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Problems with high frame rate and autotracker
S Davis
1 Posts

Hello I've been using Tracker for some time with students and the first thing we do is analyse projectile motion and get a value of g (ay) to show it's downwards and always about the same. I tell them to use high frame rates for the video and a blank background for auto tracking. We have a video with 240fps that's nice and smooth but the autotracker seems to be giving enough variation between matches on each frame to create very poor acceleration vectors compared to a 30fps video.


Replies to Problems with high frame rate and autotracker

Re: Problems with high frame rate and autotracker -
Douglas Brown Avatar
Douglas Brown
388 Posts

Assuming the absolute uncertainties dx in the position measurements are the same, then higher frame rates, which give smaller displacements per step ("disp"), will automatically result in larger relative uncertainties (dx/disp). This is why the velocities and accelerations have more noise.  


> I've been using Tracker for some time with
> students and the first thing we do is analyse projectile
> motion and get a value of g (ay) to show it's downwards
> and always about the same. I tell them to use high
> frame rates for the video and a blank background for
> auto tracking. We have a video with 240fps that's
> nice and smooth but the autotracker seems to be giving
> enough variation between matches on each frame to
> create very poor acceleration vectors compared to
> a 30fps video.



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