A while back i posted a thread on a program designed to analyze and predict the motion of a pendulum. Now i need to set up an experiment to test the program. For those who don't remember/didn't see the last thread, the program can predict the motion of the pendulum at any time in its swing, though its accuracy is unknown, hence the purpose of the experiment. I need to somehow devise a method for measuring the position of the swinging pendulum, i have easy access to a video camera for frame by frame analysis, as well as a strobe light that i can set to a speicific number of flashes per minute. The best idea i could come up with was to use a poster board back drop with gradations marking where the pendulum should be at certain time intervals from release (the markings would be based upon the programs predictions) and then compare the pendulums position on the video with the markings. I was thinking due to an issue with perspective (the distance between the pendulum and the markins combined with the wide displacements i planned on testing would cause the same problem as a measuring cup with gradations located on the outside) parallax measurements could be necessary in order to calculate the actual position to then compare with the data. Any other ideas?