Re: software for measurements from video images?

[Leigh Palmer <palmer@sfu.ca>]

> I did check the timing between the frames and found it to practically the
> same as it should be, 30 frames per second. The errors come from finding
> positions and they result in fluctuations of accelerations which are at
> least as large as 30% or so. Filming sidewise does help a little. We are
> depending on differences of small differences and errors as small as one
> pixel, or one line, are significant.

Yes, and if you recognize that then you must recognize that you should
not have points on your graph; you should have bars representing your
uncertainties. Do you still have problems when this change is made?

I found no difficulties with the video kinematics when I used a high
"shutter speed" on my Canon A-1 digital. I wasn't measuring g, however;
I was doing rotational measurements. Uncertainties must be considered
whenever any physical measurement is made. The uncertainties here are
built-in and readily calculated.

Leigh