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.