Hello, I have a question to ask the group regarding speed. I wanted to know what function is behind the calculation of speed, since using the function "square root ((x1-x2) squared + (y1-y2) squared) / time x 3.6 = Km / h" and substituting the data in the report (xyt) do not get the same speed value that the software gives me automatically
- joan
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For the point at frame i, it uses the positions at frames i-1 and i+1 and divide by 2 time intervals.
Also depending on where you are looking the speed is calculated using either the raw positions or filtered positions. If you use the Linear Kinematics dialog it uses the filtered values unless you have disabled filtered in the preferences.
Hi Joan, many thanks for your answer.
Cause of I'm not familiar with this kind of topic, may you explain me, in a very easy way, which is the advantage in using the filtered positions?
In addition, starting simply from the (x) and (y) coordinates, which are the law/rules that Kinovea uses for the calculation of the speed? I've tried to calculate the speed using the formula space/time but the obtained values are a little bit different from those I read on the software.
Finally, I've verified that calculations are more correct if I take them nearby the perpective grid (used for the calibration of the images). Is it right?
Thanks for your kind assistance.