Video analysis using a shaking camera

• Main Author: de Jesus,V. L. B.
• Publication Date: 2021
• Other Authors: Sasaki,D. G. G.
• Format: Article
• Language: eng
• Source: Revista Brasileira de Ensino de Física (Online)
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1806-11172021000100479
• topic: Physics teaching; reference frame; relative movement; video analysis; Tracker

To perform a reliable video analysis, it is mandatory to avoid shaking the camera while taking the video, normally using a tripod for smartphones/cameras. But there are some situations which the only chance to make the video is using your hands and it is almost impossible to avoid shaking the camera even trying your best. Imagine the following situation: a volleyball is obliquely launched, and the video is filmed by hand. Then, a point that is fixed in relation to the ground is chosen as the origin of a ground fixed reference frame. Despite being a ground fixed point, it will appear shaky in images captured by the handheld camera. Thereby, two standard video analyses are performed, one from the ground fixed point random shaking and one from the ball’s trajectory, both in relation to the default reference frame of the video analysis software. Lastly, to implement the video analysis of the relative ball movement it is enough to subtract the position coordinates of the ball’s movement by the position coordinates of the ground fixed point tremble, at each instant of time. The graphs of the position and velocity components versus time are presented, and the results are discussed.