I bought the I-phone serve radar app

Discussion in 'Tennis Tips/Instruction' started by TheMagicianOfPrecision, Aug 8, 2011.

  1. Now where on the court shall I place it in order for it to "count" and be the most accurate !?

    The app has gotten lots of great rewiews and recommendations so I guess it is working really well.

    I will post the results on Thursday:

    Just for fun, plz post how fast you think i will hit! :)
     
    #1
  2. Laver777

    Laver777 Rookie

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    what app is it called? i wanna try it too. id guess probably place it in below the net in the middle? im not sure where they place pro raider guns
     
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  3. It is called speedClock, really cool!
    What if i misshit my serve :)?? That would not be cool...
     
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  4. Laver777

    Laver777 Rookie

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    cool.... ive allways wondered how fast i serve. is it reliable? lol, i hope you have insurance for your phone
     
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  5. Laver777

    Laver777 Rookie

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    #5
  6. 5263

    5263 G.O.A.T.

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    what is the method of measure?
    something with sound?
     
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  7. onehandbh

    onehandbh Hall of Fame

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    I think the speed it gives will have a large standard deviation (margin for error).
    It uses visual information to calculate the speed. The iphone's video camera
    doesn't have a fast enough shutter speed or high enough frame rate to be
    able to take a small slice of the trajectory of a tennis ball to make an
    accurate estimate.

    if you have a fast serve, it will be less accurate. More accurate for a slower serve.
    It iphone just doesn't have the capability to give the software precise information.
     
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  8. jdubbs

    jdubbs Hall of Fame

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    Have you tried it and found this to be the case? I was thinking about getting the app, but that would involve getting an iphone as well.
     
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  9. 5263

    5263 G.O.A.T.

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    That was pretty much my guess although, with the right functions, maybe it can compensate pretty well by measuring the blur etc...
    Still pretty big margin probably, as you said.
     
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  10. chollyred

    chollyred Rookie

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    Since the iPhone was a video recording rate of up to 30 FPS (determined by available light), and part of that is due to the speed at which it can write to disk, the software should be able to interpolate the trajectory of the ball and the speed between each frame captured (a time/distance calculator similar to how VASCAR works for catching speeders). I'd guess that it is fairly accurate. I'd love to hear some actual reviews.
     
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  11. papa

    papa Hall of Fame

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    yeah, me to - sound interesting. Is there a "total" apps package for all the tennis related stuff? Assume this stuff works on the tablets also.
     
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  12. onehandbh

    onehandbh Hall of Fame

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    Yes, it can interpolate and guestimate. Although it isn't as sexy, using
    sound is another way to measure speed. (sound of impact with racquet and
    court).

    I think the accuracy will increase if you move further back until you get the
    full court distance from racquet to impact in the service box is in the
    video frame.

    There was a software calculator someone on TW made that used # of
    frames in a 30fps video to calculate speed. Even being 1/2 of a frame
    off can make a big difference in speed. If you pick a smaller slice than
    the whole distance it gets worse.
     
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  13. stoneage

    stoneage Rookie

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    It records a a video of the event. Then it takes 5 frames and isolates the ball. You can the align the balls and speedClock calculates the speed. This is explained at the end of the video:

    It is measuring how many pixels the ball has moved between each frame, so it is not a question of hitting of missing a fame. You can determine the distance within 1 pixel, so if the ball moves 100 pixels between the frames that is a 1% error.

    However, you have to know the distance to the ball with reasonable accuracy to get good results.

    /Sten

    ______________________________________
    racquetTune, swingTool and netHeight, tennis apps for the iPhone.
     
    #13
  14. North

    North Professional

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    It would probably be getting great reviews if it was overestimating by 20+ mph and everyone thought their serves were faster than they really are. It wouldn't be working well but would get top marks for customer satisfaction - lol.
     
    Last edited: Aug 24, 2011
    #14
  15. d4o

    d4o New User

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    got the app. its garbage, it doesn't work
     
    #15
  16. mightyrick

    mightyrick Hall of Fame

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    LOL. For sure.
     
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  17. stoneage

    stoneage Rookie

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    Could you elaborate a little, what is not working?
     
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  18. dr325i

    dr325i Legend

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    It is showing that he cannot serve above 75 mph and he is sure he's hitting at 130!
     
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  19. FedExpress 333

    FedExpress 333 Professional

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    Hope it works, my guesstimation is 130MPH
     
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  20. psYcon

    psYcon Semi-Pro

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    Magician , did it work? I want to try it also. I think my serve max speed is around 110mph
     
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  21. Fedace

    Fedace Banned

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    What if you hit the iphone with your serve and it goes into 1000 pieces. would it be covered under warrantee ??
     
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  22. LeeD

    LeeD Bionic Poster

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    No BS here....
    I think MofP can serve right above 130 IF he flattened out his top/slice.
    As is, closer to 115-120 max.
     
