Kinovea Sports Analysis Software

Discussion in 'Tennis Tips/Instruction' started by Chas Tennis, Oct 2, 2012.

  1. Chas Tennis

    Chas Tennis Hall of Fame

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  2. janm

    janm Rookie

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    I just downloaded this a few hours ago and think its great.

    I'm wondering how one figures out the correct amount of lead tape to add to a racket?

    I know I can't do it by feel. Only when adding a lot, probably way more then I should I start feeling the effects.

    Would using software like this introduce a more scientific way of measuring the perfect amount of lead tape to use.

    ie. could this software measure racket head speed so I can figure out the point where the weight slows head speed down too much?

    Anyone know how do the proffessional companies do these type of measurements?
     
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  3. Chas Tennis

    Chas Tennis Hall of Fame

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    Kinovea is an excellent tool for analyzing stroke videos!

    There are discussions of lead tape in the "Other Equipment" forum.
     
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  4. Greg G

    Greg G Professional

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    I agree, Kinovea is very helpful! I'm sure I've only just scratched the surface with slow motion and annotation. Thanks for pointing me to it (in another thread).
     
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  5. Chas Tennis

    Chas Tennis Hall of Fame

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    Good problem but you would have to figure out what you want to measure and apply the Kinovea software.

    Kinovea tracking a ping pong ball marker on a tennis racket.
    https://vimeo.com/25144725

    Velocity - https://vimeo.com/49909907 Put a scale in the video and you can measure velocity if a few geometric factors are properly considered.

    Here is some more serious tennis research by the ITF.
    http://www.itftennis.com/technical/research/lab/spin/

    Also look up the work of Rod Cross on rackets, ball spins, kick serve, etc.

    Vicon is a company that does 3D high speed video for motion capture. These $300K multi-camera systems are used to capture the movements of people wearing reflective markers for making video games and computer animations. The same 3D system might be used to get the complete motion of tennis rackets impacts with various amounts of lead tape.

    I don't know much about lead tape but reducing the racket axial rotation on impact by placing lead tape on the side edges is probably an important use. ? They say that rotation around the racket axis makes no difference because the ball leaves the strings in just 5 milliseconds but I'm not sure of that conclusion.

    See forehand racket face hits at the bottom of the webpage
    http://blog.tennisspeed.com/2011_01_01_archive.html
     
    Last edited: Oct 3, 2012
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  6. Greg G

    Greg G Professional

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    Great idea on the ping pong ball! I've been trying to wear bright wristbands, but yes the background is a big factor when it loses 'lock' on the object/part you're tracking.

    Maybe I'll take one for the team and show up on the court all decked out in ping pong balls :)
     
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  7. janm

    janm Rookie

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    I thought I could measure racket head speed upto contact.

    Using the ping bong ball it looks like i'd be able to make a measurement on this. The swing path is a 3d path and i'd only be able to measure in one axis so I won't get accurate acceleration at different points on the swing path. I can get an average speed thought which will probably be enough.

    I'd just like to determine the swing weight I can manage first and then figure out optimum lead placement.
     
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  8. Greg G

    Greg G Professional

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  9. Chas Tennis

    Chas Tennis Hall of Fame

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    http://blog.tennisspeed.com/2011/05/roadmap-to-hall-of-fame-forehand-part-1.html

    I like these displays of racket head speed and orientation. With Kinovea you can go frame by frame and add the racket face lines manually. Lead tape on the edges would change the tilt after off-center impacts. How much?

    Off center impacts causing racket face rotation -
    http://www.youtube.com/user/misutaroboto/videos?view=0

    A single camera cannot do 3D measurements. From a distance and for object motions parallel to the sensor plane it can measure X & Y pretty well. The component of the object's velocity that is toward or away from the camera, call it Z, cannot be measured. With some judgement you can often get some measurements and make the errors small.
     
    Last edited: Oct 3, 2012
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  10. janm

    janm Rookie

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    Hi Chas,

    I was looking at that app a few days ago, its based on math so don't know how accurate it would be to the real world swing weights of rackets but it does allow you to gauge how a racket may change with customizations.

    I did enjoy the tennisspeed blog article a have been wanting to do something similar but I need to get hold of a higher rate camera then i've got at the moment.

    The video below is what I was thinking about doing. I think its just distance over time measurements at various points of the swing. One could do this quite easily using the stop watch function and the size measure tool (measure racket size) for scale in the Kinovea software.

    http://www.youtube.com/watch?v=siscoYKyEr0&feature=plcp

    I can start adding lead and take a few measurements to get an average and then repeat this for a few iterations till that racket head starts slowing.

    At the moment i'm using an APD and it feels light as a feather so I know I definately can add some weight. I just don't want to add too much as mess up my stoke.
     
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