'reach on toes - reach flatfooted' correction, see continued discussion below.
« Last Edit: November 11, 2015, 06:33:34 am by vag »
woot

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##### Re: About the hangtime based vertical jump calculators
« Reply #7 on: December 27, 2009, 10:07:06 pm »
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As i expected , i busted that hangtime calculation shit:

interesting.. what was 'almost flat foot' as the starting point.. ? should be pretty close..

cool vid.

peace

#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #8 on: December 28, 2009, 05:19:22 am »
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As i expected , i busted that hangtime calculation shit:

interesting.. what was 'almost flat foot' as the starting point.. ? should be pretty close..

cool vid.

peace

Flatfoot to touchdown hangtime was also wrong, its too early. The correct timeframe start seemed to be somewhere the 1st and 2nd visible heel elevation. Cant make any rule out of that.
What seems to be true is that the hangtime calculator measures the highest touch - reach on your toes.
So the error is equal to the flatfoot/toes reach difference, as i was speculating on my first qm. That is indeed 5'' for me , makes sense.
woot

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##### Re: About the hangtime based vertical jump calculators
« Reply #9 on: March 10, 2010, 03:05:34 pm »
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What is strange about this is that the just jump mat via it's patent filing uses a standard hangtime calculator, yet, it consistently reads slightly higher than what my vertec jump is when I measured them simultaneously. From your video, I should have seen a drastic decrease in my vertical, yet I saw a slight bump.

#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #10 on: March 10, 2010, 03:15:43 pm »
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What is strange about this is that the just jump mat via it's patent filing uses a standard hangtime calculator, yet, it consistently reads slightly higher than what my vertec jump is when I measured them simultaneously. From your video, I should have seen a drastic decrease in my vertical, yet I saw a slight bump.

I thought of that too. I can only speculate this:
jumpmat , through getting readings all the time, starts timing not from take-off ( when force is 0 ) but from the peak of the force applied. That would probably be with feet still on the ground. Maybe my correction speculation ( correction = toes up reach - flatfooted reach ) is wrong , and the correct correction is that.
Or maybe ( i highly doubt that ) it just uses some standard correction like 5'' which would be correct in more cases but not in all.
Anyway i was not refering to jumpmat , im sure its pretty accurate , i was refering to counting time/frames in the air and calculating your jump from that with the hangtime calculation...
woot

#### Dreyth

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##### Re: About the hangtime based vertical jump calculators
« Reply #11 on: January 30, 2016, 03:51:23 pm »
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bump for more input from people

i want to get to the bottom of this

wish we had a 240fps camera (actually i think my iphone 6s does that) and did a bunch of measured jumps and graphed the (touch - reach) against (toes off ground - toes on gound) and also against (flat foot - flat foot) and found average corrections for them. maybe also see if the correction is the same as (reach on toes - reach flat footed)
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#### vag

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##### Re: About the hangtime based vertical jump calculators
« Reply #12 on: January 31, 2016, 04:53:13 am »
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Iphone 6s does have high frame video, don't expect huge differences though, when you are between , say 24 and 25 frames at a 30 frame video, the 240 frames will only tell you it was 24,3 , no big deal. The other errors in that measurement ( knee angle at landing, horizontal displacement ) are more significant.
You can always use the hangtime as an indicator, but stick to the highest touch for accurate measurement.
woot

#### Dreyth

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##### Re: About the hangtime based vertical jump calculators
« Reply #13 on: January 31, 2016, 10:03:09 am »
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Iphone 6s does have high frame video, don't expect huge differences though, when you are between , say 24 and 25 frames at a 30 frame video, the 240 frames will only tell you it was 24,3 , no big deal. The other errors in that measurement ( knee angle at landing, horizontal displacement ) are more significant.
You can always use the hangtime as an indicator, but stick to the highest touch for accurate measurement.
Agreed. My current gym doesn't have a single good spot to test highest touch There is this one pipe running below the ceiling that I can only touch on my best SVJ days, and it happens to be a good goal to aim for though. Sooner or later I'll be able to get it almost every workout. Damn I miss having a gym with a basketball court in it...
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