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  23. stoneage

    stoneage Rookie

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    You are measuring from the side, so the risk is minor :)
    /Sten
    ______________________________________
    racquetTune, swingTool and netHeight, tennis apps for the iPhone.
     
    #23
  24. LeeD

    LeeD Bionic Poster

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    Still, nobody tried?
    I think it's impossible to get accurate readings from different people at different sites using exactly the same EQ. Just like theory is different from reality. Lab conditions are not directly applicable to the real world.
    I DO hope it works.
     
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  25. Bud

    Bud Bionic Poster

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    So??

    What was the result?
     
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  26. Timbo's hopeless slice

    Timbo's hopeless slice Hall of Fame

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    there was a radar on the show court of the last tournament I played.

    My best was a lowly 119 but I average about 112, I can live with that...

    (of course, on TT, I actually serve at 135!)
     
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  27. LeeD

    LeeD Bionic Poster

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    119 on one radar at one location MIGHT well be 135 from another radar at another location.
    You know DavisCup always produces the fastest serves.
    Now try serving in 52 degree weather with DunlopHDHardCourtChamp balls. Your 119 goes down to 109.
     
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  28. 5263

    5263 G.O.A.T.

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    112 mph is a pretty nice avg!
    Good show
     
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  29. I did try it 10 days ago, totally forgot to tell about it.

    It didnt work at all, good thing the price only was 0,99 USD.

    I had a friend of mine standing to the side, between the baseline and the service-line and i hit 10 serves. It showed everything from 75 mph-95 mph, no matter how hard i hit it wouldnt go over 95 mph :-? So...to the creator of the app, take it and stick it where the sun dont shine.
     
    #29
  30. papa

    papa Hall of Fame

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    Not exactly a "ringing endorsement" one way or the other.

    Even with pretty good radar guns the speed can and does vary depending on your location in relationship to the court, brightness, weather, new ball vs old ones, etc.

    For the serve, I've found one of the best spot is looking through the net at the server - still will vary but a lot more consistent.
     
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  31. I agree.

    But this was just way off, imagine you hit some of the hardest serves you have ever hit that you feel in your whole body down to your toes- and the damn machine shows 95 mph :) Yea...fun...
     
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  32. CDestroyer

    CDestroyer Professional

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    So whats the deal about the app only going up to 95 mph? Is that the limit or is the app not accurate? Please elaborate Stoneage.:smile:
     
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  33. LeeD

    LeeD Bionic Poster

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    Oh C'mon, MofP, I'm the naysayer of all time, and I give you 130 as is, more if you tried to flatten it out.
    And for comparison, I've been saying my serve is close to 100 flattened out, slower when hit with top/slice.
     
    #33
  34. luishcorreia

    luishcorreia Professional

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    #34
  35. Chas Tennis

    Chas Tennis Hall of Fame

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    Measuring ball velocities with Smartphones - Any updates?

    Has anyone got any updates on measuring serve ball velocities with the video camera of a Smartphone?

    This seems very feasible by simply putting in a scale to accurately get the distance along the ball's trajectory, make sure viewing angle is perpendicular to the ball's trajectory, etc. .

    I did read that the frame rates of some smartphones can vary from 30 fps and not be reproducible. ? Test somehow?

    100 MPH = 1760 inches/sec

    In 1/30 sec a ball with a velocity of 100 MPH ball would travel

    1760"/30 = 58.7"

    Might be better to use a camcorder or DSLR with a more telephoto lens. But in bright sunlight I believe that many smartphone video cameras use a fast shutter speed that reduces the motion blur on the ball.

    (It could be called the Pinocchio cam.)
     
    #35
  36. Limpinhitter

    Limpinhitter Legend

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    You're probably comparing apples and oranges. Unless it captures the highest speed after contact, it's not doing what the radar guns on the pro tour are doing.
     
    #36
  37. Jazzy

    Jazzy New User

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    Use the formula!

    I know that when we used to put the $150 radar gun at the center of the net on the other side, there is a formula that you have to use as the pros is taken right off of there racquet and not until it gets to the other side of the net. I want to say it was around a .25 additional mph per mph. So a 95 mph serve would have around 23mph added to it. Hope this helps!!
     
    #37
  38. Chas Tennis

    Chas Tennis Hall of Fame

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    (Not using the application in the OP but just any video camera.)

    A smartphone or camera could catch the ball image from the side close to impact. You would need two frames along the trajectory any time after the ball is struck.

    You need
    1) a scale placed along the trajectory and videoed before or after the serve.
    2) the time between frames (it should be 1/30 sec but it has to be checked?)

    V = distance traveled / 1/30 second

    It would be better to use a camera with a longer focal length lens and not have to worry whether the wide angle lens on a smartphone might cause some inaccuracy.
     
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