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Tracking an object moving away from camera - May 30 at 5:56PM
Chris Fortunato
3 Posts

I'm conducting research on the Magnus effect and would like to use the Tracker software (which is awesome by the way) to determine critical attributes of the trajectory of a spinning ball in flight (velocity, curve, and distance to the break point of the curve).  To capture the all the motion of the ball the best position for the camera is behind the point of origin facing the direction of travel.  Picture a camera behind a pitcher facing the catcher.

Velocity and curve has been fairly easy to determine thanks to the tutorials, community and simplicity of the Tracker software. With this perspective, I've been unable to accurately determine distance of the ball over time.

Any thoughts or suggestions would be most welcome.

My thanks,

Chris


Replies to Tracking an object moving away from camera

Re: Tracking an object moving away from camera - Jun 03 11:56AM
Douglas Brown Avatar
Douglas Brown
161 Posts

Hi Chris,

I don't really see how you're going to accomplish this unless the ball is large enough to track the changes in its angular size and determine distances from that.  Moving directly away from the camera is the worst possible angle for x-y tracking which looks only at motion in a plane perpendicular to the camera view.  Can you also record it with a second camera on one side?

Doug


> Re: Tracking an object moving away from camera
>
> I'm conducting research on the Magnus effect and would
> like to use the Tracker software (which is awesome
> by the way) to determine critical attributes of the
> trajectory of a spinning ball in flight (velocity,
> curve, and distance to the break point of the curve).
>  To capture the all the motion of the ball the best
> position for the camera is behind the point of origin
> facing the direction of travel.  Picture a camera
> behind a pitcher facing the catcher.
>
> Velocity and
> curve has been fairly easy to determine thanks to
> the tutorials, community and simplicity of the Tracker
> software. With this perspective, I've been unable
> to accurately determine distance of the ball over time
>
>
> Any thoughts or suggestions would be most welcome
>
>
> My thanks,
>
> Chris



Re: Re: Tracking an object moving away from camera - Jun 06 11:12AM
Chris Fortunato
3 Posts

Doug,

Thank you for the response.  For my next test I'm going to attempt to have multiple cameras recording the trajectory (from above looking down and perpendicular to the flight path).  Thanks for the advice!

Regards,

Chris



Re: Tracking an object moving away from camera - Jun 05 1:05AM
lookang Avatar
lookang
190 Posts

my suggestion

you probably need another top plane camera aiming at the motion of the ball, in addition to the back camera that you have. with 2 videos sync up and analyzed as separate video in Tracker, it may be possible to get some useful data.

my thoughts

it sounds like a difficult task to do in Tracker since Tracker is fantastic for 2D motion when camera facing it directly. :)

 http://iwant2study.org/ospsg/index.php/interactive-resources/physics/02-newtonian-mechanics/02-dynamics/196-frisbee-motion

 

Post edited June 5, 2017 at 1:08 AM EST.


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Re: Re: Tracking an object moving away from camera - Jun 06 11:17AM
Chris Fortunato
3 Posts

Lookang,

Thank you very much for your reply.  I'm going to follow the advice you and Doug have provided and utilize a different (and multiple) camera angles.

My thanks for your help!

-Chris



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